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eigenstates cpan:ELIZABETH last updated on 2020-11-29


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eigenstates - expose the eigenstates of an object


use eigenstates;

say eigenstates(1|2|3);  # 1 2 3

say eigenstates(42);     # 42


The eigenstates distribution exports a single subroutine called eigenstates that returns a list of the eigenstates of an object. For all objects except Junctions, that's a list with the given object. For a Junction, it returns the internal values (aka "eigenstates") as a List.


Developers starting to use Raku often wonder why there is Mu class that is the parent of the Any class, with the Any class being the default class. The reason for this is the existence of Junctions. If you look at the parent classes of e.g. Int:

say Int.^mro;       # ((Int) (Cool) (Any) (Mu))

However, if you look at the parent classes of Junction:

say Junction.^mro;  # ((Junction) (Mu))

you will notice that Junction is NOT a subclass of Any. It is that fact that makes autothreading of values inheriting from Any work.

As a consequence, if you want to create a subroutine / method with a signature that will take a Junction "as is", you will need to give it a Mu constraint. Compare the behaviour of:

sub auto-threading($value) {   # implicit Any
    say $value;
auto-threading( 42 | 666 );   # 42␤666␤


sub non-threading(Mu $value) {
    say $value;
non-threading( 42 | 666 );   # any(42, 666)


Elizabeth Mattijsen [email protected]

Source can be located at: . Comments and Pull Requests are welcome.


Copyright 2020 Elizabeth Mattijsen

This library is free software; you can redistribute it and/or modify it under the Artistic License 2.0.