Lecture 1: Beginning ML
=======================

1. Hello world in SML

print "Hello world\n";


2. factorial function

C versions:

int fact (int n) {
  int i, result;
  i = 1;
  result = 1;
  while (i <= n) {
     result = result * i;
  }
  return result;
} 

int fact (int n) {
  int i, result;
  result = 1;
  for (i=1; i <= n; i++) {
     result = result * i;
  }
  return result;
} 

And here is a complete program that will take arguments as 
command line options:

-------------
#include <stdio.h>

int fact (int n) {
  int i, result;
  i = 1;
  result = 1;
  while (i <= n) {
     result *= i;
     i++;
  }
  return result;
} 

main (int argc, char *argv[]) {
  int x;
  sscanf(argv[1], "%d$", &x);
  printf("%d\n", fact(x));
  return 0;
}
============

Scheme version

(define fact
    (lambda (n)
      (cond ((= n 0) 1)
            (else (* n (fact (- n 1)))))))

============
ML versions

fun fact1 n = if n = 0 then 1 else n * fact1(n-1);

---------
fun fact2 0 = 1
  | fact2 n = n * fact2 (n-1);

---------
fun range n m = if m < n then [] else n :: range (n+1) m

fun prod [] = 1
  | prod (x::xs) = x * prod xs;

fun fact3 n = prod(range 1 n);

---------
fun fact4 n = foldl (op * ) 1 (range 1 n);


===========
Haskel versions

fact :: Int -> Int

fact 0 = 1
fact n = n * fact (n-1)

---------
fact :: Int -> Int

fact 0 = 1
fact (n+1) = (n+1) * fact n

---------
fact n = product [1 .. n]