Re^4: Idea: Moose Mutal Coercion

[educated_foo]

in reply to Re^3: Idea: Moose Mutal Coercion
in thread Idea: Moose Mutual Coercion

A less-distracting example might be a ball with mass, velocity, and momentum (calculate the third given two). I still think reaching for a lazy-building pile of Moose goop is wrong, since it's way easier to just have a cache:

sub momentum {
    my $self = shift;
    $self->{momentum} //= $self->{mass} * $self->{velocity};
}

but at least this may let people focus on the idea.

[BrowserUk]

You think that the OP is suggesting that Moose herders use his module so that they can type this:

package Equation_Problem; 
use Moose;
use MooseX::Invertible_Build;

has mass     => ( isa => Num);
has velocity => ( isa => Num);
has momentum => (
    isa => Num,
    invertible_build => {
        A => 'mass',
        B => 'velocity',
        via => 'A * B',
    },
);

To 'save' typing:

package Equation_Problem; 
use Moose;

has mass     => ( isa => Num);
has velocity => ( isa => Num);

sub momentum {
    my $self = shift;
    $self->mass * $self->velocity;
}

Hm. It can't be that in(s)ane.

[choroba]

No. I guess the OP wants a class which you can initialize with any two attributes, but you can then ask for all three.

[BrowserUk]

Ah! The hackers are gonna love this:

package Hash::PassPhrase; 
 use Moose;
 use MooseX::Invertible_Build;

 has passPhrase    => ( isa => Str );
 has salt          => ( isa => Str );
 has hash => (
     isa => Str,
     invertible_build => {
         A => 'salt',
         B => 'passPhrase',
         via => 'crypt( A, B )',
     },
 );