LinkedList

// A linked list represented as an abstract data type

class List<T>: {nil, cons(T: first, List<T>: rest)};

// Below are two equivalent definitions of a recursive 'length' function; both compiling to the same Java code.

// 1. Regular function syntax, with a separate definition for each case.

length1(nil) = 0;
length1(cons(first, rest)) = 1 + length1(rest);

// 2. Set-of-functions syntax, with the definitions grouped into an anonymous set of partial functions.

l.length2 = {nil −> 0, cons(first, rest) −> 1 + rest.length2}.get(l);

// The rhs above is equivalent to: l.accept({nil -> 0, cons(first, rest) -> 1 + rest.length}).

// Test
main(String[]: args) = {
    l = cons(1, cons(2, nil));
    assert l.length1 == 2;
    assert l.length2 == 2;
}