fix: refactory tests a bit

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

pair/pair.go

@@ -0,0 +1,204 @@
+// Copyright (c) 2024 IBM Corp.
+// All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package pair
+
+import (
+	"fmt"
+
+	F "github.com/IBM/fp-go/function"
+	Sg "github.com/IBM/fp-go/semigroup"
+	T "github.com/IBM/fp-go/tuple"
+)
+
+type (
+	pair struct {
+		head, Tail any
+	}
+
+	// Pair defines a data structure that holds two strongly typed values
+	Pair[A, B any] pair
+)
+
+// String prints some debug info for the object
+//
+// go:noinline
+func pairString(s *pair) string {
+	return fmt.Sprintf("Pair[%T, %t](%v, %v)", s.head, s.Tail, s.head, s.Tail)
+}
+
+// Format prints some debug info for the object
+//
+// go:noinline
+func pairFormat(e *pair, f fmt.State, c rune) {
+	switch c {
+	case 's':
+		fmt.Fprint(f, pairString(e))
+	default:
+		fmt.Fprint(f, pairString(e))
+	}
+}
+
+// String prints some debug info for the object
+func (s Pair[A, B]) String() string {
+	return pairString((*pair)(&s))
+}
+
+// Format prints some debug info for the object
+func (s Pair[A, B]) Format(f fmt.State, c rune) {
+	pairFormat((*pair)(&s), f, c)
+}
+
+// Of creates a [Pair] with the same value to to both fields
+func Of[A any](value A) Pair[A, A] {
+	return Pair[A, A]{head: value, Tail: value}
+}
+
+// FromTuple creates a [Pair] from a [T.Tuple2]
+func FromTuple[A, B any](t T.Tuple2[A, B]) Pair[A, B] {
+	return Pair[A, B]{head: t.F1, Tail: t.F2}
+}
+
+// ToTuple creates a [T.Tuple2] from a [Pair]
+func ToTuple[A, B any](t Pair[A, B]) T.Tuple2[A, B] {
+	return T.MakeTuple2(Head(t), Tail(t))
+}
+
+// MakePair creates a [Pair] from two values
+func MakePair[A, B any](a A, b B) Pair[A, B] {
+	return Pair[A, B]{head: a, Tail: b}
+}
+
+// Head returns the head value of the pair
+func Head[A, B any](fa Pair[A, B]) A {
+	return fa.head.(A)
+}
+
+// Tail returns the head value of the pair
+func Tail[A, B any](fa Pair[A, B]) B {
+	return fa.Tail.(B)
+}
+
+// MonadMapHead maps the head value
+func MonadMapHead[B, A, A1 any](fa Pair[A, B], f func(A) A1) Pair[A1, B] {
+	return Pair[A1, B]{f(Head(fa)), fa.Tail}
+}
+
+// MonadMap maps the head value
+func MonadMap[B, A, A1 any](fa Pair[A, B], f func(A) A1) Pair[A1, B] {
+	return MonadMapHead(fa, f)
+}
+
+// MonadMapTail maps the Tail value
+func MonadMapTail[A, B, B1 any](fa Pair[A, B], f func(B) B1) Pair[A, B1] {
+	return Pair[A, B1]{fa.head, f(Tail(fa))}
+}
+
+// MonadBiMap maps both values
+func MonadBiMap[A, B, A1, B1 any](fa Pair[A, B], f func(A) A1, g func(B) B1) Pair[A1, B1] {
+	return Pair[A1, B1]{f(Head(fa)), g(Tail(fa))}
+}
+
+// Map maps the head value
+func Map[B, A, A1 any](f func(A) A1) func(Pair[A, B]) Pair[A1, B] {
+	return MapHead[B, A, A1](f)
+}
+
+// MapHead maps the head value
+func MapHead[B, A, A1 any](f func(A) A1) func(Pair[A, B]) Pair[A1, B] {
+	return F.Bind2nd(MonadMapHead[B, A, A1], f)
+}
+
+// MapTail maps the Tail value
+func MapTail[A, B, B1 any](f func(B) B1) func(Pair[A, B]) Pair[A, B1] {
+	return F.Bind2nd(MonadMapTail[A, B, B1], f)
+}
+
+// BiMap maps both values
+func BiMap[A, B, A1, B1 any](f func(A) A1, g func(B) B1) func(Pair[A, B]) Pair[A1, B1] {
+	return func(fa Pair[A, B]) Pair[A1, B1] {
+		return MonadBiMap(fa, f, g)
+	}
+}
+
+// MonadChainHead chains on the head value
+func MonadChainHead[B, A, A1 any](sg Sg.Semigroup[B], fa Pair[A, B], f func(A) Pair[A1, B]) Pair[A1, B] {
+	fb := f(Head(fa))
+	return Pair[A1, B]{fb.head, sg.Concat(Tail(fa), Tail(fb))}
+}
+
+// MonadChainTail chains on the Tail value
+func MonadChainTail[A, B, B1 any](sg Sg.Semigroup[A], fb Pair[A, B], f func(B) Pair[A, B1]) Pair[A, B1] {
+	fa := f(Tail(fb))
+	return Pair[A, B1]{sg.Concat(Head(fb), Head(fa)), fa.Tail}
+}
+
+// MonadChain chains on the head value
+func MonadChain[B, A, A1 any](sg Sg.Semigroup[B], fa Pair[A, B], f func(A) Pair[A1, B]) Pair[A1, B] {
+	return MonadChainHead(sg, fa, f)
+}
+
+// ChainHead chains on the head value
+func ChainHead[B, A, A1 any](sg Sg.Semigroup[B], f func(A) Pair[A1, B]) func(Pair[A, B]) Pair[A1, B] {
+	return func(fa Pair[A, B]) Pair[A1, B] {
+		return MonadChainHead(sg, fa, f)
+	}
+}
+
+// ChainTail chains on the Tail value
+func ChainTail[A, B, B1 any](sg Sg.Semigroup[A], f func(B) Pair[A, B1]) func(Pair[A, B]) Pair[A, B1] {
+	return func(fa Pair[A, B]) Pair[A, B1] {
+		return MonadChainTail(sg, fa, f)
+	}
+}
+
+// Chain chains on the head value
+func Chain[B, A, A1 any](sg Sg.Semigroup[B], f func(A) Pair[A1, B]) func(Pair[A, B]) Pair[A1, B] {
+	return ChainHead[B, A, A1](sg, f)
+}
+
+// MonadApHead applies on the head value
+func MonadApHead[B, A, A1 any](sg Sg.Semigroup[B], faa Pair[func(A) A1, B], fa Pair[A, B]) Pair[A1, B] {
+	return Pair[A1, B]{Head(faa)(Head(fa)), sg.Concat(Tail(fa), Tail(faa))}
+}
+
+// MonadApTail applies on the Tail value
+func MonadApTail[A, B, B1 any](sg Sg.Semigroup[A], fbb Pair[A, func(B) B1], fb Pair[A, B]) Pair[A, B1] {
+	return Pair[A, B1]{sg.Concat(Head(fb), Head(fbb)), Tail(fbb)(Tail(fb))}
+}
+
+// MonadAp applies on the head value
+func MonadAp[B, A, A1 any](sg Sg.Semigroup[B], faa Pair[func(A) A1, B], fa Pair[A, B]) Pair[A1, B] {
+	return MonadApHead(sg, faa, fa)
+}
+
+// ApHead applies on the head value
+func ApHead[B, A, A1 any](sg Sg.Semigroup[B], fa Pair[A, B]) func(Pair[func(A) A1, B]) Pair[A1, B] {
+	return func(faa Pair[func(A) A1, B]) Pair[A1, B] {
+		return MonadApHead(sg, faa, fa)
+	}
+}
+
+// ApTail applies on the Tail value
+func ApTail[A, B, B1 any](sg Sg.Semigroup[A], fb Pair[A, B]) func(Pair[A, func(B) B1]) Pair[A, B1] {
+	return func(fbb Pair[A, func(B) B1]) Pair[A, B1] {
+		return MonadApTail(sg, fbb, fb)
+	}
+}
+
+// Ap applies on the head value
+func Ap[B, A, A1 any](sg Sg.Semigroup[B], fa Pair[A, B]) func(Pair[func(A) A1, B]) Pair[A1, B] {
+	return ApHead[B, A, A1](sg, fa)
+}