From: ahoward <ahoward@...>
Date: 2003-01-25T02:49:14+09:00
Subject: Re: Ruby idiom (0...(expr)).map

On Fri, 24 Jan 2003, Bulat Ziganshin wrote:

> Hello ahoward,
>
> Tuesday, January 21, 2003, 8:57:22 PM, you wrote:
>
> >> > I've found myself writing (0...(expr)).map (as an alternative to
> >> > a = []; expr.times {|i| a << ..}) often enough that I was wondering
> >> > whether to define it as a method of fixnum. Fixnum#map doesn't seem
> >> > quite right, though - any name suggestions?
>
> may be
>
> Array.new(expr) {|i| i}

i didn't actually write that post, but i've been thinking of simply having
new/initialize take a block... something like this :

class Array
  def self.init n = 0, o = nil, &b
    if b
      a = new n
      n.times {|i| a[i] = o ? b.call(o) : b.call(i)}
      a
    else
      self.new n, o
    end
  end
end


if $0 == __FILE__
  ary = [0,1,2]

  p Array.init 1, 42	                     # >> [42]
  p Array.init (3, []) {|a| a.clone}         # >> [[], [], []]
  p Array.init (3, ary) {|a| a.pop}          # >> [2, 1, 0]
  p Array.init (4) {|i| i}		     # >> [0, 1, 2, 3]
  p Array.init (2) {[rand]}		     # >> [[0.3466412831], [0.7881289076]]
end

if a default object is given, the block is called with that object, otherwise
the block is called with the index being initialized

<above using inject>
.... someone will fill this in ;-) ...
</above using inject>

-a

-- 

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 | Ara Howard
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