From: GFunk913@...
Date: 2006-01-07T14:38:01+09:00
Subject: Re: Iterator Fu Failing Me

Are "Write a new Enumerable method that mimics find but returns the
block result instead" or "do a less elegant solution involving
assignment" not acceptable solutions?

James Edward Gray II wrote:
> I have a group of classes, all implementing a parse?() class method.
> Calling parse?(token) will return the constructed object, if it can
> be parsed by this class, or false otherwise.
>
> I want to run a bunch of tokens through these classes, grabbing the
> first fit.  For example:
>
>    elements = tokens.map do |token|
>      ClassA.parse?(token) or
>      ClassB.parse?(token) or
>      ClassC.parse?(token)
>    end
>
> That works.  Now can anyone give me a version of the middle section
> that doesn't require I call parse?() 50 times?  I want something
> close to:
>
>    elements = tokens.map do |token|
>      [ClassA, ClassB, ClassC].find { |kind| kind.parse?(token) }
>    end
>
> Except that I want the return result of parse?(), instead of the
> class that took it.
> 
> Thanks for any tips you can offer.
> 
> James Edward Gray II