From: Timo Hoepfner <th-dev@...>
Date: 2005-12-07T21:54:34+09:00
Subject: Build array of possible combinations

Hi,

I'm looking for an easy way to convert a string representing a  
boolean expression like

"(a and (b or c) or d"

to an Array of Arrays (representing sets) representing all possible  
valid combinations like:

[["a","b"],["a","c"],["d"]]

Background: I want to build a tree structure, where constraints like  
the one above are attached to the nodes. They describe, which  
combinations of children are allowed and what valid combinations are  
left once one or more children are already selected.
I'm already doing something like that in Java, but supply the list of  
possible combinations by hand, which quickly gets annoying... The  
rest is done via set operations. The actual business logic is similar  
to (pseude code which looks like Ruby from a Ruby-Newbie's POV...):

set=MySet.new [["a","b"],["a","c"],["d"]]

set.remaining_choices_for [] 		--> ["a","b","c","d"]
set.remaining_choices_for ["a"] 	--> ["b","c"]
set.remaining_choices_for ["d"] 	--> []

set.complete_for? ["a"]		--> false
set.complete_for? ["a","b"]	--> true
set.complete_for? ["d"]		--> true

If you can think of a better approach, please tell...


Thanks for your help,

Timo