diff options
| -rw-r--r-- | bash.html.markdown | 12 | ||||
| -rw-r--r-- | go.html.markdown | 10 | ||||
| -rw-r--r-- | java.html.markdown | 2 | ||||
| -rw-r--r-- | perl6.html.markdown | 1229 | ||||
| -rw-r--r-- | pt-br/markdown-pt.html.markdown | 251 | ||||
| -rw-r--r-- | python.html.markdown | 31 | ||||
| -rw-r--r-- | python3.html.markdown | 35 | ||||
| -rw-r--r-- | zh-cn/julia-cn.html.markdown | 729 |
8 files changed, 2275 insertions, 24 deletions
diff --git a/bash.html.markdown b/bash.html.markdown index 15d1c068..845ebead 100644 --- a/bash.html.markdown +++ b/bash.html.markdown @@ -7,6 +7,7 @@ contributors: - ["Alexandre Medeiros", "http://alemedeiros.sdf.org"] - ["Denis Arh", "https://github.com/darh"] - ["akirahirose", "https://twitter.com/akirahirose"] + - ["Anton Strömkvist", "http://lutic.org/"] filename: LearnBash.sh --- @@ -81,6 +82,17 @@ fi echo "Always executed" || echo "Only executed if first command fails" echo "Always executed" && echo "Only executed if first command does NOT fail" +# To use && and || with if statements, you need multiple pairs of square brackets: +if [ $NAME == "Steve" ] && [ $AGE -eq 15 ] +then + echo "This will run if $NAME is Steve AND $AGE is 15." +fi + +if [ $NAME == "Daniya" ] || [ $NAME == "Zach" ] +then + echo "This will run if $NAME is Daniya OR Zach." +fi + # Expressions are denoted with the following format: echo $(( 10 + 5 )) diff --git a/go.html.markdown b/go.html.markdown index a1be08af..656b1051 100644 --- a/go.html.markdown +++ b/go.html.markdown @@ -177,6 +177,14 @@ func learnFlowControl() { break // Just kidding. continue // Unreached. } + + // You can use range to iterate over an array, a slice, a string, a map, or a channel. + // range returns one (channel) or two values (array, slice, string and map). + for key, value := range map[string]int{"one": 1, "two": 2, "three": 3} { + // for each pair in the map, print key and value + fmt.Printf("key=%s, value=%d\n", key, value) + } + // As with for, := in an if statement means to declare and assign // y first, then test y > x. if y := expensiveComputation(); y > x { @@ -378,6 +386,8 @@ There you can follow the tutorial, play interactively, and read lots. The language definition itself is highly recommended. It's easy to read and amazingly short (as language definitions go these days.) +You can play around with the code on [Go playground](https://play.golang.org/p/tnWMjr16Mm). Try to change it and run it from your browser! Note that you can use [https://play.golang.org](https://play.golang.org) as a [REPL](https://en.wikipedia.org/wiki/Read-eval-print_loop) to test things and code in your browser, without even installing Go. + On the reading list for students of Go is the [source code to the standard library](http://golang.org/src/pkg/). Comprehensively documented, it demonstrates the best of readable and understandable Go, Go style, and Go diff --git a/java.html.markdown b/java.html.markdown index 50875491..3484aee5 100644 --- a/java.html.markdown +++ b/java.html.markdown @@ -103,7 +103,7 @@ public class LearnJava { //The array size must be decided upon instantiation //The following formats work for declaring an arrow //<datatype> [] <var name> = new <datatype>[<array size>]; - //<datetype> <var name>[] = new <datatype>[<array size>]; + //<datatype> <var name>[] = new <datatype>[<array size>]; int [] intArray = new int[10]; String [] stringArray = new String[1]; boolean boolArray [] = new boolean[100]; diff --git a/perl6.html.markdown b/perl6.html.markdown new file mode 100644 index 00000000..92219708 --- /dev/null +++ b/perl6.html.markdown @@ -0,0 +1,1229 @@ +--- +name: perl6 +category: language +language: perl6 +filename: learnperl6.pl +contributors: + - ["Nami-Doc", "http://github.com/Nami-Doc"] +--- + +Perl 6 is a highly capable, feature-rich programming language made for the upcoming hundred years. + +Perl 6 runs on [the Parrot VM](http://parrot.org/), the JVM and [the MoarVM](http://moarvm.com). + +Meta-note : the triple pound signs are here to denote headlines, double paragraphs, single notes. +`#=>` represents the output of a command. + +```perl +# Single line comment start with a pound + +#`( + Multiline comments use #` and a quoting construct. (), [], {}, 「」, etc, will work. +) + +### Variables + +# In Perl 6, you declare a lexical variable using `my` +a +# Perl 6 has 4 variable types : + +## * Scalars. They represent a single value. They start with a `$` + +my $str = 'String'; +my $str2 = "String"; # double quotes allow for interpolation + +# variable names can contain but not end with simple quotes and dashes, and can contain (and end with) underscores : +# my $weird'variable-name_ = 5; # works ! + +my $bool = True; # `True` and `False` are Perl 6's boolean +my $inverse = !$bool; # You can invert a bool with the prefix `!` operator +my $forced-bool = so $str; # And you can use the prefix `so` operator which turns its operand into a Bool + +## * Arrays. They represent multiple values. Their name start with `@`. + +my @array = 1, 2, 3; +my @array = 'a', 'b', 'c'; +# equivalent to : +my @array = <a b c>; # array of words, delimited by space. similar to perl5's qw, or Ruby's %w + +say @array[2]; # Array indices start at 0 -- This is the third element + +say "Interpolate an array using [] : @array[]"; #=> Interpolate an array using [] : a b c + +## * Hashes. Key-Value Pairs. +# Hashes are actually arrays of Pairs (`Key => Value`), +# except they get "flattened", removing duplicated keys. +my %hash = 1 => 2, + 3 => 4; +my %hash = autoquoted => "key", # keys *can* get auto-quoted + "some other" => "value", # trailing commas are okay + ; +my %hash = <key1 value1 key2 value2>; # you can also create a hash from an even-numbered array +my %hash = key1 => 'value1', key2 => 'value2'; # same as this + +# You can also use the "colon pair" syntax: (especially handy for named parameters that you'll see later) +my %hash = :w(1), # equivalent to `w => 1` + # this is useful for the `True` shortcut: + :truey, # equivalent to `:truey(True)`, or `truey => True` + # and for the `False` one: + :!falsey, # equivalent to `:falsey(False)`, or `falsey => False` + ; + +say %hash{'key1'}; # You can use {} to get the value from a key +say %hash<key2>; # if it's a string, you can actually use <> + +## * Subs (subroutines, or functions in most other languages). Stored in variable, they use `&` +sub say-hello { say "Hello, world" } + +sub say-hello-to(Str $name) { # you can provide the type of an argument + # and it'll be checked at compile-time + + say "Hello, $name !"; +} + +# since you can omit parenthesis to call a function with no arguments, +# you need "&" in the name to capture `say-hello` +my &s = &say-hello; +my &other-s = sub { say "anonymous function !" } + +# A sub can have a "slurpy" parameter, or "doesn't-matter-how-many" +sub as-many($head, *@rest) { # the `*@` slurpy will basically "take everything else". + # Note: you can have parameters *before* (like here) a slurpy one, + # but not *after*. + say @rest.join(' / ') ~ " !"; +} +say as-many('Happy', 'Happy', 'Birthday'); #=> Happy / Birthday ! + # Note that the splat did not consume the parameter before. + +## You can call a function with an array using the "argument list flattening" operator `|` +# (it's not actually the only feature of the operator, but it's one of them) +sub concat3($a, $b, $c) { + say "$a, $b, $c"; +} +concat3(|@array); #=> a, b, c + # `@array` got "flattened" as a part of the argument list + +## It can also have optional arguments: +sub with-optional($arg?) { # the "?" marks the argument optional + say "I might return `(Any)` if I don't have an argument passed, or I'll return my argument"; + $arg; +} +with-optional; # returns Any +with-optional(); # returns Any +with-optional(1); # returns 1 + +## You can also give them a default value when they're not passed: +sub hello-to($name = "World") { + say "Hello, $name !"; +} +hello-to; #=> Hello, World ! +hello-to(); #=> Hello, World ! +hello-to('You'); #=> Hello, You ! + +## You can also, by using a syntax akin to the one of hashes (yay unification !), +## pass *named* arguments to a `sub`. +sub with-named($normal-arg, :$named) { + say $normal-arg + $named; +} +with-named(1, named => 6); #=> 7 +# There's one gotcha to be aware of, here: +# If you quote your key, Perl 6 won't be able to see it at compile time, +# and you'll have a single Pair object as a positional paramater. + +with-named(2, :named(5)); #=> 7 +with-named(3, :4named); #=> 7 + # (special colon pair syntax for numbers, mainly useful for `:2nd` etc) + +with-named(3); # warns, because we tried to use the undefined $named in a `+`: + # by default, named arguments are *optional* + +# To make a named argument mandatory, you can use `?`'s inverse, `!` +sub with-mandatory-named(:$str!) { + say "$named !"; +} +with-mandatory-named(str => "My String"); #=> My String ! +with-mandatory-named; # run time error: "Required named parameter not passed" +with-mandatory-named(3); # run time error: "Too many positional parameters passed" + +## If a sub takes a named boolean argument ... +sub takes-a-bool($name, :$bool) { + say "$name takes $bool"; +} +# ... you can use the same "short boolean" hash syntax: +takes-a-bool('config', :bool); # config takes True +takes-a-bool('config', :!bool); # config takes False +# or you can use the "adverb" form: +takes-a-bool('config'):bool; #=> config takes True +takes-a-bool('config'):!bool; #=> config takes False +# You'll learn to love (or maybe hate, eh) that syntax later. + + +## You can also provide your named arguments with defaults: +sub named-def(:$def = 5) { + say $def; +} +named-def; #=> 5 +named-def(:10def); #=> 10 +named-def(def => 15); #=> 15 + +# -- Note: we're going to learn *more* on subs really soon, +# but we need to grasp a few more things to understand their real power. Ready? + +### Containers +# In Perl 6, values are actually stored in "containers". +# The assignment operator asks the container on the left to store the value on its right. +# When passed around, containers are marked as immutable. Which means that, in a function, +# you'll get an error if you try to mutate one of your arguments. +# If you really need to, you can ask for a mutable container using `is rw` : +sub mutate($n is rw) { + $n++; + say "\$n is now $n !"; +} + +# If what you want is a copy instead, use `is copy`. + +# A sub itself returns a container, which means it can be marked as rw : +my $x = 42; +sub mod() is rw { $x } +mod() = 52; # in this case, the parentheses are mandatory (else Perl 6 thinks it's a "term") +say $x; #=> 52 + + +### Control Flow Structures + +# You don't need to put parenthesis around the condition, +# but that also means you always have to use brackets (`{ }`) for their body : + +## Conditionals + +# - `if` +# Before talking about `if`, we need to know which values are "Truthy" (represent True), +# and which are "Falsey" (or "Falsy") -- meaning they represent False. +# Only these values are Falsey: (), 0, "0", Nil, A type, and of course False itself. +# Every other value is Truthy. +if True { + say "It's true !"; +} + +unless False { + say "It's not false !"; +} + +# You can also use their postfix versions, with the keyword after: +say "Quite truthy" if True; + +# if (true) say; # This doesn't work ! + +# - Ternary conditional, "?? !!" (like `x ? y : z` in some other languages) +my $a = $condition ?? $value-if-true !! $value-if-false; + +# - `given`-`when` looks like other languages `switch`, but it's much more powerful thanks to smart matching, +# and thanks to Perl 6's "topic variable", $_. +# This variable contains the default argument of a block, +# a loop's current iteration (unless explicitly named), etc. +# Given simply puts its argument into `$_` (like a block would do), +# and `when` uses it using the "smart matching" operator. +# Since other Perl 6 constructs use this variable (as said before, like `for`, blocks, etc), +# this means the powerful `when` is not only applicable along with a `given`, +# but instead anywhere a `$_` exists. +given "foo bar" { + when /foo/ { # you'll read about the smart-matching operator below -- just know `when` uses it + # this is equivalent to `if $_ ~~ /foo/` + say "Yay !"; + } + when $_.chars > 50 { # smart matching anything with True (`$a ~~ True`) is True, + # so you can also put "normal" conditionals. + say "Quite a long string !"; + } + default { # same as `when *` (using the Whatever Star) + say "Something else" + } +} + +## Looping constructs + +# - `loop` is an infinite loop if you don't pass it arguments, but can also be a c-style `for` : +loop { + say "This is an infinite loop !"; + last; # last breaks out of the loop, like the `break` keyword in other languages +} + +loop (my $i = 0; $i < 5; $i++) { + next if $i == 3; # `next` skips to the next iteration, like `continue` in other languages. + # Notice that you can also use postfix conditionals, loops, etc. + say "This is a C-style for loop !"; +} + +# - `for` - Passes through an array +for @array -> $variable { + say "I've found $variable !"; +} + +# As we saw with given, for's default "current iteration" variable is `$_`. +# That means you can use `when` in a `for` just like you were in a when. +for @array { + say "I've got $_"; + + .say; # This is also allowed. + # A dot call with no "topic" (receiver) is sent to `$_` by default + $_.say; # the above and this are equivalent. +} + +for @array { + next if $_ == 3; # you can skip to the next iteration (like `continue` in C-like languages) + redo if $_ == 4; # you can re-do the iteration, keeping the same topic variable (`$_`) + last if $_ == 5; # you can also break out of a loop (like `break` in C-like languages) +} + +# Note - the "lambda" `->` syntax isn't reserved to `for` : +if long-computation() -> $result { + say "The result is $result"; +} + +### Operators + +## Since Perl languages are very much operator-based languages +## Perl 6 operators are actually just funny-looking subroutines, in syntactic categories, +## like infix:<+> (addition) or prefix:<!> (bool not) + +## The categories are : +# - "prefix" : before (like `!` in `!True`). +# - "postfix" : after (like `++` in `$a++`). +# - "infix" : in between (like `*` in `4 * 3`). +# - "circumfix" : around (like `[`-`]` in `[1, 2]`). +# - "post-circumfix" : around, after another term (like `{`-`}` in `%hash{'key'}`) + +## The associativity and precedence list are explained below. + +# Alright, you're set to go ! + +## * Equality Checking + +# - `==` is numeric comparison +3 == 4; # False +3 != 4; # True + +# - `eq` is string comparison +'a' eq 'b'; +'a' ne 'b'; # not equal +'a' !eq 'b'; # same as above + +# - `eqv` is canonical equivalence (or "deep equality") +(1, 2) eqv (1, 3); + +# - `~~` is smart matching +# for a complete combinations list, use this table : http://perlcabal.org/syn/S03.html#Smart_matching +'a' ~~ /a/; # true if matches regexp +'key' ~~ %hash; # true if key exists in hash +$arg ~~ &bool-returning-function; # true if the function, passed `$arg` as an argument, returns True +1 ~~ Int; # "is of type" +1 ~~ True; # smart-matching against a boolean always returns that boolean (and will warn). + +# - `===` is value identity and uses `.WHICH` on the objects to compare them +# - `=:=` is container identity and uses `VAR()` on the objects to compare them + +# You also, of course, have `<`, `<=`, `>`, `>=`. +# Their string equivalent are also avaiable : `lt`, `le`, `gt`, `ge`. +3 > 4; + +## * Range constructors +3 .. 7; # 3 to 7, both included +# `^` on either side them exclusive on that side : +3 ^..^ 7; # 3 to 7, not included (basically `4 .. 6`) +# this also works as a shortcut for `0..^N` +^10; # means 0..^10 + +# This also allows us to demonstrate that Perl 6 has lazy arrays, using the Whatever Star : +my @array = 1..*; # 1 to Infinite ! +say @array[^10]; # you can pass arrays as subscripts and it'll return an array of results + # this will print "1 2 3 4 5 6 7 8 9 10" (and not run out of memory !) +# Note : when reading an infinite list, Perl 6 will "reify" the elements it needs, then keep them in memory +# They won't be calculated more than once. + +# Warning, though: if you try this example in the REPL and juste put `1..*`, +# Perl 6 will be forced to try and evaluate the whole array (to print it), +# so you'll end with an infinite loop. + +## * And, Or +3 && 4; # 4, which is Truthy. Calls `.Bool` on `4` and gets `True`. +0 || False; # False. Calls `.Bool` on `0` + +## * Short-circuit (and tight) versions of the above +$a && $b && $c; # returns the first argument that evaluates to False, or the last argument +$a || $b; + +# And because you're going to want them, you also have composed assignment operators: +$a *= 2; # multiply and assignment +$b %%= 5; # divisible by and assignment +$c .= say; # method call and assignment + +### More on subs ! +# As we said before, Perl 6 has *really* powerful subs. +# We're going to see a few more key concepts that make them better than in any other language :-). + +## Unpacking ! It's the ability to "extract" arrays and keys. It'll work in `my`s and parameters. +my ($a, $b) = 1, 2; +say $a; #=> 1 +my ($, $, $c) = 1, 2, 3; # keep the non-interesting anonymous +say $c; #=> 3 + +my ($head, *@tail) = 1, 2, 3; # Yes, it's the same as with "slurpy subs" +my (*@small) = 1; + +sub foo(@array [$fst, $snd]) { + say "My first is $fst, my second is $snd ! All in all, I'm @array[]."; + # (^ remember the `[]` to interpolate the array) +} +foo(@tail); #=> My first is 2, my second is 3 ! All in all, I'm 2 3 + + +# If you're not using the array itself, you can also keep it anonymous, much like a scalar: +sub first-of-array(@ [$fst]) { $fst } +first-of-array(@small); #=> 1 +first-of-array(@tail); # errors with "Too many positional parameters passed" (the array is too big) + +# You can also use a slurp ... +sub slurp-in-array(@ [$fst, *@rest]) { # you could decide to keep `*@rest` anonymous + say $fst + @rest.elems; +} +slurp-in-array(@tail); #=> 3 + +# You could even extract on a slurpy (but it's pretty useless ;-).) +sub fst(*@ [$fst]) { # or simply : `sub fst($fst) { ... }` + say $fst; +} +fst(1); #=> 1 +fst(1, 2); # errors with "Too many positional parameters passed" + +# You can also destructure hashes (and classes, which you'll learn about later !) +# The syntax is basically `%hash-name (:key($variable-to-store-value-in))`. +# The hash can stay anonymous if you only need the values you extracted. +sub key-of(% (:value($val), :qua($qua))) { + say "Got val $val, $qua times."; +} + +# Then call it with a hash: (you need to keep the brackets for it to be a hash) +key-of({value => 1}); +#key-of(%hash); # the same (for an equivalent `%hash`) + +## The last expression of a sub is returned automatically (though you may use the `return` keyword, of course): +sub next-index($n) { + $n + 1; +} +my $new-n = next-index(3); # $new-n is now 4 + +# This is true for everything, except for the looping constructs (due to performance reasons): +# there's no purpose in building a list if we're just going to discard all the results. +# If you still want to build one, you can use the `do` prefix: (or the `gather` prefix, which we'll see later) +sub list-of($n) { + do for ^$n { # note the use of the range-to prefix operator `^` (`0..^N`) + $_ # current loop iteration + } +} +my @list3 = list-of(3); #=> (0, 1, 2) + +## You can create a lambda with `-> {}` ("pointy block") or `{}` ("block") +my &lambda = -> $argument { "The argument passed to this lambda is $argument" } +# `-> {}` and `{}` are pretty much the same thing, except that the former can take arguments, +# and that the latter can be mistaken as a hash by the parser. + +# We can, for example, add 3 to each value of an array using map: +my @arrayplus3 = map({ $_ + 3 }, @array); # $_ is the implicit argument + +# a sub (`sub {}`) has different semantics than a block (`{}` or `-> {}`): +# a block doesn't have a "function context" (though it can have arguments), which means that if you +# return from it, you're going to return from the parent function, compare: +sub is-in(@array, $elem) { + # this will `return` out of the `is-in` sub + # once the condition evaluated to True, the loop won't be run anymore + map({ return True if $_ == $elem }, @array); +} +sub truthy-array(@array) { + # this will produce an array of `True` and `False`: + # (you can also say `anon sub` for "anonymous subroutine") + map(sub { if $_ { return True } else { return False } }, @array); + # ^ the `return` only returns from the anonymous `sub` +} + +# You can also use the "whatever star" to create an anonymous function +# (it'll stop at the furthest operator in the current expression) +my @arrayplus3 = map(*+3, @array); # `*+3` is the same as `{ $_ + 3 }` +my @arrayplus3 = map(*+*+3, @array); # also works. Same as `-> $a, $b { $a + $b + 3 }` +say (*/2)(4); #=> 2 + # Immediatly execute the function Whatever created. +say ((*+3)/5)(5); #=> 1.6 + # works even in parens ! + +# but if you need to have more than one argument (`$_`) in a block (without wanting to resort to `-> {}`), +# you can also use the implicit argument syntax, `$^` : +map({ $^a + $^b + 3 }, @array); # same as the above + +# Note : those are sorted lexicographically. `{ $^b / $^a }` is like `-> $a, $b { $b / $a }` + +## Multiple Dispatch +# Perl 6 can decide which variant of a `sub` to call based on the type of the arguments, +# or on arbitrary preconditions, like with a type or a `where`: + +# with types +multi sub sayit(Int $n) { # note the `multi` keyword here + say "Number: $n"; +} +multi sayit(Str $s) } # the `sub` is the default + say "String: $s"; +} +sayit("foo"); # prints "String: foo" +sayit(True); # fails at *compile time* with "calling 'sayit' will never work with arguments of types ..." + +# with arbitrary precondition: +multi is-big(Int $n where * > 50) { "Yes !" } # using a closure +multi is-big(Int $ where 10..50) { "Quite." } # this uses smart-matching (could use a regexp, etc) +multi is-big(Int $) { "No" } + +# you can also name these checks, by creating "subsets": +subset Even of Int where * %% 2; + +multi odd-or-even(Even) { "Even" } # the main case using the type. We don't name the argument +multi odd-or-even($) { "Odd" } # "else" + +# You can even dispatch based on a positional's argument presence ! +multi with-or-without-you(:$with!) { # make it mandatory to be able to dispatch against it + say "I can live ! Actually, I can't."; +} +multi with-or-without-you { + say "Definitely can't live."; +} +# This is very, very useful for many purposes, like `MAIN` subs (covered later), +# and even the language itself is using it in several places. +# `is`, for example, is actually a `multi sub` named `trait_mod:<is>`, and it works off that. +# `is rw`, for example, is a dispatch to a function with this signature: +# sub trait_mod:<is>(Routine $r, :$rw!) {} +# (commented because running this would probably lead to some very surprising side-effects !) + + +### Scoping +# In Perl 6, contrarily to many scripting languages (Python, Ruby, PHP, for example), +# you are to declare your variables before using them. You already saw it, with `my`. +# (there are other declarator keywords, like `our`, `has` and `state`, but we'll talk about them later) +# This is called "lexical scoping", where in inner blocks, you can access variables from outer blocks. +my $foo = 'Foo'; +sub foo { + my $bar = 'Bar'; + sub bar { + say "$foo $bar"; + } + &bar; # return the function +} +foo()(); #=> 'Foo Bar' + +# As you can see, `$foo` and `$bar` were captured. +# But if we were to try and use `$bar` outside of `foo`, the variable would be undefined. +# (and you'd get a compile time error) + +# Perl 6 has another kind of scope : dynamic scope. +# They use the twigil (composed sigil) `*` to mark dynamically-scoped variables: +my $*a = 1; +# Dyamically-scoped variables depend on the current call stack, instead of the current block stack. +sub foo { + my $*foo = 1; + bar(); # call `bar` in-place +} +sub bar { + say $*foo; # Perl 6 will look into the call stack instead, and find `foo`'s `$*a`, + # even though the blocks aren't nested (they're call-nested). + #=> 1 +} + +### Object Model + +## Perl 6 has a quite comprehensive object model +## You declare a class with the keyword `class`, fields with `has`, methods with `method`. +## In Perl 6, every field is private, and named `$!attr`, but if you declare it with `$.`, +## you get a public (immutable) accessor along with it. + +# (Perl 6's object model ("SixModel") is very flexible, and allows you to dynamically add methods, +# change semantics, etc -- This will not be covered here, and you should refer to the Synopsis) + +class A { + has $.field; # `$.field` is immutable. Use `$!field` from inside the class to modify it. + has $.other-field is rw; # You can, however, mark a public field as being read/write. + has Int $!private-field = 10; + + method get-value { + $.field + $!private-field + $n; + } + + method set-value($n) { + # $.field = $n; # As stated before, you can't use the `$.` immutable version. + $!field = $n; # This works, because `$!` is always mutable. + + $.other-field = 5; # This works, because `$.other-field` was declared `rw` (mutable). + } + + method !private-method { + say "This method is private to the class !"; + } +}; + +# Create a new instance of A with $.field set to 5 : +# note : you can't set private-field from here (more later on) +my $a = A.new(field => 5); +$a.get-value; #=> 18 +#$a.field = 5; # This fails, because the `has $.field` is immutable +$a.other-field = 10; # This, however, works, because the public field is mutable (`rw`). + +## Perl 6 also has inheritance (along with multiple inheritance ... Considered a misfeature by many) + +class A { + has $.val; + + submethod not-inherited { + say "This method won't be available on B."; + say "This is most useful for BUILD, which we'll see later"; + } + + method bar { $.val * 5 } +} +class B is A { # inheritance uses `is` + method foo { + say $.val; + } + + method bar { $.val * 10 } # this shadows A's `bar` +} + +my B $b .= new(val => 5); # When you use `my T $var`, `$var` starts off with `T` itself in it, + # so you can call `new` on it. + # (`.=` is just the compound operator composed of the dot-call and of the assignment operator + # `$a .= b` is the same as `$a = $a.b`) + # Also note that `BUILD` (the method called inside `new`) will set parent properties too, + # so you can pass `val => 5` +# $b.not-inherited; # This won't work, for reasons explained above +$b.foo; # prints 5 +$b.bar; #=> 50, since it calls B's `bar` + +## Roles are supported too (also called Mixins in other languages) +role PrintableVal { + has $!counter = 0; + method print { + say $.val; + } +} + +# you "use" a mixin with "does" : +class Item does PrintableVal { + has $.val; + + # When `does`-ed, a `role` literally "mixes in" the class : + # the methods and fields are put together, which means a class can access + # the private fields/methods of its roles (but not the inverse !) : + method access { + say $!counter++; + } + + # However, this : + # method print {} + # is an error, since the compiler wouldn't know which `print` to use : + # contrarily to inheritance, methods mixed in can't be shadowed - they're put at the same "level" + + # NOTE: You can use a role as a class (with `is ROLE`). In this case, methods will be shadowed, + # since the compiler will consider `ROLE` to be a class +} + +### Exceptions +# Exceptions are built on top of classes, usually in the package `X` (like `X::IO`). +# Unlike many other languages, in Perl 6, you put the `CATCH` block *within* the block to `try`. +# By default, a `try` has a `CATCH` block that catches any exception (`CATCH { default {} }`). +# You can redefine it using `when`s (and `default`) to handle the exceptions you want: +try { + open 'foo'; + CATCH { + when X::AdHoc { say "unable to open file !" } + # any other exception will be re-raised, since we don't have a `default` + } +} + +# You can throw an exception using `die`: +die X::AdHoc.new(payload => 'Error !'); +# TODO warn +# TODO fail +# TODO CONTROL + +### Packages +# Packages are a way to reuse code. Packages are like "namespaces", and any element of the six model +# (`module`, `role`, `class`, `grammar`, `subset` and `enum`) are actually packages. +# (you can say that packages are the lowest common denomitor between them) +# Packages play a big part in a language, as Perl is well-known for CPAN, +# the Comprehensive Perl Archive Network. +# You usually don't use packages directly : you use `class Package::Name::Here;`, or if you +# only want to export variables/subs, you can use `module`: +module Hello::World { # bracketed form + # if `Hello` doesn't exist yet, it'll just be created as an "empty package stub" + # that can be redeclared as something else later. + # declarations here +} +module Parse::Text; # file-scoped form +grammar Parse::Text::Grammar { # A grammar is a fine package, which you could `use` +} + +# NOTE for Perl 5 users: even though the `package` keyword exists, +# the braceless form is invalid (to catch a "perl5ism"). This will error out: +# package Foo; # because Perl 6 will think the entire file is Perl 5 +# Just use `module` or the brace version of `package`. + +# You can use a module (bring its declarations into scope) with `use` +use JSON::Tiny; # if you installed Rakudo* or Panda, you'll have this module +say from-json('[1]').perl; #=> [1] + +# As said before, any part of the six model is also a package. +# Since `JSON::Tiny` uses (its own) `JSON::Tiny::Actions` class, you can use it: +my $actions = JSON::Tiny::Actions.new; + +# We'll see how to export variables and subs in the next part: + +### Declarators +# In Perl 6, you get different behaviors based on how you declare a variable. +# You've already seen `my` and `has`, we'll now explore the others. + +## * `our` (happens at `INIT` time -- see "Phasers" below) +# Along with `my`, there are several others declarators you can use. +# The first one you'll want for the previous part is `our`. +# (All packagish things (`class`, `role`, etc) are `our` by default) +# it's like `my`, but it also creates a package variable: +module Foo::Bar { + our $n = 1; # note: you can't put a type constraint on an `our` variable + our sub inc { + our sub available { # if you try to make scoped `sub`s `our` ... Better know what you're doing (Don't !). + say "Don't do that. Seriously. You'd get burned."; + } + my sub unavailable { # `my sub` is the default + say "Can't access me from outside, I'm my !"; + } + } + + say ++$n; # lexically-scoped variables are still available +} +say $Foo::Bar::n; #=> 1 +Foo::Bar::inc; #=> 2 +Foo::Bar::inc; #=> 3 + +## * `constant` (happens at `BEGIN` time) +# You can use the `constant` keyword to declare a compile-time variable/symbol: +constant Pi = 3.14; +constant $var = 1; + +# And if you're wondering, yes, it can also contain infinite lists. +constant why-not = 5, 15 ... *; +say why-not[^5]; #=> 5 15 25 35 45 + +## * `state` (happens at run time, but only once) +# State variables are only executed one time +# (they exist in other langages such as C as `static`) +sub fixed-rand { + state $val = rand; + say $rand; +} +fixed-rand for ^10; # will print the same number 10 times + +# Note, however, that they exist separately in different enclosing contexts. +# If you declare a function with a `state` within a loop, it'll re-create the variable +# for each iteration of loop. See: +for ^5 -> $a { + sub foo { + state $val = rand; # This will be a different value for every value of `$a` + } + for ^5 -> $b { + say foo; # This will print the same value 5 times, but only 5. Next iteration will re-run `rand` + } +} + + + +### Phasers +# Phasers in Perl 6 are blocks that happen at determined points of time in your program +# When the program is compiled, when a for loop runs, when you leave a block, when +# an exception gets thrown ... (`CATCH` is actually a phaser !) +# Some of them can be used for their return values, some of them can't +# (those that can have a "[*]" in the beginning of their explanation text). +# Let's have a look ! + +## * Compile-time phasers +BEGIN { say "[*] Runs at compile time, as soon as possible, only once" } +CHECK { say "[*] Runs at compile time, instead as late as possible, only once" } + +## * Run-time phasers +INIT { say "[*] Runs at run time, as soon as possible, only once" } +END { say "Runs at run time, as late as possible, only once" } + +## * Block phasers +ENTER { say "[*] Runs everytime you enter a block, repeats on loop blocks" } +LEAVE { say "Runs everytime you leave a block, even when an exception happened. Repeats on loop blocks." } + +PRE { say "Asserts a precondition at every block entry, before ENTER (especially useful for loops)" } +POST { say "Asserts a postcondition at every block exit, after LEAVE (especially useful for loops)" } + +## * Block/exceptions phasers +sub { + KEEP { say "Runs when you exit a block successfully (without throwing an exception)" } + UNDO { say "Runs when you exit a block unsuccessfully (by throwing an exception)" } +} + +## * Loop phasers +for ^5 { + FIRST { say "[*] The first time the loop is run, before ENTER" } + NEXT { say "At loop continuation time, before LEAVE" } + LAST { say "At loop termination time, after LEAVE" } +} + +## * Role/class phasers +COMPOSE { "When a role is composed into a class. /!\ NOT YET IMPLEMENTED" } + +# They allow for cute trick or clever code ...: +say "This code took " ~ (time - CHECK time) ~ "s to run"; + +# ... or clever organization: +sub do-db-stuff { + ENTER $db.start-transaction; # create a new transaction everytime we enter the sub + KEEP $db.commit; # commit the transaction if all went well + UNDO $db.rollback; # or rollback if all hell broke loose +} + +### Statement prefixes +# Those act a bit like phasers: they affect the behavior of the following code. +# Though, they run in-line with the executable code, so they're in lowercase. +# (`try` and `start` are theoretically in that list, but explained somewhere else) +# Note: all of these (except start) don't need explicit brackets (`{` and `}`) for their block. + +# - `do` (that you already saw) - runs a block or a statement as a term +# You can't normally use a statement as a value (or "term"): +# +# my $value = if True { 1 } # `if` is a statement - parse error +# +# This works: +my $a = do if True { 5 } # with `do`, `if` is now a term. + +# - `once` - Makes sure a piece of code only runs once +for ^5 { once say 1 }; #=> 1 + # Only prints ... once. +# Like `state`, they're cloned per-scope +for ^5 { sub { once say 1 }() } #=> 1 1 1 1 1 + # Prints once per lexical scope + +# - `gather` - Co-routine thread +# Gather allows you to `take` several values in an array, +# much like `do`, but allows you to take any expression. +say gather for ^5 { + take $_ * 3 - 1; + take $_ * 3 + 1; +} #=> -1 1 2 4 5 7 8 10 11 13 +say join ',', gather if False { + take 1; + take 2; + take 3; +} # Doesn't print anything. + +# - `eager` - Evaluate statement eagerly (forces eager context) +# Don't try this at home: +# +# eager 1..*; # this will probably hang for a while (and might crash ...). +# +# But consider: +constant thrice = gather for ^3 { say take $_ }; # Doesn't print anything +# versus: +constant thrice = eager gather for ^3 { say take $_ }; #=> 0 1 2 3 4 + +# - `lazy` - Defer actual evaluation until value is fetched (forces lazy context) +# Not yet implemented !! + +# - `sink` - An `eager` that discards the results (forces sink context) +constant nilthingie = sink for ^3 { .say } #=> 0 1 2 +say nilthingie.perl; #=> Nil + +# - `quietly` - Supresses warnings +# Not yet implemented ! + +# - `contend` - Attempts side effects under STM +# Not yet implemented ! + +### More operators thingies ! + +## Everybody loves operators ! Let's get more of them + +## The precedence list can be found here : http://perlcabal.org/syn/S03.html#Operator_precedence +## But first, we need a little explanation about associativity : + +# * Binary operators: +$a ! $b ! $c; # with a left-associative `!`, this is `($a ! $b) ! $c` +$a ! $b ! $c; # with a right-associative `!`, this is `$a ! ($b ! $c)` +$a ! $b ! $c; # with a non-associative `!`, this is illegal +$a ! $b ! $c; # with a chain-associative `!`, this is `($a ! $b) and ($b ! $c)` +$a ! $b ! $c; # with a list-associative `!`, this is `infix:<>` + +# * Unary operators: +!$a! # with left-associative `!`, this is `(!$a)!` +!$a! # with right-associative `!`, this is `!($a!)` +!$a! # with non-associative `!`, this is illegal + +## Create your own operators ! +# Okay, you've been reading all of that, so I guess I should try to show you something exciting. +# I'll tell you a little secret (actually not): +# In Perl 6, all operators are actually just funny-looking subroutines. + +# You can declare an operator just like you declare a sub: +sub prefix:<win>($winner) { # refer to the operator categories + # (yes, it's the "words operator" `<>`) + say "$winner Won !"; +} +win "The King"; #=> The King Won ! + # (prefix is before) + +# you can still call the sub with its "full name" +say prefix:<!>(True); #=> False + +sub postfix:<!>(Int $n) { + [*] 2..$n; # using the reduce meta-operator ... See below ;-) ! +} +say 5!; #=> 120 + # Postfix operators (after) have to come *directly* after the term. + # No whitespace. You can use parentheses to disambiguate, i.e. `(5!)!` + + +sub infix:<times>(Int $n, Block $r) { # infix in the middle + for ^$n { + $r(); # You need the explicit parentheses to call the function in `$r`, + # else you'd be referring at the variable itself, kind of like with `&r`. + } +} +3 times -> { say "hello" }; #=> hello + #=> hello + #=> hello + # You're very recommended to put spaces + # around your infix operator calls. + +# For circumfix and post-circumfix ones +sub circumfix:<[ ]>(Int $n) { + $n ** $n +} +say [5]; #=> 3125 + # circumfix is around. Again, not whitespace. + +sub postcircumfix:<{ }>(Str $s, Int $idx) { # post-circumfix is "after a term, around something" + $s.substr($idx, 1); +} +say "abc"{1}; #=> b + # after the term `"abc"`, and around the index (1) + +# This really means a lot -- because everything in Perl 6 uses this. +# For example, to delete a key from a hash, you use the `:delete` adverb (named argument) +%h{$key}:delete; +# equivalent to: +postcircumfix:<{ }>(%h, $key, :delete); +# It's *all* using the same building blocks! Syntactic categories (prefix infix ...), +# named arguments (adverbs), ..., used to build the language are available to you. + +# (you are, obviously, recommended against making an operator out of *everything* -- +# with great power comes great responsibility) + +## Meta operators ! +# Oh boy, get ready. Get ready, because we're dwelving deep into the rabbit's hole, +# and you probably won't want to go back to other languages after reading that. +# (I'm guessing you don't want to already at that point). +# Meta-operators, as their name suggests, are *composed* operators. +# Basically, they're operators that apply another operator. + +## * Reduce meta-operator +# It's a prefix meta-operator that takes a binary functions and one or many lists. +# If it doesn't get passed any argument, it either return a "default value" for this operator +# (a value that'd be non-meaningful if contained in a list) or `Any` if there's none. +# Otherwise, it pops an element from the list(s) one at a time, and applies the binary function +# to the last result (or the list's first element) and the popped element. +# To sum a list, you could use the reduce meta-operator with `+`, i.e.: +say [+] 1, 2, 3; #=> 6 +# equivalent to `(1+2)+3` +say [*] 1..5; #=> 120 +# equivalent to `((((1*2)*3)*4)*5)`. + +# You can reduce with any operator, not just with mathematical ones. +# For example, you could reduce with `//` to get the first defined element of a list: +say [//] Nil, Any, False, 1, 5; #=> False + # (Falsey, but still defined) + + +# Default value examples: +say [*] (); #=> 1 +say [+] (); #=> 0 + # In both cases, they're results that, if they were contained in the lists, + # wouldn't have any impact on the final value (since N*1=N and N+0=N). +say [//]; #=> (Any) + # There's no "default value" for `//` + +# You can also call it with a function you made up, using double brackets: +sub add($a, $b) { $a + $b } +say [[&add]] 1, 2, 3; #=> 6 + +## * Zip meta-operator +# This one is an infix meta-operator than also can be used as a "normal" operator. +# It takes an optional binary function (by default, it just creates a pair), +# and will pop one value off of each array and call its binary function on these +# until it runs out of elements. It runs the an array with all these new elements. +(1, 2) Z (3, 4); # ((1, 3), (2, 4)), since by default, the function makes an array +1..3 Z+ 4..6; # (5, 7, 9), using the custom infix:<+> function + +# Since `Z` is list-associative (see the list above), +# you can use it on more than one list +(True, False) Z|| (False, False) Z|| (False, False); # (True, False) + +# And, as it turns out, you can also use the reduce meta-operator with it: +[Z||] (True, False), (False, False), (False, False); # (True, False) + + +## And to end the operator list: + +## * Sequence operator +# The sequence operator is one of Perl 6's most powerful features: +# it's composed of first, on the left, the list you want Perl 6 to deduce from (and might include a closure), +# and on the right, a value or the predicate for when to stop, or even Whatever for a lazy infinite list. +my @list = 1, 2, 3 ... 10; # basic deducing +#my @list = 1, 3, 6 ... 10; # this throws you into an infinite loop, because Perl 6 can't figure out the end +my @list = 1, 2, 3 ...^ 10; # as with ranges, you can exclude the last element (when the predicate matches) +my @list = 1, 3, 9 ... * > 30; # you can use a predicate (with the Whatever Star, here) +my @list = 1, 3, 9 ... { $_ > 30 }; # (equivalent to the above) +my @fib = 1, 1, *+* ... *; # lazy infinite list of prime numbers, computed using a closure ! +my @fib = 1, 1, -> $a, $b { $a + $b } ... *; # (equivalent to the above) +say @fib[^10]; #=> 1 1 2 3 5 8 13 21 34 55 + # (using a range as the index) +# Note : as for ranges, once reified, elements aren't re-calculated. +# That's why `@primes[^100]` will take a long time the first time you print it, then be instant + + +## * Sort comparison +# They return one value of the `Order` enum : `Less`, `Same` and `More` (which numerify to -1, 0 or +1). +1 <=> 4; # sort comparison for numerics +'a' leg 'b'; # sort comparison for string +$obj eqv $obj2; # sort comparison using eqv semantics + +## * Generic ordering +3 before 4; # True +'b' after 'a'; # True + +## * Short-circuit default operator +# Like `or` and `||`, but instead returns the first *defined* value : +say Any // Nil // 0 // 5; #=> 5 + +## * Short-circuit exclusive or (XOR) +# Returns `True` if one (and only one) of its arguments is true +say True ^^ False; #=> True + +## * Flip Flop +# The flip flop operators (`ff` and `fff`, equivalent to Perl 5/Ruby's `..` and `...`). +# are operators that take two predicates to test: +# They are `False` until their left side returns `True`, then are `True` until their right side returns `True`. +# Like for ranges, you can exclude the iteration when it became `True`/`False` by using `^` on either side. +# Let's start with an example : +for <well met young hero we shall meet later> { + # by default, `ff`/`fff` smart-match (`~~`) against `$_`: + if 'met' ^ff 'meet' { # won't enter the if for "met" (explained in details below). + .say + } + + if rand == 0 ff rand == 1 { # compare variables other than `$_` + say "This ... probably will never run ..."; + } +} +# This will print "young hero we shall meet" (excluding "met"): +# the flip-flop will start returning `True` when it first encounters "met" +# (but will still return `False` for "met" itself, due to the leading `^` on `ff`), +# until it sees "meet", which is when it'll start returning `False`. + +# The difference between `ff` (awk-style) and `fff` (sed-style) is that +# `ff` will test its right side just as its left side changes to `True`, +# and can get back to `False` right away (*except* it'll be `True` for the iteration that matched) +# while `fff` will wait for the next iteration to try its right side, once its left side changed: +.say if 'B' ff 'B' for <A B C B A>; #=> B B + # because the right-hand-side was tested directly (and returned `True`). + # "B"s are still printed since it matched that time + # (it just went back to `False` right away) +.say if 'B' fff 'B' for <A B C B A>; #=> B C B + # because the right-hand-side wasn't tested until `$_` became "C" + # (and thus did not match directly). + +# A flip-flop can change state as many times as needed: +for <test start print this stop you stopped printing start printing again stop not anymore> { + .say if $_ eq 'start' ^ff^ $_ eq 'stop'; # exclude both "start" and "stop", + #=> "print this printing again" +} + +# you might also use a Whatever Star, +# which is equivalent to `True` for the left side or `False` for the right: +for (1, 3, 60, 3, 40, 60) { # Note: the parenthesis are superfluous here -- sometimes called "superstitious" + .say if $_ > 50 ff *; # Once the flip-flop reaches a number greater than 50, it'll never go back to `False` + #=> 60 3 40 60 +} + +# You can also use this property to create an `If` that'll not execute the first time : +for <a b c> { + .say if * ^ff *; # the flip-flop is `True` and never goes back to `False`, + # but the `^` makes it *not run* on the first iteration + #=> b c +} + + +### Regular Expressions +# I'm sure a lot of you have been waiting for this one. +# Well, now that you know a good deal of Perl 6 already, we can get started. +# First off, you'll have to forget about "PCRE regexps" (perl-compatible regexps). +# +# IMPORTANT: You may feel like you already know these because you know PCRE. You'd be wrong. +# Some things are the same (like `?`, `+`, and `*`), but sometimes the semantics change (`|`). +# Make sure you read carefully, because you might trip over a new behavior. +# +# Perl 6 has a looot of features related to RegExps. After all, Rakudo parses itself. +# We're first going to look at the syntax itself, then talk about grammars (PEG-like), +# differences between the `token`, `regex` and `rule` keywords, and some more. +# Side note: you still have access to PCRE regexps using the `:P5` modifier. +# (we won't be discussing this in this tutorial, however) +# +# In essence, Perl 6 natively implements PEG ("Parsing Expression Grammars"). +# The pecking order for ambiguous parses is determined by a multi-level tie-breaking test: +# - Longest token matching. `foo\s+` beats `foo` (by 2 or more positions) +# - Longest literal prefix. `food\w*` beats `foo\w*` (by 1) +# - Declaration from most-derived to less derived grammars (grammars are actually classes) +# - Earliest declaration wins +say so 'a' ~~ /a/; #=> True +say so 'a' ~~ / a /; # More readable with some spaces! + +# In all our examples, we're going to use the smart-matching operator against a regexp. +# We're converting the result using `so`, but in fact, it's returning a `Match` object. +# They know how to respond to list indexing, hash indexing (and return the matched string). +# The results of the match are also available as `$/` (implicitly lexically-scoped). +# You can also use the capture variables (`$0`, `$1`, ... - starting at 0, not 1 !). +# +# You can also note that `~~` does not perform start/end checking +# (meaning the regexp can be matched with just one char of the string), +# we're going to explain later how you can do it. + +# In Perl 6, you can have any alphanumeric as a literal, everything else has to be escaped, +# using a backslash or quotes. +say so 'a|b' ~~ / a '|' b /; # `True`. Wouln't mean the same if `|` wasn't escaped +say so 'a|b' ~~ / a \| b /; # `True`. Another way to escape it. + +# The whitespace in a regexp is actually not significant, +# unless you use the `:s` (`:sigspace`, significant space) modifier. +say so 'a b c' ~~ / a b c /; # `False`. Space is not significant here +say so 'a b c' ~~ /:s a b c /; # `True`. We added the modifier `:s` here. + +# It is, however, important as for how modifiers (that you're gonna see just below) +# are applied ... + +## Quantifying - `?`, `+`, `*` and `**`. +# - `?` - 0 or 1 +so 'ac' ~~ / a b c /; # `False` +so 'ac' ~~ / a b? c /; # `True`, the "b" matched 0 times. +so 'abc' ~~ / a b? c /; # `True`, the "b" matched 1 time. + +# ... As you read just before, whitespace is important because it determines +# which part of the regexp is the target of the modifier: +so 'def' ~~ / a b c? /; # `False`. Only the `c` is optional +so 'def' ~~ / ab?c /; # `False`. Whitespace is not significant +so 'def' ~~ / 'abc'? /; # `True`. The whole "abc" group is optional. + +# Here (and below) the quantifier applies only to the `b` + +# - `+` - 1 or more +so 'ac' ~~ / a b+ c /; # `False`; `+` wants at least one matching +so 'abc' ~~ / a b+ c /; # `True`; one is enough +so 'abbbbc' ~~ / a b+ c /; # `True`, matched 4 "b"s + +# - `*` - 0 or more +so 'ac' ~~ / a b* c /; # `True`, they're all optional. +so 'abc' ~~ / a b* c /; # `True` +so 'abbbbc' ~~ / a b* c /; # `True` +so 'aec' ~~ / a b* c /; # `False`. "b"(s) are optional, but can't be something else. + +# - `**` - "Quantify It Yourself". +# If you squint hard enough, you might understand the why exponentation means quantity. +so 'abc' ~~ / a b ** 1 c /; # `True` (exactly one time) +so 'abc' ~~ / a b ** 1..3 c /; # `True` (one to three times) +so 'abbbc' ~~ / a b ** 1..3 c /; # `True` +so 'abbbbbbc' ~~ / a b ** 1..3 c /; # `False` (too much) +so 'abbbbbbc' ~~ / a b ** 3..* c /; # `True` (infinite ranges are okay) + +## Grouping and capturing +# Group: you can group parts of your regexp with `[]`. +# These groups are *not* captured (like PCRE's `(?:)`). +so 'abc' ~~ / a [ b ] c /; # `True`. The grouping does pretty much nothing +so 'fooABCABCbar' ~~ / foo [ A B C ] + bar /; # `True`. + # We match the "abc" 1 or more time. + # (the `+` was applied to the group) + +# But this does not go far enough, because we can't actually get back what we matched. +# Capture: We can actually *capture* the results of the regexp, using parentheses. +so 'fooABCABCbar' ~~ / foo ( A B C ) + bar /; # `True`. (we keep `so` here and use `$/` below) + +# So, starting with the grouping explanations. +# As we said before, our `Match` object is available as `$/`: +say $/; # Will print some weird stuff (we'll explain) (or "Nil" if nothing matched). + +# As we also said before, it has array indexing: +say $/[0]; #=> ｢ABC｣ ｢ABC｣ + # These weird brackets are `Match` objects. So here, we have an array of that. +say $0; # the same as above. + +# Our capture is `$0` because it's the first and only one capture in the regexp. +# You might be wondering why it's an array, and the answer is simple: +# Some capture (indexed using `$0`, `$/[0]` or a named one) will be an array +# IF it can have more than one element (so, with `*`, `+` and any `**`, but not with `?`). +# Let's use examples to see that: +so 'fooABCbar' ~~ / foo ( A B C )? bar /; # `True` +say $/[0]; #=> ｢ABC｣ +say $0.WHAT; #=> (Match) + # It can't be more than one, so it's only a single match object. +so 'foobar' ~~ / foo ( A B C )? bar /; #=> True +say $0.WHAT; #=> (Any) + # This capture did not match, so it's empty +so 'foobar' ~~ / foo ( A B C ) ** 0..1 bar /; # `True` +say $0.WHAT; #=> (Array) + # A specific quantifier will always capture an Array, + # may it be a range or a specific value (even 1). + +# If you're wondering how the captures are numbered, here's an explanation: +TODO use graphs from s05 + + +## Alternatives - the `or` of regexps +# WARNING: They are DIFFERENT from PCRE regexps. +so 'abc' ~~ / a [ b | y ] c /; # `True`. Either "b" or "y". +so 'ayc' ~~ / a [ b | y ] c /; # `True`. Obviously enough ... + +### Extra: the MAIN subroutime +# The `MAIN` subroutine is called when you run a Perl 6 file directly. +# It's very powerful, because Perl 6 actually parses the argument +# and pass them as such to the sub. It also handles named argument (`--foo`) +# and will even go as far as to autogenerate a `--help` +sub MAIN($name) { say "Hello, you !" } +# This produces: +# $ perl6 cli.pl +# Usage: +# t.pl <name> + +# And since it's a regular Perl 6 sub, you can haz multi-dispatch: +# (using a "Bool" for the named argument so that we get `--replace` instead of `--replace=`) +subset File of Str where *.IO.d; # convert to IO object, then check the file exists + +multi MAIN('add', $key, $value, Bool :$replace) { ... } +multi MAIN('remove', $key) { ... } +multi MAIN('import', File, Str :$as) { ... } # omitting parameter name +# This produces: +# $ perl 6 cli.pl +# Usage: +# t.pl [--replace] add <key> <value> +# t.pl remove <key> +# t.pl [--as=<Str>] import (File) +# As you can see, this is *very* powerful. It even went as far as to show inline the constants. +# (the type is only displayed if 1. there's no argument name 2. it's a named argument) +``` + +If you want to go further, you can: + - Read the [Perl 6 Advent Calendar](http://perl6advent.wordpress.com/). This is probably the greatest source of Perl 6 information, snippets and such. + - Come along on `#perl6` at `irc.freenode.net`. The folks here are always helpful. + - Check the [source of Perl 6's functions and classes](https://github.com/rakudo/rakudo/tree/nom/src/core). Rakudo is mainly written in Perl 6 (with a lot of NQP, "Not Quite Perl", a Perl 6 subset easier to implement and optimize). + - Read the [Synopses](perlcabal.org/syn). They explain it from an implementor point-of-view, but it's still very interesting. diff --git a/pt-br/markdown-pt.html.markdown b/pt-br/markdown-pt.html.markdown new file mode 100644 index 00000000..cac4a13e --- /dev/null +++ b/pt-br/markdown-pt.html.markdown @@ -0,0 +1,251 @@ +--- +language: markdown +contributors: + - ["Dan Turkel", "http://danturkel.com/"] +translators: + - ["Miguel Araújo", "https://github.com/miguelarauj1o"] +lang: pt-br +filename: learnmarkdown-pt.md +--- + +Markdown foi criado por John Gruber in 2004. Originado para ser fácil de ler e +escrever sintaxe que converte facilmente em HTML (hoje, suporta outros formatos também). + +Dê-me feedback tanto quanto você quiser! / Sinta-se livre para a garfar (fork) e +puxar o projeto (pull request) + +``` +<!-- Markdown é um superconjunto do HTML, de modo que qualquer arvquivo HTML é +um arquivo Markdown válido, isso significa que nós podemos usar elementos HTML +em Markdown, como o elemento de comentário, e eles não serão afetados pelo analisador +de remarcação. No entanto, se você criar um elemento HTML em seu arquivo Markdown, você +não pode usar sintaxe remarcação dentro desse conteúdo do elemento.--> + +<!--Markdown também varia de implementação de um analisador para uma próxima. +Este guia vai tentar esclarecer quando as características são universais, ou quando eles são +específico para um determinado parser --> + +<!-- Cabeçalhos --> +<!-- Você pode criar elementos HTML <h1> até <h6> facilmente antecedendo o texto +que deseja estar nesse elemento por um número de hashes (#) --> +# Isto é um cabeçalho <h1> +## Isto é um cabeçalho <h2> +### Isto é um cabeçalho <h3> +#### Isto é um cabeçalho <h4> +##### Isto é um cabeçalho <h5> +###### Isto é um cabeçalho <h6> + +<!-- Markdown também nos fornece duas maneiras alternativas de indicar h1 e h2 --> +Isto é um cabeçalho h1 +====================== + +Isto é um cabeçalho h2 +---------------------- + +<!-- Estilos de texto simples --> +<!-- O texto pode ser facilmente denominado como remarcação itálico, negrito ou tachado usando --> + +*Este texto está em itálico* +_E este também está._ + +**Este texto está em negrito** +__E este também está._ + +***Este texto está em negrito e itálico.*** +**_E este também está_** +*--Danouse! Este também__* + +<!-- Em GitHub Flavored Markdown, que é usado para processar arquivos Markdown +Github, nós também temos: --> + +~~Este texto é processado com tachado.~~ + +<!-- Os parágrafos estão uma ou várias linhas adjacentes de texto separadas por +uma ou múltiplas linhas em branco. --> + +Este é um parágrafo. Eu estou digitando em um parágrafo, não é legal? + +Agora, eu estou no parágrado 2. +... Ainda continuo no parágrafo 2! :) + +Eu estou no parágrafo três. + +<!-- Se você quiser inserir uma tag HTML <br />, você pode acabar com um parágrafo +com dois ou mais espaços e, em seguida, começar um novo parágrafo --> + +Termino com dois espaços (destacar-me para vê-los). + +Há um <br /> acima de mim! + +<!-- Bloco de citações são fáceis e feito com o caractere >. --> + +> Este é um bloco de citação. Você pode +> Enrolar manualmente suas linhas e colocar um `>` antes de cada linha ou você pode +> deixar suas linhas ficarem muito longas e enrolar por conta própria. Não faz diferença, +> desde que eles começam com um `>`. + +> Você também pode usar mais de um nível +>> De recuo? +> Como pura é isso? + +<!-- Listas --> +<!-- As listas não ordenadas podem ser feitas usando asteriscos, positivos ou hífens --> + +* Item +* Item +* Outro item + +ou + ++ Item ++ Item ++ Outro item + +ou + +- Item +- Item +- Um último item + +<!-- Listas ordenadas são feitas com um número seguido por um ponto --> + +1. Item um +2. Item dois +3. Tem três + +<!-- Você não tem poder para rotular os itens corretamente e a remarcação será ainda +tornar os números em ordem, mas isso pode não ser uma boa idéia --> + +1. Item um +1. Item dois +1. Item três +<!-- (Isto é processado da mesma forma que o exemplo acima) --> + +<!-- Você também pode usar subtítulos --> + +1. Item um +2. Item dois +3. Item três + * Sub-item + * Sub-item +4. Item quatro + +<!-- blocos de código --> +<!-- Você pode indicar um bloco de código (que utiliza o elemento <code>) pelo recuo +uma linha com quatro espaços ou uma guia --> + + Isto é código + É assim, sacou? + +<!-- Você pode também re-guia (ou adicionar mais quatro espaços adicionais) para o recuo +dentro do seu código --> + + my_array.each do |item| + puts item + end + +<!-- Código embutido pode ser criada usando o caractere de crase ` --> + +John não sabia nem o que o função 'goto()' fazia! + +<!-- Em Github Flavored Markdown, você pode usar uma sintaxe especial para o código --> + +\`\`\`ruby <!-- exceto remover essas barras invertidas quando você faz isso, apenas ``` +ruby! --> +def foobar + puts "Hello world!" +end +\`\`\` <!-- Aqui também, não barras invertidas, apenas ``` --> + +<-- O texto acima não requer recuo, mas o Github vai usar a sintaxe +destacando do idioma que você especificar após a ``` --> + +<!-- Regra Horizontal (<hr />) --> +<!-- Regras horizontais são facilmente adicionados com três ou mais asteriscos ou hífens, +com ou sem espaços. --> + +*** +--- +- - - +**************** + +<!-- Links --> +<!-- Uma das melhores coisas sobre a remarcação é o quão fácil é fazer ligações. Colocar +o texto a ser exibido entre parênteses rígidos [] seguido pela url em parênteses () --> + +[Click aqui!](http://test.com/) + +<!-- Você também pode adicionar um título link usando aspas dentro dos parênteses --> + +[Click aqui!](http://test.com/ "Link para Test.com") + +<!-- Caminhos relativos funcionam também. --> + +[Ir para música](/música/). + +<!-- Markdown também suporta ligações de estilo de referência --> + +[Clique neste link] [link1] para mais informações sobre isso! +[Além disso, verifique este link] [foobar] se você quiser. + +[link1]: http://test.com/ "Legal!" +[foobar]: http://foobar.biz/ "OK!" + +<!-- O título também pode estar entre aspas simples ou entre parênteses, ou omitido +inteiramente. As referências podem estar em qualquer lugar no documento e os IDs de referência +pode ser qualquer um, desde que eles são únicos. --> + +<!-- Existe também o "nomear implícita", que permite que você use o texto do link como o id --> + +[Este] [] é um link. + +[este]: http://thisisalink.com/ + +<!-- Mas não são usados normalmente--> + +<!-- Imagens --> +<!-- As imagens são feitas da mesma forma que as ligações, mas com um ponto de exclamação na frente! --> + + + +<!-- E estilo de referência funciona como esperado --> + +![Este é o pairar-texto.][Myimage] + +[myimage]: relative/urls/legal/image.jpg "se você precisa de um título, é aqui" + +<!-- Miscelânea --> +<!-- Auto-links --> + +<http://testwebsite.com/> é equivalente a +[http://testwebsite.com/](http://testwebsite.com/) + +<!-- Auto-links para e-mails --> + +<foo@bar.com> + +<!-- Escapando caracteres --> + +Quero digitar * Este texto entre asteriscos *, mas eu não quero que ele seja +em itálico, então eu faço o seguinte: \*Este texto entre asteriscos \*. + +<!-- Tabelas --> +<!-- Tabelas estão disponíveis apenas no Github Flavored Markdown e são ligeiramente +complicadas, mas se você realmente quer: --> + +| Col1 | Col2 | Col3 | +| :----------- | :------: | ------------: | +| esquerda-alin| Centrado | direita-alinh | +| blah | blah | blah | + +<!-- Ou, para os mesmos resultados --> + +Col 1 | Col2 | Col3 +:-- | :-: | --: +Ugh isso é tão feio | faça isto | parar + +<!-- O fim! --> + +``` +Para mais informações, confira o post oficial de John Gruber de sintaxe [aqui](http://daringfireball.net/projects/markdown/syntax) +e de Adam Pritchard grande cheatsheet [aqui](https://github.com/adam-p/markdown-here/wiki/Markdown-Cheatsheet). diff --git a/python.html.markdown b/python.html.markdown index aa077e57..9057dde2 100644 --- a/python.html.markdown +++ b/python.html.markdown @@ -45,9 +45,11 @@ to Python 2.x. Look for another tour of Python 3 soon! 2.0 # This is a float 11.0 / 4.0 # => 2.75 ahhh...much better -# Truncation or Integer division +# Result of integer division truncated down both for positive and negative. 5 // 3 # => 1 5.0 // 3.0 # => 1.0 # works on floats too +-5 // 3 # => -2 +-5.0 // 3.0 # => -2.0 # Modulo operation 7 % 3 # => 1 @@ -334,6 +336,10 @@ try: raise IndexError("This is an index error") except IndexError as e: pass # Pass is just a no-op. Usually you would do recovery here. +except (TypeError, NameError): + pass # Multiple exceptions can be handled together, if required. +else: # Optional clause to the try/except block. Must follow all except blocks + print "All good!" # Runs only if the code in try raises no exceptions #################################################### @@ -435,7 +441,10 @@ class Human(object): # A class attribute. It is shared by all instances of this class species = "H. sapiens" - # Basic initializer + # Basic initializer, this is called when this class is instantiated. + # Note that the double leading and trailing underscores denote objects + # or attributes that are used by python but that live in user-controlled + # namespaces. You should not invent such names on your own. def __init__(self, name): # Assign the argument to the instance's name attribute self.name = name @@ -519,11 +528,15 @@ def double_numbers(iterable): # Instead of generating and returning all values at once it creates one in each # iteration. This means values bigger than 15 wont be processed in # double_numbers. -# Note range is a generator too. Creating a list 1-900000000 would take lot of -# time to be made -_range = range(1, 900000000) +# Note xrange is a generator that does the same thing range does. +# Creating a list 1-900000000 would take lot of time and space to be made. +# xrange creates an xrange generator object instead of creating the entire list like range does. +# We use a trailing underscore in variable names when we want to use a name that +# would normally collide with a python keyword +xrange_ = xrange(1, 900000000) + # will double all numbers until a result >=30 found -for i in double_numbers(_range): +for i in double_numbers(xrange_): print(i) if i >= 30: break @@ -536,10 +549,10 @@ for i in double_numbers(_range): from functools import wraps -def beg(_say): - @wraps(_say) +def beg(target_function): + @wraps(target_function) def wrapper(*args, **kwargs): - msg, say_please = _say(*args, **kwargs) + msg, say_please = target_function(*args, **kwargs) if say_please: return "{} {}".format(msg, "Please! I am poor :(") return msg diff --git a/python3.html.markdown b/python3.html.markdown index bc0c05bd..b494dc1e 100644 --- a/python3.html.markdown +++ b/python3.html.markdown @@ -38,9 +38,11 @@ Note: This article applies to Python 3 specifically. Check out the other tutoria # Except division which returns floats by default 35 / 5 # => 7.0 -# Truncation or Integer division +# Result of integer division truncated down both for positive and negative. 5 // 3 # => 1 -5.0 // 3.0 # => 1.0 +5.0 // 3.0 # => 1.0 # works on floats too +-5 // 3 # => -2 +-5.0 // 3.0 # => -2.0 # When you use a float, results are floats 3 * 2.0 # => 6.0 @@ -51,7 +53,6 @@ Note: This article applies to Python 3 specifically. Check out the other tutoria # Enforce precedence with parentheses (1 + 3) * 2 # => 8 - # Boolean values are primitives True False @@ -60,7 +61,6 @@ False not True # => False not False # => True - # Equality is == 1 == 1 # => True 2 == 1 # => False @@ -79,7 +79,6 @@ not False # => True 1 < 2 < 3 # => True 2 < 3 < 2 # => False - # Strings are created with " or ' "This is a string." 'This is also a string.' @@ -330,9 +329,12 @@ try: raise IndexError("This is an index error") except IndexError as e: pass # Pass is just a no-op. Usually you would do recovery here. +except (TypeError, NameError): + pass # Multiple exceptions can be handled together, if required. +else: # Optional clause to the try/except block. Must follow all except blocks + print("All good!") # Runs only if the code in try raises no exceptions - -# Python's offers a fundamental abstraction called the Iterable. +# Python offers a fundamental abstraction called the Iterable. # An iterable is an object that can be treated as a sequence. # The object returned the range function, is an iterable. @@ -340,7 +342,7 @@ filled_dict = {"one": 1, "two": 2, "three": 3} our_iterable = filled_dict.keys() print(our_iterable) #=> range(1,10). This is an object that implements our Iterable interface -i We can loop over it. +# We can loop over it. for i in our_iterable: print(i) # Prints one, two, three @@ -468,7 +470,10 @@ class Human(object): # A class attribute. It is shared by all instances of this class species = "H. sapiens" - # Basic initializer + # Basic initializer, this is called when this class is instantiated. + # Note that the double leading and trailing underscores denote objects + # or attributes that are used by python but that live in user-controlled + # namespaces. You should not invent such names on your own. def __init__(self, name): # Assign the argument to the instance's name attribute self.name = name @@ -554,9 +559,11 @@ def double_numbers(iterable): # double_numbers. # Note range is a generator too. Creating a list 1-900000000 would take lot of # time to be made -_range = range(1, 900000000) +# We use a trailing underscore in variable names when we want to use a name that +# would normally collide with a python keyword +range_ = range(1, 900000000) # will double all numbers until a result >=30 found -for i in double_numbers(_range): +for i in double_numbers(range_): print(i) if i >= 30: break @@ -569,10 +576,10 @@ for i in double_numbers(_range): from functools import wraps -def beg(_say): - @wraps(_say) +def beg(target_function): + @wraps(target_function) def wrapper(*args, **kwargs): - msg, say_please = _say(*args, **kwargs) + msg, say_please = target_function(*args, **kwargs) if say_please: return "{} {}".format(msg, "Please! I am poor :(") return msg diff --git a/zh-cn/julia-cn.html.markdown b/zh-cn/julia-cn.html.markdown new file mode 100644 index 00000000..7afc9043 --- /dev/null +++ b/zh-cn/julia-cn.html.markdown @@ -0,0 +1,729 @@ +--- +language: julia +filename: learn-julia-zh.jl +contributors: + - ["Jichao Ouyang", "http://oyanglul.us"] +translators: + - ["Jichao Ouyang", "http://oyanglul.us"] +lang: zh-cn +--- + +```ruby +# 单行注释只需要一个井号 +#= 多行注释 + 只需要以 '#=' 开始 '=#' 结束 + 还可以嵌套. +=# + +#################################################### +## 1. 原始类型与操作符 +#################################################### + +# Julia 中一切皆是表达式。 + +# 这是一些基本数字类型. +3 # => 3 (Int64) +3.2 # => 3.2 (Float64) +2 + 1im # => 2 + 1im (Complex{Int64}) +2//3 # => 2//3 (Rational{Int64}) + +# 支持所有的普通中缀操作符。 +1 + 1 # => 2 +8 - 1 # => 7 +10 * 2 # => 20 +35 / 5 # => 7.0 +5 / 2 # => 2.5 # 用 Int 除 Int 永远返回 Float +div(5, 2) # => 2 # 使用 div 截断小数点 +5 \ 35 # => 7.0 +2 ^ 2 # => 4 # 次方, 不是二进制 xor +12 % 10 # => 2 + +# 用括号提高优先级 +(1 + 3) * 2 # => 8 + +# 二进制操作符 +~2 # => -3 # 非 +3 & 5 # => 1 # 与 +2 | 4 # => 6 # 或 +2 $ 4 # => 6 # 异或 +2 >>> 1 # => 1 # 逻辑右移 +2 >> 1 # => 1 # 算术右移 +2 << 1 # => 4 # 逻辑/算术 右移 + +# 可以用函数 bits 查看二进制数。 +bits(12345) +# => "0000000000000000000000000000000000000000000000000011000000111001" +bits(12345.0) +# => "0100000011001000000111001000000000000000000000000000000000000000" + +# 布尔值是原始类型 +true +false + +# 布尔操作符 +!true # => false +!false # => true +1 == 1 # => true +2 == 1 # => false +1 != 1 # => false +2 != 1 # => true +1 < 10 # => true +1 > 10 # => false +2 <= 2 # => true +2 >= 2 # => true +# 比较可以串联 +1 < 2 < 3 # => true +2 < 3 < 2 # => false + +# 字符串可以由 " 创建 +"This is a string." + +# 字符字面量可用 ' 创建 +'a' + +# 可以像取数组取值一样用 index 取出对应字符 +"This is a string"[1] # => 'T' # Julia 的 index 从 1 开始 :( +# 但是对 UTF-8 无效, +# 因此建议使用遍历器 (map, for loops, 等). + +# $ 可用于字符插值: +"2 + 2 = $(2 + 2)" # => "2 + 2 = 4" +# 可以将任何 Julia 表达式放入括号。 + +# 另一种格式化字符串的方式是 printf 宏. +@printf "%d is less than %f" 4.5 5.3 # 5 is less than 5.300000 + +# 打印字符串很容易 +println("I'm Julia. Nice to meet you!") + +#################################################### +## 2. 变量与集合 +#################################################### + +# 给变量赋值就是声明变量 +some_var = 5 # => 5 +some_var # => 5 + +# 访问未声明变量会抛出异常 +try + some_other_var # => ERROR: some_other_var not defined +catch e + println(e) +end + +# 变量名需要以字母开头. +# 之后任何字母，数字，下划线，叹号都是合法的。 +SomeOtherVar123! = 6 # => 6 + +# 甚至可以用 unicode 字符 +☃ = 8 # => 8 +# 用数学符号非常方便 +2 * π # => 6.283185307179586 + +# 注意 Julia 的命名规约: +# +# * 变量名为小写，单词之间以下划线连接('\_')。 +# +# * 类型名以大写字母开头，单词以 CamelCase 方式连接。 +# +# * 函数与宏的名字小写，无下划线。 +# +# * 会改变输入的函数名末位为 !。 +# 这类函数有时被称为 mutating functions 或 in-place functions. + +# 数组存储一列值，index 从 1 开始。 +a = Int64[] # => 0-element Int64 Array + +# 一维数组可以以逗号分隔值的方式声明。 +b = [4, 5, 6] # => 包含 3 个 Int64 类型元素的数组: [4, 5, 6] +b[1] # => 4 +b[end] # => 6 + +# 二维数组以分号分隔维度。 +matrix = [1 2; 3 4] # => 2x2 Int64 数组: [1 2; 3 4] + +# 使用 push! 和 append! 往数组末尾添加元素 +push!(a,1) # => [1] +push!(a,2) # => [1,2] +push!(a,4) # => [1,2,4] +push!(a,3) # => [1,2,4,3] +append!(a,b) # => [1,2,4,3,4,5,6] + +# 用 pop 弹出末尾元素 +pop!(b) # => 6 and b is now [4,5] + +# 可以再放回去 +push!(b,6) # b 又变成了 [4,5,6]. + +a[1] # => 1 # 永远记住 Julia 的 index 从 1 开始! + +# 用 end 可以直接取到最后索引. 可用作任何索引表达式 +a[end] # => 6 + +# 还支持 shift 和 unshift +shift!(a) # => 返回 1，而 a 现在时 [2,4,3,4,5,6] +unshift!(a,7) # => [7,2,4,3,4,5,6] + +# 以叹号结尾的函数名表示它会改变参数的值 +arr = [5,4,6] # => 包含三个 Int64 元素的数组: [5,4,6] +sort(arr) # => [4,5,6]; arr 还是 [5,4,6] +sort!(arr) # => [4,5,6]; arr 现在是 [4,5,6] + +# 越界会抛出 BoundsError 异常 +try + a[0] # => ERROR: BoundsError() in getindex at array.jl:270 + a[end+1] # => ERROR: BoundsError() in getindex at array.jl:270 +catch e + println(e) +end + +# 错误会指出发生的行号，包括标准库 +# 如果你有 Julia 源代码，你可以找到这些地方 + +# 可以用 range 初始化数组 +a = [1:5] # => 5-element Int64 Array: [1,2,3,4,5] + +# 可以切割数组 +a[1:3] # => [1, 2, 3] +a[2:end] # => [2, 3, 4, 5] + +# 用 splice! 切割原数组 +arr = [3,4,5] +splice!(arr,2) # => 4 ; arr 变成了 [3,5] + +# 用 append! 连接数组 +b = [1,2,3] +append!(a,b) # a 变成了 [1, 2, 3, 4, 5, 1, 2, 3] + +# 检查元素是否在数组中 +in(1, a) # => true + +# 用 length 获得数组长度 +length(a) # => 8 + +# Tuples 是 immutable 的 +tup = (1, 2, 3) # => (1,2,3) # an (Int64,Int64,Int64) tuple. +tup[1] # => 1 +try: + tup[1] = 3 # => ERROR: no method setindex!((Int64,Int64,Int64),Int64,Int64) +catch e + println(e) +end + +# 大多数组的函数同样支持 tuples +length(tup) # => 3 +tup[1:2] # => (1,2) +in(2, tup) # => true + +# 可以将 tuples 元素分别赋给变量 +a, b, c = (1, 2, 3) # => (1,2,3) # a is now 1, b is now 2 and c is now 3 + +# 不用括号也可以 +d, e, f = 4, 5, 6 # => (4,5,6) + +# 单元素 tuple 不等于其元素值 +(1,) == 1 # => false +(1) == 1 # => true + +# 交换值 +e, d = d, e # => (5,4) # d is now 5 and e is now 4 + + +# 字典Dictionaries store mappings +empty_dict = Dict() # => Dict{Any,Any}() + +# 也可以用字面量创建字典 +filled_dict = ["one"=> 1, "two"=> 2, "three"=> 3] +# => Dict{ASCIIString,Int64} + +# 用 [] 获得键值 +filled_dict["one"] # => 1 + +# 获得所有键 +keys(filled_dict) +# => KeyIterator{Dict{ASCIIString,Int64}}(["three"=>3,"one"=>1,"two"=>2]) +# 注意，键的顺序不是插入时的顺序 + +# 获得所有值 +values(filled_dict) +# => ValueIterator{Dict{ASCIIString,Int64}}(["three"=>3,"one"=>1,"two"=>2]) +# 注意，值的顺序也一样 + +# 用 in 检查键值是否已存在，用 haskey 检查键是否存在 +in(("one", 1), filled_dict) # => true +in(("two", 3), filled_dict) # => false +haskey(filled_dict, "one") # => true +haskey(filled_dict, 1) # => false + +# 获取不存在的键的值会抛出异常 +try + filled_dict["four"] # => ERROR: key not found: four in getindex at dict.jl:489 +catch e + println(e) +end + +# 使用 get 可以提供默认值来避免异常 +# get(dictionary,key,default_value) +get(filled_dict,"one",4) # => 1 +get(filled_dict,"four",4) # => 4 + +# 用 Sets 表示无序不可重复的值的集合 +empty_set = Set() # => Set{Any}() +# 初始化一个 Set 并定义其值 +filled_set = Set(1,2,2,3,4) # => Set{Int64}(1,2,3,4) + +# 添加值 +push!(filled_set,5) # => Set{Int64}(5,4,2,3,1) + +# 检查是否存在某值 +in(2, filled_set) # => true +in(10, filled_set) # => false + +# 交集，并集，差集 +other_set = Set(3, 4, 5, 6) # => Set{Int64}(6,4,5,3) +intersect(filled_set, other_set) # => Set{Int64}(3,4,5) +union(filled_set, other_set) # => Set{Int64}(1,2,3,4,5,6) +setdiff(Set(1,2,3,4),Set(2,3,5)) # => Set{Int64}(1,4) + + +#################################################### +## 3. 控制流 +#################################################### + +# 声明一个变量 +some_var = 5 + +# 这是一个 if 语句，缩进不是必要的 +if some_var > 10 + println("some_var is totally bigger than 10.") +elseif some_var < 10 # elseif 是可选的. + println("some_var is smaller than 10.") +else # else 也是可选的. + println("some_var is indeed 10.") +end +# => prints "some var is smaller than 10" + + +# For 循环遍历 +# Iterable 类型包括 Range, Array, Set, Dict, 以及 String. +for animal=["dog", "cat", "mouse"] + println("$animal is a mammal") + # 可用 $ 将 variables 或 expression 转换为字符串into strings +end +# prints: +# dog is a mammal +# cat is a mammal +# mouse is a mammal + +# You can use 'in' instead of '='. +for animal in ["dog", "cat", "mouse"] + println("$animal is a mammal") +end +# prints: +# dog is a mammal +# cat is a mammal +# mouse is a mammal + +for a in ["dog"=>"mammal","cat"=>"mammal","mouse"=>"mammal"] + println("$(a[1]) is a $(a[2])") +end +# prints: +# dog is a mammal +# cat is a mammal +# mouse is a mammal + +for (k,v) in ["dog"=>"mammal","cat"=>"mammal","mouse"=>"mammal"] + println("$k is a $v") +end +# prints: +# dog is a mammal +# cat is a mammal +# mouse is a mammal + +# While 循环 +x = 0 +while x < 4 + println(x) + x += 1 # x = x + 1 +end +# prints: +# 0 +# 1 +# 2 +# 3 + +# 用 try/catch 处理异常 +try + error("help") +catch e + println("caught it $e") +end +# => caught it ErrorException("help") + + +#################################################### +## 4. 函数 +#################################################### + +# 用关键字 'function' 可创建一个新函数 +#function name(arglist) +# body... +#end +function add(x, y) + println("x is $x and y is $y") + + # 最后一行语句的值为返回 + x + y +end + +add(5, 6) # => 在 "x is 5 and y is 6" 后会打印 11 + +# 还可以定义接收可变长参数的函数 +function varargs(args...) + return args + # 关键字 return 可在函数内部任何地方返回 +end +# => varargs (generic function with 1 method) + +varargs(1,2,3) # => (1,2,3) + +# 省略号 ... 被称为 splat. +# 刚刚用在了函数定义中 +# 还可以用在函数的调用 +# Array 或者 Tuple 的内容会变成参数列表 +Set([1,2,3]) # => Set{Array{Int64,1}}([1,2,3]) # 获得一个 Array 的 Set +Set([1,2,3]...) # => Set{Int64}(1,2,3) # 相当于 Set(1,2,3) + +x = (1,2,3) # => (1,2,3) +Set(x) # => Set{(Int64,Int64,Int64)}((1,2,3)) # 一个 Tuple 的 Set +Set(x...) # => Set{Int64}(2,3,1) + + +# 可定义可选参数的函数 +function defaults(a,b,x=5,y=6) + return "$a $b and $x $y" +end + +defaults('h','g') # => "h g and 5 6" +defaults('h','g','j') # => "h g and j 6" +defaults('h','g','j','k') # => "h g and j k" +try + defaults('h') # => ERROR: no method defaults(Char,) + defaults() # => ERROR: no methods defaults() +catch e + println(e) +end + +# 还可以定义键值对的参数 +function keyword_args(;k1=4,name2="hello") # note the ; + return ["k1"=>k1,"name2"=>name2] +end + +keyword_args(name2="ness") # => ["name2"=>"ness","k1"=>4] +keyword_args(k1="mine") # => ["k1"=>"mine","name2"=>"hello"] +keyword_args() # => ["name2"=>"hello","k1"=>4] + +# 可以组合各种类型的参数在同一个函数的参数列表中 +function all_the_args(normal_arg, optional_positional_arg=2; keyword_arg="foo") + println("normal arg: $normal_arg") + println("optional arg: $optional_positional_arg") + println("keyword arg: $keyword_arg") +end + +all_the_args(1, 3, keyword_arg=4) +# prints: +# normal arg: 1 +# optional arg: 3 +# keyword arg: 4 + +# Julia 有一等函数 +function create_adder(x) + adder = function (y) + return x + y + end + return adder +end + +# 这是用 "stabby lambda syntax" 创建的匿名函数 +(x -> x > 2)(3) # => true + +# 这个函数和上面的 create_adder 一模一样 +function create_adder(x) + y -> x + y +end + +# 你也可以给内部函数起个名字 +function create_adder(x) + function adder(y) + x + y + end + adder +end + +add_10 = create_adder(10) +add_10(3) # => 13 + + +# 内置的高阶函数有 +map(add_10, [1,2,3]) # => [11, 12, 13] +filter(x -> x > 5, [3, 4, 5, 6, 7]) # => [6, 7] + +# 还可以使用 list comprehensions 替代 map +[add_10(i) for i=[1, 2, 3]] # => [11, 12, 13] +[add_10(i) for i in [1, 2, 3]] # => [11, 12, 13] + +#################################################### +## 5. 类型 +#################################################### + +# Julia 有类型系统 +# 所有的值都有类型；但变量本身没有类型 +# 你可以用 `typeof` 函数获得值的类型 +typeof(5) # => Int64 + +# 类型是一等值 +typeof(Int64) # => DataType +typeof(DataType) # => DataType +# DataType 是代表类型的类型，也代表他自己的类型 + +# 类型可用作文档化，优化，以及调度 +# 并不是静态检查类型 + +# 用户还可以自定义类型 +# 跟其他语言的 records 或 structs 一样 +# 用 `type` 关键字定义新的类型 + +# type Name +# field::OptionalType +# ... +# end +type Tiger + taillength::Float64 + coatcolor # 不附带类型标注的相当于 `::Any` +end + +# 构造函数参数是类型的属性 +tigger = Tiger(3.5,"orange") # => Tiger(3.5,"orange") + +# 用新类型作为构造函数还会创建一个类型 +sherekhan = typeof(tigger)(5.6,"fire") # => Tiger(5.6,"fire") + +# struct 类似的类型被称为具体类型 +# 他们可被实例化但不能有子类型 +# 另一种类型是抽象类型 + +# abstract Name +abstract Cat # just a name and point in the type hierarchy + +# 抽象类型不能被实例化，但是可以有子类型 +# 例如，Number 就是抽象类型 +subtypes(Number) # => 6-element Array{Any,1}: + # Complex{Float16} + # Complex{Float32} + # Complex{Float64} + # Complex{T<:Real} + # ImaginaryUnit + # Real +subtypes(Cat) # => 0-element Array{Any,1} + +# 所有的类型都有父类型; 可以用函数 `super` 得到父类型. +typeof(5) # => Int64 +super(Int64) # => Signed +super(Signed) # => Real +super(Real) # => Number +super(Number) # => Any +super(super(Signed)) # => Number +super(Any) # => Any +# 所有这些类型，除了 Int64, 都是抽象类型. + +# <: 是类型集成操作符 +type Lion <: Cat # Lion 是 Cat 的子类型 + mane_color + roar::String +end + +# 可以继续为你的类型定义构造函数 +# 只需要定义一个同名的函数 +# 并调用已有的构造函数设置一个固定参数 +Lion(roar::String) = Lion("green",roar) +# 这是一个外部构造函数，因为他再类型定义之外 + +type Panther <: Cat # Panther 也是 Cat 的子类型 + eye_color + Panther() = new("green") + # Panthers 只有这个构造函数，没有默认构造函数 +end +# 使用内置构造函数，如 Panther，可以让你控制 +# 如何构造类型的值 +# 应该尽可能使用外部构造函数而不是内部构造函数 + +#################################################### +## 6. 多分派 +#################################################### + +# 在Julia中, 所有的具名函数都是类属函数 +# 这意味着他们都是有很大小方法组成的 +# 每个 Lion 的构造函数都是类属函数 Lion 的方法 + +# 我们来看一个非构造函数的例子 + +# Lion, Panther, Tiger 的 meow 定义为 +function meow(animal::Lion) + animal.roar # 使用点符号访问属性 +end + +function meow(animal::Panther) + "grrr" +end + +function meow(animal::Tiger) + "rawwwr" +end + +# 试试 meow 函数 +meow(tigger) # => "rawwr" +meow(Lion("brown","ROAAR")) # => "ROAAR" +meow(Panther()) # => "grrr" + +# 再看看层次结构 +issubtype(Tiger,Cat) # => false +issubtype(Lion,Cat) # => true +issubtype(Panther,Cat) # => true + +# 定义一个接收 Cats 的函数 +function pet_cat(cat::Cat) + println("The cat says $(meow(cat))") +end + +pet_cat(Lion("42")) # => prints "The cat says 42" +try + pet_cat(tigger) # => ERROR: no method pet_cat(Tiger,) +catch e + println(e) +end + +# 在面向对象语言中，通常都是单分派 +# 这意味着分派方法是通过第一个参数的类型决定的 +# 在Julia中, 所有参数类型都会被考虑到 + +# 让我们定义有多个参数的函数，好看看区别 +function fight(t::Tiger,c::Cat) + println("The $(t.coatcolor) tiger wins!") +end +# => fight (generic function with 1 method) + +fight(tigger,Panther()) # => prints The orange tiger wins! +fight(tigger,Lion("ROAR")) # => prints The orange tiger wins! + +# 让我们修改一下传入具体为 Lion 类型时的行为 +fight(t::Tiger,l::Lion) = println("The $(l.mane_color)-maned lion wins!") +# => fight (generic function with 2 methods) + +fight(tigger,Panther()) # => prints The orange tiger wins! +fight(tigger,Lion("ROAR")) # => prints The green-maned lion wins! + +# 把 Tiger 去掉 +fight(l::Lion,c::Cat) = println("The victorious cat says $(meow(c))") +# => fight (generic function with 3 methods) + +fight(Lion("balooga!"),Panther()) # => prints The victorious cat says grrr +try + fight(Panther(),Lion("RAWR")) # => ERROR: no method fight(Panther,Lion) +catch +end + +# 在试试让 Cat 在前面 +fight(c::Cat,l::Lion) = println("The cat beats the Lion") +# => Warning: New definition +# fight(Cat,Lion) at none:1 +# is ambiguous with +# fight(Lion,Cat) at none:2. +# Make sure +# fight(Lion,Lion) +# is defined first. +#fight (generic function with 4 methods) + +# 警告说明了无法判断使用哪个 fight 方法 +fight(Lion("RAR"),Lion("brown","rarrr")) # => prints The victorious cat says rarrr +# 结果在老版本 Julia 中可能会不一样 + +fight(l::Lion,l2::Lion) = println("The lions come to a tie") +fight(Lion("RAR"),Lion("brown","rarrr")) # => prints The lions come to a tie + + +# Under the hood +# 你还可以看看 llvm 以及生成的汇编代码 + +square_area(l) = l * l # square_area (generic function with 1 method) + +square_area(5) #25 + +# 给 square_area 一个整形时发生什么 +code_native(square_area, (Int32,)) + # .section __TEXT,__text,regular,pure_instructions + # Filename: none + # Source line: 1 # Prologue + # push RBP + # mov RBP, RSP + # Source line: 1 + # movsxd RAX, EDI # Fetch l from memory? + # imul RAX, RAX # Square l and store the result in RAX + # pop RBP # Restore old base pointer + # ret # Result will still be in RAX + +code_native(square_area, (Float32,)) + # .section __TEXT,__text,regular,pure_instructions + # Filename: none + # Source line: 1 + # push RBP + # mov RBP, RSP + # Source line: 1 + # vmulss XMM0, XMM0, XMM0 # Scalar single precision multiply (AVX) + # pop RBP + # ret + +code_native(square_area, (Float64,)) + # .section __TEXT,__text,regular,pure_instructions + # Filename: none + # Source line: 1 + # push RBP + # mov RBP, RSP + # Source line: 1 + # vmulsd XMM0, XMM0, XMM0 # Scalar double precision multiply (AVX) + # pop RBP + # ret + # +# 注意 只要参数中又浮点类型，Julia 就使用浮点指令 +# 让我们计算一下圆的面积 +circle_area(r) = pi * r * r # circle_area (generic function with 1 method) +circle_area(5) # 78.53981633974483 + +code_native(circle_area, (Int32,)) + # .section __TEXT,__text,regular,pure_instructions + # Filename: none + # Source line: 1 + # push RBP + # mov RBP, RSP + # Source line: 1 + # vcvtsi2sd XMM0, XMM0, EDI # Load integer (r) from memory + # movabs RAX, 4593140240 # Load pi + # vmulsd XMM1, XMM0, QWORD PTR [RAX] # pi * r + # vmulsd XMM0, XMM0, XMM1 # (pi * r) * r + # pop RBP + # ret + # + +code_native(circle_area, (Float64,)) + # .section __TEXT,__text,regular,pure_instructions + # Filename: none + # Source line: 1 + # push RBP + # mov RBP, RSP + # movabs RAX, 4593140496 + # Source line: 1 + # vmulsd XMM1, XMM0, QWORD PTR [RAX] + # vmulsd XMM0, XMM1, XMM0 + # pop RBP + # ret + # +``` |