Heavily inspired by the Parsec library from Haskell, this library allows you to
use certain operators to emulate fmap like functionality, composing functions with
Parser objects. For instance:
p = str.upper % String("hello world")constructs a parser object that matches the literal text hello world and then returns
the result of applying the str.upper function to it (so 'HELLO WORLD'). It allows
you do chain these together, so here would be a parser for an integer:
integerP = int % Regex(r'[-+]?[0-9]+')
# integerP.parse("-37") --> -37
# integerP.parse("bad") --> None