fn: add predicate combinators for && and ||

fn/predicate.go

@@ -0,0 +1,20 @@
+package fn
+
+// Pred[A] is a type alias for a predicate operating over type A.
+type Pred[A any] func(A) bool
+
+// PredAnd is a lifted version of the && operation that operates over functions
+// producing a boolean value from some type A.
+func PredAnd[A any](p0 Pred[A], p1 Pred[A]) Pred[A] {
+	return func(a A) bool {
+		return p0(a) && p1(a)
+	}
+}
+
+// PredOr is a lifted version of the || operation that operates over functions
+// producing a boolean value from some type A.
+func PredOr[A any](p0 Pred[A], p1 Pred[A]) Pred[A] {
+	return func(a A) bool {
+		return p0(a) || p1(a)
+	}
+}