Today I was reading S06 from http://dev.perl.org/perl6/doc/design/syn/S06.html, and I have some perplexities on what's written there.
1) it's written:
$pair = :when<now>;
doit $pair,1,2,3; # always a positional arg
doit *$pair,1,2,3; # always a named arg
but also:
To pass pairs out of hash without their being interpreted as named
parameters, use
doit %hash<a>:p,1,2,3;
doit %hash{'b'}:p,1,2,3;
instead.
I interpret the last sentence as meaning that:
$hash<a>=:a<2>; doit %hash<a>;
would be equivalent to:
doit :a<2>
which contradicts what is written earlier... I'd assume I'd have to
write:
doit *(%hash<a>);
for the pair to be used as a named argument. What am I missing?
2) Consider:
doit %*hash; # 1 arg, the global hash
doit *%hash; # n args, the key-value pairs in the hash
I think I'll use a lot of C-t while writing Perl6 code...
3) What does the second line in:
push @array, :a<1>;
say *pop(@array);
mean? I'd parse it as 'say (*pop)(@array)', that is, call the global
'pop' subroutine. But the text around this example seems to imply that
it is to be parsed as 'say *(pop(@array))', i.e. execute 'pop' and splat
the result. What gives?
4) It's written:
(Conjectural: Within the body you may also use exists on the
parameter name to determine whether it was passed. Maybe this will have
to be restricted to the ? form, unless we're willing to admit that a
parameter could be simultaneously defined and non-existant.)
Ok, this is 'conjectural', but... if i don't pass a parameter in an
invocation, and that parameter had a defined default, that it would be
both defined and non-passed... here I'm sure I'm missing something
5) while talking about pipes, it says that
(0..2; 'a'..'c') ==> my @;tmp;
for @;tmp.zip { say }
produces
[0,'a']
[1,'b']
etc. Right. But then it says:
for @;tmp.each -> $i, $a { say "$i: $a" }
as far as I understand, this should say
0: undef
'a': undef
etc., since 'each' is visiting the multidimensional array 'by rows',
and producing 1 value at a time, which when bound to the 2-ary signature
would leave the $a parameter without a value, and so undef (I'm assuming
that pointy sub positional parameters are implicitly optional, otherwise
that statement would be a run-time error). I'm pretty sure I don't know
what 'each' does...
6) It's written:
Every lexical scope gets its own implicitly declared @; variable,
which is the default receiver.
To me, that is a variable with a null name ('@;' being a twigil).
Should it not be @;_ ?
I'll continue reading...
--
Dakkar - <Mobilis in mobile>
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