Possible to create class aliases dynamically?

Question

Got this class:

class Mass-lb is Mass {
    method new(Rat:D() $value = 1.0) {
        self.bless(
            :abbr('lb'),
            :base_value(453.59237),
            :$value,
        );
    }
}

I have created aliases like this:

class Mass-lbs is Mass-lb { }
class Mass-pound is Mass-lb { }
class Mass-pounds is Mass-lb { }
class Mass-pnds is Mass-lb { }

But I'd prefer to do something like this:

my @lb-syn = < lbs pounds pound pnds >;
for @lb-syn {
    EVAL 'class ::("Mass-$_") is Mass-lb {}';
}

This throws an error:

Name ::("Mass-$_") is not compile-time known, and can not serve as a package name

PHP has a built-in for creating aliases: https://www.php.net/manual/en/function.class-alias.php

I couldn't find anything similar for raku.

Answer 1

In RakuAST there's a class that you can call to create a new type. But that the RakuAST branch hasn't landed yet.

Until then, your approach using EVAL is valid, you just need to make it a bit simpler:

class Mass-lb { }
BEGIN "constant Mass-$_ = Mass-lb".EVAL
  for <lbs pounds pound pnds>;
my $mlb = Mass-lbs.new;

1. Make sure the aliases are created at BEGIN time.
2. No need to subclass, you can use a constant for aliasing.
3. Since constants are our by default, they're visible outside of the EVAL.