(isPrefix.1) isPrefix([], B) = true (isPrefix.2) isPrefix(A, []) = false (when A is not []) (isPrefix.3) isPrefix(h1:t1, h2:t2) = h1 == h2 and isPrefix(t1, t2)Evaluation is as follows.
isPrefix([2,3], [2]) = isPrefix(2:[3], 2:[]) = 2 == 2 and isPrefix([3], []) by (isPrefix.3) = true and isPrefix([3], []) = isPrefix([3], []) = isPrefix(3:[], []) = false by (isPrefix.2)