Anonymous function: Difference between revisions

Revision as of 14:16, 18 February 2008

Revision as of 00:11, 20 February 2008

Line 229:

$foo = create_function("$x", "return $x*$x;");

echo $foo(10);

</source>

===Perl===

[[Perl]] supports anonymous functions, as follows:

<source lang="perl">

(sub { print "I got called\n" })->(); # 1. fully anonymous, called as created

my $squarer = sub { my $x = shift; $x * $x }; # 2. assigned to a variable

sub curry (&@) {

my ($sub, @args) = @_;

return sub { $sub->(@args, @_) }; # 3. as a return value of another function

}

# example of currying in Perl

sub sum { my $tot = 0; $tot += $_ for @_; $tot } # returns the sum of its arguments

my $curried = curry \&sum, 5, 7, 9;

print $curried->(1,2,3), "\n"; # prints 27 ( = 5 + 7 + 9 + 1 + 2 + 3 )

</source>

Other constructs take "bare blocks" as arguments, which serve a function similar to lambda functions of a single parameter, but don't have the same parameter-passing convention as functions -- @_ is not set.

<source lang="perl">

my @squares = map { $_ * $_ } 1..10; # map and grep don't use the 'sub' keyword

my @square2 = map $_ * $_, 1..10; # parentheses not required for a single expression

my @bad_example = map { print for @_ } 1..10; # values not passed like normal Perl function

</source>