ML Programming Lab: Anonymous Functions and Higher-Order Functions, Lab Reports of Computer Science

Download ML Programming Lab: Anonymous Functions and Higher-Order Functions and more Lab Reports Computer Science in PDF only on Docsity! CECS 424 Lab on 9/27/05 Do the following: 1. Start SML for ML programming. 2. Learn to program with anonymous functions and higher order functions in ML. Type each of the following lines and see what happens: a) Anonymous functions i) Note ML’s response to the following two function definitions and function calls fun f x = x + 2; (* defines a named function f *) f 1; fn x => x + 2; (* defines an anonymous function that does the same thing as f *) (fn x => x + 2) 1; ii) (* Example on p.137 quicksort (L,lt) -- Returns a sorted copy of list L, sorted in order of the less-than predicate lt. We use the quicksort algorithm, always choosing the first element of the list as the pivot. *) fun quicksort (nil, lt) = nil | quicksort (pivot::rest, lt) = let (* This function splits a list into two parts: those elements lt pivot and those elements not lt pivot. We return a this pair of lists. *) fun split(nil) = (nil,nil) | split(x::xs) = let val (below, above) = split(xs) in if lt(x,pivot) then (x::below, above) else (below, x::above) end; val (below, above) = split(rest) in quicksort (below, lt) @ [pivot] @ quicksort (above, lt) end; quicksort ([1, 4, 3, 2, 5], fn (a, b) => a < b); (* quicksort is called with an anonymous function *) quicksort ([1, 4, 3, 2, 5], fn (a, b) => a > b); (* quicksort is called with an anonymous function *) quicksort ([1, 4, 3, 2, 5], op <); (* quicksort is called with a predefined operator *) quicksort ([1, 4, 3, 2, 5], op >); (* quicksort is called with a predefined operator *)