From: Ken Bloom <kbloom@...>
Date: 2007-12-03T03:40:01+09:00
Subject: Re: [QUIZ] Postfix to Infix (#148)

On Sun, 02 Dec 2007 12:14:10 -0500, Pawel Radecki wrote:

> Hello everybody,
> 
> Here's my solution. I know it's pretty long but I'm still learning...
> BIG thanks for the quiz!
> 
> 
> 
> #!/usr/bin/env ruby
> 
> # Solution to Ruby Quiz #148 (see http://www.rubyquiz.com/quiz148.html)
> # by Pawel Radecki (pawel.j.radecki@gmail.com).
> 
> # Note1: There may be couple of different and correct postfix to infix #
> transformations but this program only gives one and ignores others. #
> # Example:
> # postfix: 1 2 + 4 * 5 + 3 -
> # infix: (1 + 2) * 4 + 5 - 3
> # infix: (1+2)*4+5-3
> # infix: 5 + (1 + 2) * 4 - 3
> # infix: 5 + 4 * (1 + 2) - 3
> # ... (there are more)
> 
> # Note2: Unary operators not supported!
> 
> # Note3: I don't know why ^ in input argument doesn't work, anybody
> knows...?

It appears to be this regex over here. You need to escape the ^ if you 
want to use it in a regex, because ^ signals the beginning of a line in a 
regex.

>             @string =~
> /([0-9\.]+|[a-z]+)\s([0-9\.]+|[a-z]+)\s((\*\*)|(V)|\+|\*|\/|-)/

--Ken

-- 
Ken (Chanoch) Bloom. PhD candidate. Linguistic Cognition Laboratory.
Department of Computer Science. Illinois Institute of Technology.
http://www.iit.edu/~kbloom1/