The only file worth anything is fours.hs
The solve function takes a list of numbers and a single number and returns all the ways that list can be combined with basic arithmetic into that single number.
Input: [1,2,3,4] 10
output:
(1 + 2) + (3 + 4) = 10
(1 * 2 * 3) + 4 = 10
and so on....
Output will always include parenthesis because any expression without parenthesis can be expressed with them as well.
This is actually a pretty dang hard programming challenge, and my favorite. Give it a try if you want to challenge yourself.