From: Markus <markus@...>
Date: 2006-03-19T14:20:28+09:00
Subject: Re: can you enable coercion between types?

On Sat, 2006-03-18 at 17:11, ara.t.howard@noaa.gov wrote:

> try this:
> 
>      harp:~ > cat a.rb
>      class Duration
>        def initialize seconds
>          @seconds = seconds
>        end
>        def coerce other
>          if other.class == @seconds.class
>            [@seconds, other]
>          else
>            [Float(@seconds), Float(other)]
>          end
>        end

There's a gottcha here.  Coerce is used to implement double dispatch and
so needs to return the coerced values in the opposite order (see Pick
Axe)--(other,self), not (self,other).

The way you wrote it works fine for addition & multiplication, but
you'll pull your hair out the first time you try to subtract or divide.

--MarkusQ

P.S. And I think (as Tom noted) that "to_f" was the answer to the
original question.