Re^2: how to avoid using index of array

I knew that it would be (and glad that it was) just a matter of time before you posted a Perl6 and zip operator solution.

I've been trying to figure out how to do that (before you made your post) using Perl 6 and the zip operator. Thanks for posting an example. For some reason I was expecting that the syntax should look more like this:

for( @male Z @female )->[$m,$f] {
    # ....
}
[download]

But apparently not. ;) Also, how would you push a stringified concatenation onto a new array? In Perl5 either of these would do WIM:

my @married;
foreach( 0 .. $#male ) {
    push @married, "$male[$_] $female[$_]";
}
# OR .....
my @married = map { "$male[$_] $female[$_]" } 0 .. $#male;

# OR with List::MoreUtils::pairwise
my @married = pairwise{ "$a $b" } @male, @female;
[download]

...or you could forgo interpolation and use the (.) dot operator.

I've been puzzling over a Perl6-ish, Zip-operator-ish way to do the same.

Dave

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Re^3: how to avoid using index of array by moritz (Cardinal) on Nov 13, 2011 at 08:27 UTC
For some reason I was expecting that the syntax should look more like this: `for( @male Z @female )->[$m,$f] { # .... }` [download] Close. Two things got into your way. The first is syntactic: you need a space between `for` and `(`. The reason is that (nearly) everything of the form `identifier(...)` is parsed as a subroutine call. That way keywords don't conflict with function names, making it more robust to introduce new syntax. The second one is a bit more interesting. In a signature, `[$m, $f]` stands for a single parameter, which is taken as a list, and unpacked into the two variables. But `@list1 Z @list2` returns a list of lists which flattens the sublists when you iterate over it. To stop that flattening, you can write `for (@male Z @female).tree ->[$m,$f] { # .... }` [download] which indeed works in current Rakudo. Also, how would you push a stringified concatenation onto a new array? Several ways: `my @array; for @male Z @female -> $m, $f { push @array, "$m $f; # or @array.push: "$m $f"; # or @array.push: $m ~ ' ' ~ $f } # or my @array = (@male Z @female).map("$^a $^b");` [download] Since Z can also be used as a meta operator, you can also get zip and concatenation in one go, using `Z~`: `my @array = @male Z~ @female; # without joining space` [download] To get the space between the two operands, you can use one of these tricks: `# with the list repetition operator: @array = @male Z~ ' ' xx @male Z~ @female; # with cross instead of zip: @array = @male X~ ' ' Z~ @female;` [download] All of these solutions work with current Rakudo. Perl 6 - second systems done right	[reply] [d/l] [select]

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Re^3: how to avoid using index of array
by moritz (Cardinal) on Nov 13, 2011 at 08:27 UTC

For some reason I was expecting that the syntax should look more like this:
for( @male Z @female )->[$m,$f] { # .... }
[download]

Close. Two things got into your way. The first is syntactic: you need a space between for and (. The reason is that (nearly) everything of the form identifier(...) is parsed as a subroutine call. That way keywords don't conflict with function names, making it more robust to introduce new syntax.

The second one is a bit more interesting. In a signature, [$m, $f] stands for a single parameter, which is taken as a list, and unpacked into the two variables. But @list1 Z @list2 returns a list of lists which flattens the sublists when you iterate over it. To stop that flattening, you can write

for (@male Z @female).tree ->[$m,$f] {
    # ....
}
[download]

which indeed works in current Rakudo.

Also, how would you push a stringified concatenation onto a new array?

Several ways:

my @array;
for @male Z @female -> $m, $f {
    push @array, "$m $f;
    # or
    @array.push: "$m $f";
    # or
    @array.push: $m ~ ' ' ~ $f
}

# or

my @array = (@male Z @female).map("$^a $^b");
[download]

Since Z can also be used as a meta operator, you can also get zip and concatenation in one go, using Z~:

my @array = @male Z~ @female; # without joining space
[download]

To get the space between the two operands, you can use one of these tricks:

# with the list repetition operator:
@array = @male Z~ ' ' xx @male Z~ @female;

# with cross instead of zip:
@array = @male X~ ' ' Z~ @female;
[download]

All of these solutions work with current Rakudo.

Perl 6 - second systems done right

[reply]
[d/l]
[select]