teaching machines

CS 330 Lecture 23 – Functions in Haskell

April 1, 2016 by Chris Johnson. Filed under cs330, lectures, spring 2016.

Agenda

• what ?s
• what we mean by functional
  • functions are first-class
  • immutability
  • expressions everywhere
• functions in Haskell
• coping with looplessness
• guards to case statements to pattern matching

TODO

• Watch Erik Meijer discuss list comprehensions in both Haskell and Microsoft’s LINQ in the video below. On a 1/4 sheet, generate 3 interesting lists using Haskell’s list comprehensions.

Note

Today we dig deeper into functional programming using the Haskell language. We’ll write a handful of functions together, learn to deal with looplessness, and see some syntactic sugar called pattern matching that tends to make functions short and elegant.

Code

functions.hs

import Data.Char

initialize :: String -> String -> String -> String
-- initialize first middle last = head first : (head middle : (head last : []))
initialize first middle last = head first : head middle : head last : []

initialize' first middle last = [f, m, l]
  where
    f = head first
    m = head middle
    l = head last

capitalize :: String -> String
capitalize s = 
  if s == "" then
    ""
  else
    toUpper (head s) : capitalize (tail s)