Please Forward: Ruby Quiz Submission

ruby-talk
1

From: "Vasil Vangelovski" <vvangelovski@gmail.com>
Date: December 5, 2007 7:55:12 AM CST
To: submission@rubyquiz.com
Subject: Please Forward: Ruby Quiz Submission

#!/usr/bin/env ruby
#
# Created by Vasil Vangelovski on 2007-12-05.
# Copyright (c) 2007. All rights reserved.
#
# Solution for ruby quiz 148
# Thanx for posting something that can be solved on coffee-breaks

class String

#checks if the string is an operator
def op?
   return (self=='+')||(self=='-')||(self=='*')||(self=='/');
end

#returns true only for strings that represent integer or decimal numbers
def number?
   #there's a way to simplify this!!! (maybe later)
   int = false
   dec = false
   int = (/[0-9]+/.match(self)[0] == self) if !/[0-9]+/.match(self).nil?
   dec =(/[0-9]+[.]{0,1}[0-9]+/.match(self)[0] == self) if
!/[0-9]+[.]{0,1}[0-9]+/.match(self).nil?
   return int||dec
end

end

postfix_exp=ARGV[0]
tokens = postfix_exp.split(' ')

#the postfix->infix algo goes like this
stack =
tokens.each {|token|
if token.number?
   stack.push(token)
elsif token.op?
   string_top = stack.pop
   string_bottom = stack.pop
   #simple logic regarding operator precedence
   stack.push("(#{string_bottom}#{token}#{string_top})") if (token
=='+')||(token=='-')
   stack.push("#{string_bottom}#{token}#{string_top}") if (token
=='*')||(token=='/')
else
   #if it's not a number nor operator it's no valid
   puts "Invalid input!"
   exit(1)
end
}

infix = stack.to_s
#remove trailing and leading parenthesis if any
infix = infix[1..(infix.size-2)] if ((infix[0]==40)&&(infix[infix.size-1]==41))
puts infix

···

Begin forwarded message: