Note: I'm actually not talking about hyperoperators below, or
map/grep/sort. Just 'for'.
On Sat, 26 Jan 2002 12:32:06 -0600, Jonathan Scott Duff wrote:
> @result = for @a; @b -> $a; $b { $a op $b }
I'd like to chime in withthe people who have already said that the
semicolons are a bit confusing.
I'd like to propose a slightly different syntax. Is this maybe valid, or
have I missed a gaping problem?
# Simplest case: one data source, pulling elements one at a time,
# operating against a constant
@result = for @a -> ($a) { $a + 2 }
More formally, this would be:
for LIST -> LIST [[, LIST -> LIST]...] CLOSURE (returns: LIST)
So, you could write things like so:
# pull elements off two-by-two
for @a -> $x, $y { ... }
# flatten @a, @b together, pull elements off two-by-two
for @a, @b -> $x, $y { ... }
# pull one off @a, one off @b
for @a -> $x,
@b -> $y
{ ... }
# pull one off @a, two off @b
for @a -> $x,
@b -> $y, $z
{ ... }
Of course, all of these only DWIM if -> knows that it takes exactly one
item on the left, and a list on the right.
As an extra bit of magic, perhaps, when the only thing to the left of ->
is a scalar, it could reduce to this (in Perl5 terms):
# This Perl6:
for $_ -> $x { ... }
# is the same as this Perl5:
{
my $x = $_;
local ($_);
{ ... }
}
Dave Storrs
