in reply to Re: Re: (Golf) Reversing RPN Notation
in thread (Golf) Reversing RPN Notation

With the hash that I gave, that solution is correct.

If the hash was, instead 

%o = ( '-' => 1,
       '+' => 2,
       '*' => 3,
       '/' => 3 );

[download]
then the code would produce the second, correct solution. In other words, the code's correct, the givens are just wrong :-)

Dr. Michael K. Neylon - mneylon-pm@masemware.com || "You've left the lens cap of your mind on again, Pinky" - The Brain

Replies are listed 'Best First'.
Re: Re: Re: Re: (Golf) Reversing RPN Notation
by MeowChow (Vicar) on May 21, 2001 at 22:27 UTC
    A few problems with this:
    • qw(2 3 4 * /) : you forgot to set '/' to 4
    • qw(2 3 4 - -) : this is the biggie 
       MeowChow                                   
               s aamecha.s a..a\u$&owag.print
[reply]
      Ok, it's probably going to depend on how you decide to pop off the stack. Given "N1 N2 o" in RPN where N1 and N2 are the numbers and o the operation, the LTR should be "N1 o N2".

      Yes, '/' would need to be 4. And yes, the second one poses the problem if there's no indication of order being important on an operation ("a op b" not being equal to "b op a"). Chipmunk's got part of the problem with associtivity in his 171 char solution, but I might need to restate the problem to handle this concept; at the time, I was only aiming for a general solution assuming that order didn't matter.

      Dr. Michael K. Neylon - mneylon-pm@masemware.com || "You've left the lens cap of your mind on again, Pinky" - The Brain
[reply]
        Almost. The rule that "a op b" != "b op a" is not the same rule as "a op (b op c)" != "(a op b) op c". The former is commutativity, while the latter is associativity. 
           MeowChow                                   
               s aamecha.s a..a\u$&owag.print
[reply]

In Section Meditations