What is a problem? 

A decision problem is a language. A language is a set of strings. A string is a finite sequence of elements from a finite set.

A function problem is a total function.

Problems motivates algorithms. A problem(heh) with this world, is that almost all algorithm books are based on imperative languages. How can one do some problems in purely functional languages like Haskell effectively, in a functional way?

This motivates me to write a collection of programs to solve classical problems in Haskell.