Given a regular expression, how would I generate all strings that match it?

Question

I\'m using a simple language of only (), |, spaces, and alpha characters.
Given a regular expression like the following:

(hello         


        

Answer 1

When I did my own custom little language, I wrote a parser first. The parser created a structure in memory that represented the text. For this little language, I would create a structure that's something like this:

Node:
  list of string values
  isRequired
  list of child Nodes

When you parse your text, you would get a list of nodes:

   Node1:
      hello, goodbye
      true
      [] (no child nodes)
   Node2:
      world,
      false
      [
        Node3:
           s,
           false
           []
      ]

Once you parse into this structure, you can imagine code that'll generate what you want given that you understand what must be include, and what may be included. The pseudo code would look like this

recursiveGenerate( node_list, parital )
   if ( node_list is null or is empty )
      add partial to an output list
   for the first node
      if ( ! node.isRequired )
         recursiveGenrate( remaining nodes, partial )
      for each value
         recursiveGenerate( child Nodes + remaining nodes, partial + value )

That should populate your list in the way you want.