diff options
| -rw-r--r-- | perl6.html.markdown | 24 |
1 files changed, 16 insertions, 8 deletions
diff --git a/perl6.html.markdown b/perl6.html.markdown index f804ef86..6c13b793 100644 --- a/perl6.html.markdown +++ b/perl6.html.markdown @@ -197,6 +197,10 @@ say $x; #=> 52 ## Conditionals # - `if` +# Before talking about `if`, we need to know which values are "Truthy" (represent True), +# and which are "Falsey" (or "Falsy") -- meaning they represent False. +# Only these values are Falsey: (), 0, "0", Nil, A type, and of course False itself. +# Every other value is Truthy. if True { say "It's true !"; } @@ -341,7 +345,7 @@ say @array[^10]; # you can pass arrays as subscripts and it'll return an array o # so you'll end with an infinite loop. ## * And, Or -3 && 4; # True. Calls `.Bool` on `3` +3 && 4; # 4, which is Truthy. Calls `.Bool` on `4` and gets `True`. 0 || False; # False. Calls `.Bool` on `0` ## Short-circuit (and tight) versions of the above @@ -448,7 +452,7 @@ say ((*+3)/5)(5); #=> 1.6 # you can also use the implicit argument syntax, `$^` : map({ $^a + $^b + 3 }, @array); # same as the above -# Note : those are sorted lexicographically. `{ $^b / $^a }` is like `-> $a, b { $b / $a }` +# 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, @@ -813,24 +817,28 @@ sub postfix:<!>(Int $n) { [*] 2..$n; # using the reduce meta-operator ... See below ;-) ! } say 5!; #=> 120 - # (postfix is after) + # 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(); # needs the parentheses because it's a scalar + $r(); # You need the explicit parentheses to call the function in `$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 + # circumfix is around. Again, not whitespace. sub postcircumfix:<{ }>(Str $s, Int $idx) { # post-circumfix is "after a term, around something" $s.substr($idx, 1); @@ -915,7 +923,7 @@ for <well met young hero we shall meet later> { # (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` (flip-flop) and `fff` (flip-flop) is that +# 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: @@ -935,8 +943,8 @@ for <test start print this stop you stopped printing start printing again stop n # 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) { - .say if $_ > 50 ff *; # Once the flip-flop reached a number greater than 50, it'll never go back to `False` +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 } |