From: Mike Gold <mike.gold.4433@...>
Date: 2009-01-12T07:48:52+09:00
Subject: Re: functional programming

Brian Candler wrote:
> (2) to understand Mike's assertion 
> that Ruby lambdas are not first-class functions (i.e. "The difference 
> between lambda { } and a real first-class function is quite profound").

Ruby:

  mean = lambda { |*args|
    (args.inject(0) { |acc, x| acc + x })/args.size.to_f
  }
  data = [[1,2,3], [4,5,6,7]]

  data.map(&mean) # fail
  data.map(&:mean) # fail
  data.map { |*numbers| mean.call(*numbers) } # fail
  data.map { |numbers| mean.call(*numbers) } # phew, found it

Haskell:

  map mean data

On this example alone, I think my characterization of "quite profound" 
is justified.
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