A parser for things is a function from strings to lists of pairs of things and strings. Not mine, don't remember where I got it. In this case it's

A parser for things is a function from strings to lists of pairs of things and strings. Not mine, don't remember where I got it. In this case it's Maybe instead of list, which means no implicit backtracking. It's very much the case that in a real parser you'll want to do more with errors and location and such.