From: Donald Patch <spamwhacker+rubyforum@...>
Date: 2007-08-26T05:25:10+09:00
Subject: Re: Combinations of numbers/operators?

Dan Zwell wrote:
> Do you know you are only dealing with four numbers? It makes quite a
> difference. A general algorithm to parenthesize all possible
> combinations isn't that hard in principle (recursively split an array of
> numbers, adding an operator and parentheses at each stage), but it's
> awkward to code, aspecially while maintaining the "all permutations of
> operations" that you originally asked about.

Yeah, I know; this goes much farther than the original question. It 
occurred to me after looking at the output that I hadn't considered 
stuff like making the first integer a negative number or the impact of 
grouping/parentheses. Duh.

Here's a related question: is there a math library in Ruby that would 
allow me to "solve for" a given number given several inputs? For 
example, I have the number 20 and want to know what combinations of 
1,2,3,4 would yield this result? I'm not even sure what this is called 
to be able to look for a solution. Thanks!

Stoopid noob!  ;)
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