From: Brian Candler <B.Candler@...>
Date: 2003-07-22T01:57:40+09:00
Subject: Re: Proposal: Array#to_h, to simplify hash generation

On Tue, Jul 22, 2003 at 01:43:46AM +0900, Brian Candler wrote:
> The bit I don't like is Hash#<< taking an array of two elements, rather than
> having two arguments

I forgot about using Method#arity. New version attached... Brian.

class Array    # ditto for Enumerable
  def collect(dest=Array,*args)
    res = dest.new(*args)
    if res.method(:<<).arity == 1
      each do |item|
        res << yield(item)
      end
    else
      each do |item|
        res.send(:<<, *yield(item))
      end
    end
    res
  end
end

class Hash
  def <<(key,val)
    self[key] = val
  end
end

a = [["one","two"],["three","four"],["five","six"]]

p a.collect {|e| e[0]}
p a.collect(String,"") {|e| e[1]}
p a.collect(Hash) {|e| e}
p a.collect(Hash) {|k,v| [v,k]}   # like Hash#invert

def f(i) i*i; end

p [1, 2, 3].collect(Hash) { |i| [i, f(i)] }
p [1, 2, 3].collect(String,"") { |i| i.class.to_s }
p [1, 2, 3].collect(Array) { |i| Regexp.new(i.to_s) }