Learn ML with Real Code Examples

val count = ref 0
val isDark = ref false

fun updateUI () = (
    print ("Counter: " ^ Int.toString(!count) ^ "\n");
    print ("Theme: " ^ (if !isDark then "Dark" else "Light") ^ "\n")
)

fun increment () = (
    count := !count + 1;
    updateUI ()
)

fun decrement () = (
    count := !count - 1;
    updateUI ()
)

fun reset () = (
    count := 0;
    updateUI ()
)

fun toggleTheme () = (
    isDark := not !isDark;
    updateUI ()
)

(* Simulate actions *)
updateUI ();
increment ();
increment ();
toggleTheme ();
decrement ();
reset ();

Demonstrates a simple counter with theme toggling using ML variables and functions.

fun fib 0 = 0
  | fib 1 = 1
  | fib n = fib(n-1) + fib(n-2)

fun printFib n = 
    if n < 10 then (
        print (Int.toString(fib n) ^ "\n");
        printFib (n+1)
    ) else ()

printFib 0;

Generates the first 10 Fibonacci numbers recursively.

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

val result = fact 5;
print(Int.toString(result) ^ "\n");

Calculates factorial using recursion.

fun isPrime n =
  let
    fun check i = i*i > n orelse (n mod i <> 0 andalso check (i+1))
  in
    if n < 2 then false else check 2
  end;

val n = 13;
print(if isPrime n then "Prime\n" else "Not Prime\n");

Checks if a number is prime.

val lst = [1,2,3,4,5];
fun sum [] = 0
  | sum (x::xs) = x + sum xs;

val result = sum lst;
print(Int.toString(result) ^ "\n");

Calculates the sum of a list.

fun reverseString s =
  let
    fun rev [] acc = acc
      | rev (x::xs) acc = rev xs (x::acc)
  in
    String.implode (rev (String.explode s) [])
  end;

val r = reverseString "HELLO";
print(r ^ "\n");

Reverses a string.

fun table n i = 
    if i > 10 then ()
    else (
        print(Int.toString(n) ^ " x " ^ Int.toString(i) ^ " = " ^ Int.toString(n*i) ^ "\n");
        table n (i+1)
    );

table 5 1;

Prints multiplication table of a number.

val c = 25.0;
val f = (c * 9.0 / 5.0) + 32.0;
print (Real.toString(f) ^ "\n");

Converts Celsius to Fahrenheit.

val temp = 80;
val thresh = 75;
print(if temp > thresh then "Alarm: Temperature Too High!\n" else "Temperature Normal\n");

Simulates an alarm when a threshold is exceeded.

val steps = 10;
val _ = ref 0;
val pos = ref 0;
for i = 1 to steps do (
    if Random.rand() < 0.5 then pos := !pos + 1 else pos := !pos - 1;
    print(Int.toString(!pos) ^ "\n");
);

Simulates a 1D random walk.