Functional Programming

October 23, 2014

Functional Programming. I have often heard about the difficulty in functional programming. Immutability, pure functions, Monads a few dozen more of things to know to get started.

For my part, I didn’t find it too difficult in getting started in Racket. While Racket doesn’t seem to be as strict as say Haskell, it seems to be rather nice nonetheless and fast! I wrote two simple programs in it, both are simple games so not purely functional (as they have side effects, namely drawing on the screen).

The first one is a simple “Guess the Number” style game. A random value is generated and then the user has to guess it.

#lang racket

(define number (random 100))

(define (win)
  (display "You won the game! In ")
  (display tries)
  (display " tries!\n")

(define (give-hint g)
  (if (> g number)
    (display "You have to go smaller\n")
    (display "You have to go bigger\n")))

(define (try-again g)
  (display "Nope! ")
  (give-hint g)
  (set! tries (add1 tries)))

(define (check-input g)
    (if (= g number)
      ((try-again g)

(define tries 1)
(define (guessing)
  (let ([g (read)])
    (check-input g)))


I refactored it a bit, although that was just to see if it looked better like that.

I am also in the process of writing a simple game where you have to dodge blocks falling down, losing if one hits you. It’s a bit more complicated, but that was to be expected with graphical output.