homogenous-product.go

/*

UnApply2 is like contra-map function for data type T that unwrap product type
*/  
type UnApply2[T, A, B any] func(T) (A, B)

/*

ProductEq2 is a container, product of type trait instances.
Here, the implementation is a shortcut due to the absence of heterogeneous lists in Golang. 
*/
type ProductEq2[T, A, B any] struct {
  Eq1 Eq[A]
  Eq2 Eq[B]
  UnApply2[T, A, B]
}

// implementation of Eq type class for the product
func (eq ProductEq2[T, A, B]) Equal(a, b T) bool {
  a0, a1 := eq.UnApply2(a)
  b0, b1 := eq.UnApply2(b)
  return eq.Eq1.Equal(a0, b0) && eq.Eq2.Equal(a1, b1)
}