From: Gavin Sinclair <gsinclair@...>
Date: 2003-01-22T11:25:44+09:00
Subject: Re: Ruby idiom (0...(expr)).map

On Wednesday, January 22, 2003, 4:17:08 AM, Martin wrote:

> More usefully, Range#map is a shortcut for Range.to_a.map, but since I
> most commonly want to start from 0, I thought a further shortcut for
> (0...n).map would make my code prettier.

> Frinstance, here's a snippet from some code I'm currently writing to
> format text into columns:

>   npages.times {|i| ranges.push((pagebreak * i)..(pagebreak*i+psize-1))}
>   ranges.each {|r|
>     page << r.map {|line| 
>       (0...ncols).map {|col| text[line + col*psize]}.join(col_sep)
>     }
>   }

> where I want an array each element of which is a function of the current
> index. Here it's not so bad, since I've already had occasion to define
> ncols, but if it were an inline expression, the code would start looking
> really messy.

Well, you always have "occasion" to define the "expr" in (0...expr).
If it's inline and messy, you create an expression variable.

I can't see that particular idiom disappearing in a hurry.  Have you
tried the shortcut yourself, with pleasant results?

  class Fixnum
    def map(&block)
      (0...self).map &block
    end
  end

Gavin