Monad-Result
An implementation of the result monad from OCaml. This allows the developer to completely avoid exceptions.
How to use
use Monad::Result;
sub my-error-causing-function($value --> Result) {
return Monad::Result::error('Bad value!') if $value eq 'bad'
Monad::Result::ok('Value was good!');
}
# Bind operator: >>=:
my-error-causing-function('bad') >>=: -> $value {
say $value; # Is not called because this is not bindable (it is an error!)
return Monad::Result::ok($value);
};
my-error-causing-function('abc') >>=: -> $value {
say $value; # Is said because this is bindable, it is OK!
return Monad::Result::ok($value);
};
# Map operator: >>=?
# Since this call results in OK, we can map it!
my $result = (my-error-causing-function('abc') >>=? -> $value {
$value ~ ' HELLO WORLD';
}); # Results in: Monad::Result::ok('abc HELLO WORLD');
say $result.is-ok; # True
# NOTE UNWRAP IS DANGEROUS!
say $result.unwrap; # 'abc HELLO WORLD';
How to install
zef install Monad::Result