diff options
| -rw-r--r-- | perl6.html.markdown | 86 |
1 files changed, 84 insertions, 2 deletions
diff --git a/perl6.html.markdown b/perl6.html.markdown index 4ba76d6c..7a8c7525 100644 --- a/perl6.html.markdown +++ b/perl6.html.markdown @@ -78,11 +78,12 @@ unless False { say "It's not false !"; } + # if (true) say; # Won't work # `given`-`when` looks like other languages `switch`, but it's much more powerful thanks to smart matching : -given "foo bar" { # given just puts its argument into `$_`, and `when` uses it. - when /foo/ { # smart matching a string with a regex returns true if it matches +given "foo bar" { # given just puts its argument into `$_`, and `when` uses it using the "smart matching" operator. + when /foo/ { # you'll read about the smart-matching operator below say "Yay !"; } when $_.chars > 50 { # smart matching anything with True gives True, so you can also put "normal" conditionals @@ -118,4 +119,85 @@ for array { 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 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 + +## 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 +(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" + +### - `===` 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; + +## * 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 $obj2; # sort comparison using eqv semantics + +## * Generic ordering +3 before 4; # True +'b' after 'a'; # True + +## * Range constructors +3 .. 7; # 3 to 7, both included +### `^` on either side them exclusive on that side : +3 ^..^ 7; # 3 to 7, not included (basically `4 .. 6`) + +# * And, Or + +## Short-circuit (and tight) +$a && $b && $c; # returns the first argument that evaluates to False, or the last argument +$a || $b; ``` |