Provides a ?? !! equivalent that tests for definedness instread of trueness.
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lib/Operator change operators to multis Jul 4, 2016
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.travis.yml panda-- zef++ Jul 30, 2017
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Perl 6 provides control statements and operators to test for definedness instead of trueness, to provide ease of typing and a clear statement of intend from the programmer. Sadly there is currently no way to define your own ternary operators with Rakudo. However, we can emulate operators with 3 arguments with a chain of 2 infix operators, as long as we provide a type for the 2nd infix to handle dispatch properly.


use v6;
use Operator::defined-alternation;

my $falsish = 2 but False;
say $falsish ?// 'defined' !! 'undefined';
# OUTPUT: defined
# What is equivalent to:
say $falsish.defined ?? 'defined' !! 'undefined'; 
# OUTPUT: defined
# But opposed to:
say $falsish ?? 'true' !! 'false'; 
# OUTPUT: false 


(c) Wenzel P. P. Peppmeyer, Released under Artistic License 2.0.