Example: Concatenate lists a and b

list procedure cat(list a, list b) {    list t = list u = copylist(a);    while (t.tail != nil) t = t.tail;    t.tail = b;    return u; }

In an imperative language

cat(a,b)   if b = nil then a else cons(head(a), cat(tail(a),b))

In a functional language

In a declarative language

cat([], Z, Z). cat([H|T], L, [H|Z]) :- cat(T, L, Z).

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