From: Ross Bamford <rossrt@...>
Date: 2006-02-22T02:41:12+09:00
Subject: Re: Ruby Murray - Sub::Curry on Ruby Acid

On Wed, 2006-02-22 at 02:13 +0900, henon wrote:
> cool naming, nice functionality, easy using.
> AFAIK this is a instantiation of the Design Pattern called "Command" by
> the Gang of Four.
> i can not imagine a problem where i needed such flexible argument list.
> can anyone provide a motivation example in ruby?
> i'd suggest to add a small sample of usage to the docs.
> -- henon

Oh, I never said it was _useful_ :) 

Actually, I don't think there's anything in Ruby that can't be done
(better) some other way, but currying is one of those higher-order
things that every (decent) language should have ;).

Most of the examples I could contrive are in the docs - not sure if it's
linked prominently enough but did you see
http://rubymurray.rubyforge.org/files/doc/currybook_rdoc.html
?

James Edward Gray II also came up with a good example in the quiz
summary, based on his LazySpice spice (included in this release):

        # Lazy Evaluation meets Currying...
        class LazySpice < Curry::SpiceArg
          def initialize( &promise )
            super("LAZYSPICE")
            
            @promise = promise
          end
          
          def spice_arg( args )  # called to provide the missing argument
            [@promise.call]
          end
        end
        
        logger = lambda do |time, message|
          puts "[#{time.strftime('%I:%M:%S %p %m/%d/%y')}] #{message}"
        end
        
        log_now = logger.curry(LazySpice.new { Time.now })
        
        log_now["First Message."]   # => [12:47:53 PM 02/01/06] First Message.
        sleep 3
        log_now["Second Message."]  # => [12:47:56 PM 02/01/06] Second Message.

Again, not something that's difficult to do by other means (default
argument values for example) but, well, there you go.

-- 
Ross Bamford - rosco@roscopeco.REMOVE.co.uk