From: GOTO Kentaro <gotoken@...>
Date: 2002-09-25T14:30:40+09:00
Subject: Re: are functions/methods "first class objects"?

At Wed, 25 Sep 2002 13:53:46 +0900,
Bulat Ziganshin wrote:
> sort_by "es", filenames  # sorts by extension then size
> sort_by "n", filenames   # sorts by filename w/o path and extension

Ruby 1.7 has Array#sort_by. The above are written as:

  filenames.sort_by{|i| File.extname(i), File.size(i)]}
  filenames.sort_by{|i| File.basename(i).sub(/\.[^.]+$/, "")}

> i want to create meta-function which returns function to sort (or just
> compare criterions) given ordering string:
> 
> sort_by "es"
> returns
> {|filename| [File.ext(filename), File.stat(filename).size] }
> 
> can you (and Ruby :) help me? -eval

How about:

  def criteria(switch)
    case switch
    when "es"
      Proc.new{|i| [File.extname(i), File.size(i)]}
    when "n"
      Proc.new{|i| File.basename(i).sub(/\.([^.]+)$/, "")}
    else
      Proc.new{|i| i}
    end
  end

  puts Dir["*"].sort_by(&criteria("es"))


-- Gotoken