initial checkin

Signed-off-by: Dr. Carsten Leue <carsten.leue@de.ibm.com>

eq/eq.go

@@ -0,0 +1,43 @@
+package eq
+
+import (
+	F "github.com/ibm/fp-go/function"
+)
+
+type Eq[T any] interface {
+	Equals(x, y T) bool
+}
+
+type eq[T any] struct {
+	c func(x, y T) bool
+}
+
+func (self eq[T]) Equals(x, y T) bool {
+	return self.c(x, y)
+}
+
+func strictEq[A comparable](a, b A) bool {
+	return a == b
+}
+
+// FromStrictEquals constructs an `Eq` from the canonical comparison function
+func FromStrictEquals[T comparable]() Eq[T] {
+	return FromEquals(strictEq[T])
+}
+
+// FromEquals constructs an `Eq` from the comparison function
+func FromEquals[T any](c func(x, y T) bool) Eq[T] {
+	return eq[T]{c: c}
+}
+
+// Empty returns the equals predicate that is always true
+func Empty[T any]() Eq[T] {
+	return FromEquals(F.Constant2[T, T](true))
+}
+
+// Equals returns a predicate to test if one value equals the other under an equals predicate
+func Equals[T any](eq Eq[T]) func(T) func(T) bool {
+	return func(other T) func(T) bool {
+		return F.Bind2nd(eq.Equals, other)
+	}
+}