On Mon, Mar 09, 2009 at 11:38:29AM -0500, Patrick R. Michaud wrote:
: On Sun, Mar 08, 2009 at 09:31:19PM -0700, Larry Wall wrote:
: > On Sun, Mar 08, 2009 at 09:36:17PM +0100, Moritz Lenz wrote:
: > : But both pugs and rakudo respect the arity of the code ref passed to it,
: > : so that (1..6).map({$^a + $^b + $^c}) returns the list (6, 15), which is
: > : very nice and very DWIM'my.
: > :
: > : But it opens the question what should happen if there is a number of
: > : items in the list that's not easily divisible by the arity - should the
: > : rest just be padded with undef's? or just ignored? Or fail() with a
: > : friendly error message?
: >
: > I think the basic rule has to be simply can the signature bind to
: > the remaining arguments. If not, we get a warning on unused arguments.
: > We can mark arguments as optional if that's what we mean.
: > [...]
: > My gut feeling is that
: > placeholder variables probably should not be considered optional; in
: > most cases a non-divisible number of arguments indicates a logic error
: > in the program, and an earlier message is better, even at the expense
: > of thowing away some (possibly valid) partial data. Especially since
: > we do have a way to indicate that partial data is acceptable:
: >
: > -> $a, $b?, $c? { $a + ($b//0) + ($c//0) }
:
: Presumably whatever we decide for C<map()> also applies to C<for>, yes?
:
: for 1..4 -> $a, $b, $c { ... } # error
: for 1..4 -> $a, $b, $c? { ... } # error
: for 1..4 -> $a, $b?, $c? { ... } # ok
Yes, the only difference between C<for> and C<map> is that you can
only use C<for> at the start of a statement. But we're more liberal
about where statements are expected in Perl 6, so you can say things
like:
my @results = do for @list -> $x {...};
my @results = (for @list -> $x {...});
and either of those is equivalent to:
my @results = map -> $x {...}, @list;
I also Officially Don't Care if you use map in a void context. :)
Larry
