string_to_proc.rb

# The MIT License
# 
# Copyright (c) 2004-2008 Reginald Braithwaite
# Portions Copyright (c) 2006 Oliver Steele
# <http://reginald.braythwayt.com>  except as otherwise noted.
#
# See http://weblog.raganwald.com/2007/10/stringtoproc.html
#
# Ported from the String Lambdas in Oliver Steele's Functional Javascript
# http://osteele.com/sources/javascript/functional/
# 
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
# 
# The above Copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
# 
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
# THE SOFTWARE.
# 
# http://www.opensource.org/licenses/mit-license.php

class String
  unless ''.respond_to?(:to_proc)
    def to_proc &block
      params = []
      expr = self
      sections = expr.split(/\s*->\s*/m)
      if sections.length > 1 then
          eval sections.reverse!.inject { |e, p| "(Proc.new { |#{p.split(/\s/).join(', ')}| #{e} })" }, block && block.binding
      elsif expr.match(/\b_\b/)
          eval "Proc.new { |_| #{expr} }", block && block.binding
      else
          leftSection = expr.match(/^\s*(?:[+*\/%&|\^\.=<>\[]|!=)/m)
          rightSection = expr.match(/[+\-*\/%&|\^\.=<>!]\s*$/m)
          if leftSection || rightSection then
              if (leftSection) then
                  params.push('$left')
                  expr = '$left' + expr
              end
              if (rightSection) then
                  params.push('$right')
                  expr = expr + '$right'
              end
          else
              self.gsub(
                  /(?:\b[A-Z]|\.[a-zA-Z_$])[a-zA-Z_$\d]*|[a-zA-Z_$][a-zA-Z_$\d]*:|self|arguments|'(?:[^'\\]|\\.)*'|"(?:[^"\\]|\\.)*"/, ''
              ).scan(
                /([a-z_$][a-z_$\d]*)/i
              ) do |v|  
                params.push(v) unless params.include?(v)
              end
          end
          eval "Proc.new { |#{params.join(', ')}| #{expr} }", block && block.binding
      end
    end
  end
end