CODEWITHSUNDEEP
perlsubroutineoptional-parametersfunction-signature
Evan Carroll
Evan Carroll

Reputation: 1

How do I declare an optional parameter in a signature?

Let's say I have 

use v5.026;
use feature 'signatures';

sub foo ($opt1, $opt2) {
  say $opt1 if $opt2;
}

main::foo(1,2);
main::foo(1);

Now I want to call foo with and without opt2:

foo(1);    # not currently accepted
foo(1,2);  # works fine

Upvotes: 3

Views: 546

Answers (2)

Grinnz
Grinnz

Reputation: 9231

You can also allow any number of optional parameters by ending the signature with an array, which will slurp any remaining arguments and also allows no values, like normal array assignment.

sub foo ($opt1, @opts) {

Upvotes: 3

Evan Carroll
Evan Carroll

Reputation: 1

Optional parameters with subroutine signatures require a defined default which is done with = default_value_expression. You can hard set this to undef:

sub foo ($opt1, $opt2 = undef) {
  say $opt1 if $opt2;
}

Upvotes: 6

Related Questions