From: Gregory Marton <q8pb97u001@...>
Date: 2008-02-24T22:46:14+09:00
Subject: Re: passing method references in python & ruby

What bugs me about ruby is that I can't do this
def add_one(n)
  n + 1
end
[3,6,8].map(add_one)
 => [4,7,9]


I can't even do it more explicitly, because map won't take anything 
other than a block:

irb(main):001:0> class A; def A.addone(x); x + 1; end; end
=> nil
irb(main):002:0> A.method(:addone)
=> #<Method: A.addone>
irb(main):003:0> [3,6,8].map{|x| x + 1}
=> [4, 7, 9]
irb(main):004:0> [3,6,8].map(A.method(:addone))
ArgumentError: wrong number of arguments (1 for 0)
        from (irb):4:in `map'
        from (irb):4
irb(main):005:0> [3,6,8].map(Proc.new{|x| A.method(:addone).call(x)})
ArgumentError: wrong number of arguments (1 for 0)
        from (irb):5:in `map'
        from (irb):5
irb(main):006:0> [3,6,8].map Proc.new{|x| A.method(:addone).call(x)}
ArgumentError: wrong number of arguments (1 for 0)
        from (irb):6:in `map'
        from (irb):6


Any of these would be defeating the purpose of brevity anyway.  The best 
I can do is to make a block that calls the proc I want:

irb(main):007:0> [3,6,8].map{|x| A.method(:addone).call(x)}
=> [4, 7, 9]

or more simply:
irb(main):008:0> [3,6,8].map{|x| A.addone(x)}
=> [4, 7, 9]

this seems a waste of keystrokes, a cognitive indirection, and probably 
even a few processor cycles.  Is there a way?

Grem
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