Mutual recursion: Difference between revisions

=={{header|Standard ML}}==

<lang sml>fun f 0 = 1

| f n = n - m (f (n-1))

and m 0 = 0

| m n = n - f (m (n-1))

;</lang>

The <code>'''fun'''</code> construct creates recursive functions, and the <code>'''and'''</code> allows a group of functions to call each other. The above is just a shortcut for the following:

<lang sml>val rec f = fn 0 => 1

| n => n - m (f (n-1))

and m = fn 0 => 0

| n => n - f (m (n-1))

;</lang>

which indicates that the functions call themselves (<code>'''rec'''</code>) and each other (<code>'''and'''</code>).