Raku Land

eigenstates

cpan:ELIZABETH

Actions Status

NAME

eigenstates - expose the eigenstates of an object

SYNOPSIS

  use eigenstates;

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

  say eigenstates(42);     # 42

DESCRIPTION

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.

TECHNICAL BACKGROUND

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␤

with:

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

AUTHOR

Elizabeth Mattijsen liz@wenzperl.nl

Source can be located at: https://github.com/lizmat/eigenstates . Comments and Pull Requests are welcome.

COPYRIGHT AND LICENSE

Copyright 2020 Elizabeth Mattijsen

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