Hi,
Rob Kinyon wrote:
> What about the function compose() that would live in the module
> "keyword", imported by the incantation "use keyword qw( compose );"?
FWIW, I like "o" better -- function composing is very often used in FP,
and should therefore have a short name.
Luckily, it's very easy to define that:
sub *infix:<o>(Code $a, Code $b) {...}
> multimethod compose (@*List) {
> return {
> $_() for @List;
> };
> }
I don't that will work for functions that take arguments.
My take at it:
sub compose (Code [EMAIL PROTECTED]) {
# Note: We're losing compile-time type checking here.
return -> [EMAIL PROTECTED] is copy {
@args = $_([EMAIL PROTECTED]) for reverse @fs;
return @args;
};
}
sub f(Int $x) { 100 + $x }
sub g(Int $x) { 2 * $x }
my $f_o_g = compose &f, &g;
say $f_o_g(42); # 184
Is there a way to not lose compile-time type checking, so that the
following will barf at compile time?
sub f(Int $x) returns Int { 100 + $x }
sub g(Int $a, Int $b) returns Int {...}
my $f_o_g = compose &f, &g; # should die
--Ingo
--
Linux, the choice of a GNU | Life would be so much easier if we could
generation on a dual AMD | just look at the source code.
Athlon! | -- Dave Olson
