gistfile1.txt

use v6;
unit module Units;

class Unit {
    has Rat $.magnitude;
    has %.units;
    multi method mergeUnits(Unit $u) {
        my %unitm = $u.units;
        my $op = &[+];
        for keys %!units -> $unit {
            if (%!units{$unit}:exists) { %!units{$unit} = $op(%!units{$unit}, %unitm{$unit}); }
            else {%!units{$unit} = %unitm{$unit};}
        }
        return self.cleanUnits();
    }

    method cleanUnits() {
        for keys %!units -> $unit {
            if (%!units{$unit} == 0) {%!units{$unit}:delete;}
        }
    }

    method isSameUnit(Unit $comp) {
        my %u = $comp.units;
        if (not %!units == %u) {
            return False;
        }
        for keys %!units -> $u {
            if (%!units{$u} != %u{$u}) {return False;}
        }
        return True;
    }

    method gist {
        my $unitString = "";
        my $negUnitString = "";
        for kv %!units -> $unit, $exp {
            if ($exp > 0) {$unitString = $unitString ~ $unit ~ "^" ~  $exp ~ "*";}
            else {$negUnitString = $unitString ~ $unit ~ "^" ~ (abs $exp) ~ "*";}
        }
        $unitString = ($!magnitude.gist) ~ " " ~ $unitString.chop;
        if ($negUnitString === "") {return $unitString;}
        return $unitString ~ "/" ~ $negUnitString.chop;
    }
}

multi sub infix:<==> (Units::Unit $x, Units::Unit $y) is export { 
    if (not $x.isSameUnit($y)) {die "Units do not match.";}
    return $x.magnitude == $y.magnitude;
}

multi sub infix:<===> (Units::Unit $x, Units::Unit $y) is export { 
    return $x.isSameUnit($y) && ($x.magnitude == $y.magnitude);
}
multi sub infix:<+>(Units::Unit $x, Units::Unit $y) is export {
    if (not $x.isSameUnit($y)) {die "Units do not match.";}
    return Unit.new(magnitude => $x.magnitude + $y.magnitude, units => $x.units);
}

multi sub infix:<->(Units::Unit $x, Units::Unit $y) is export {
    if (not $x.isSameUnit($y)) {die "Units do not match.";}
    return Unit.new(magnitude => $x.magnitude - $y.magnitude, units => $x.units);
}

multi sub infix:<*>(Units::Unit $x, Units::Unit $y) is export {
    return Unit.new(magnitude => $x.magnitude * $y.magnitude, units => $x.mergeUnits($y.units));
}

multi sub infix:</>(Units::Unit $x, Units::Unit $y) is export {
    return Unit.new(magnitude => $x.magnitude / $y.magnitude, units => $x.mergeUnits(&[-], $y));
}


my $a = Units::Unit.new(magnitude => 1.2, units => ("m" => 1));
my $b = Units::Unit.new(magnitude => 5.0, units => ("m" => 1));
my $c = Units::Unit.new(magnitude => 5.0, units => ("m" => 1, "s" => -1));

say $a * $b;


# ERROR: 
# Cannot call AUTOGEN(Units::Unit: Hash); none of these signatures match:
#    (Units::Unit $: Units::Unit $u, *%_)
# Cannot call mergeUnits(Units::Unit: Hash); none of these signatures match:
#    (Units::Unit $: Units::Unit $u, *%_)
#  in sub infix:<*> at lib/math/units.pm6 line 65
#  in block <unit> at lib/math/units.pm6 line 78