Pair

README.md

@@ -33,6 +33,7 @@ Fp-go is a collection of Functional Programming helpers powered by Golang [1.18]
   - [Curry](#curry)
 - [Structs](#structs)
   - [Option](#option)
+  - [Pair](#pair)
 
 ## Install
 
@@ -243,3 +244,10 @@ Option represents encapsulation of an optional value, it might be used as the re
 You could instanciate an `opt.Option[T]` with a value with `opt.Some(val)`. If the value is missing you can use `opt.None[T]()`.
 
 Option exports `Some`, `None`, `IsSome`, `IsNone`, `GetOrElse`, `Match`, `Map`, `Chain`.
+
+
+#### Pair
+
+Pair allows you to group 2 values into a single struct. Can be used to make a function with multiple returns return a sigle wrapped value
+
+Pair exports `New`, `Fst`, `Snd`, `Get`, `MapFst`, `MapSnd`, `MapBoth`, `CheckFst`, `CheckSnd`, `CheckBoth`, `Merge`, `MergeC`, `Eq`, `Zip`.

pair/pair.go

@@ -0,0 +1,105 @@
+package pair
+
+// Base Pair struct
+type Pair[A, B any] struct {
+	a A
+	b B
+}
+
+// Constructor for a Pair
+func New[A, B any](a A, b B) Pair[A, B] {
+	return Pair[A, B]{a, b}
+}
+
+// Getter for the first value of the Pair
+func Fst[A, B any](t Pair[A, B]) A {
+	return t.a
+}
+
+// Getter for the second value of the Pair
+func Snd[A, B any](t Pair[A, B]) B {
+	return t.b
+}
+
+// Getter for both values of the Pair
+func Get[A, B any](t Pair[A, B]) (A, B) {
+	return t.a, t.b
+}
+
+// Execute the function on the first value of the Pair
+func MapFst[B, A, R any](fn func(A) R) func(Pair[A, B]) Pair[R, B] {
+	return func(t Pair[A, B]) Pair[R, B] {
+		return Pair[R, B]{fn(t.a), t.b}
+	}
+}
+
+// Execute the function on the second value of the Pair
+func MapSnd[A, B, R any](fn func(B) R) func(Pair[A, B]) Pair[A, R] {
+	return func(t Pair[A, B]) Pair[A, R] {
+		return Pair[A, R]{t.a, fn(t.b)}
+	}
+}
+
+// Execute the functions on both the first and second values of the Pair
+func MapBoth[A, B, R, S any](fnF func(A) R, fnS func(B) S) func(Pair[A, B]) Pair[R, S] {
+	return func(t Pair[A, B]) Pair[R, S] {
+		return Pair[R, S]{fnF(t.a), fnS(t.b)}
+	}
+}
+
+// Helper to chcek if the first value of the Pair satisfies a predicate
+func CheckFst[B, A any](fn func(A) bool) func(Pair[A, B]) bool {
+	return func(t Pair[A, B]) bool {
+		return fn(t.a)
+	}
+}
+
+// Helper to chcek if the second value of the Pair satisfies a predicate
+func CheckSnd[A, B any](fn func(B) bool) func(Pair[A, B]) bool {
+	return func(t Pair[A, B]) bool {
+		return fn(t.b)
+	}
+}
+
+// Helper to chcek if both the first and the second values of the Pair satisfies their respective predicate
+func CheckBoth[A, B any](fnF func(A) bool, fnS func(B) bool) func(Pair[A, B]) bool {
+	return func(t Pair[A, B]) bool {
+		return fnF(t.a) && fnS(t.b)
+	}
+}
+
+// Merge the elements of a Pair with a Curried function
+func MergeC[A, B, C any](fn func(A) func(B) C) func(Pair[A, B]) C {
+	return func(t Pair[A, B]) C {
+		return fn(t.a)(t.b)
+	}
+}
+
+// Merge the elements of a Pair with a non-Curried function
+func Merge[A, B, C any](fn func(A, B) C) func(Pair[A, B]) C {
+	return func(t Pair[A, B]) C {
+		return fn(t.a, t.b)
+	}
+}
+
+// Check two Pairs for element-by-element equality. The types must be comparable
+func Eq[A, B comparable](p1 Pair[A, B]) func(Pair[A, B]) bool {
+	return func(p2 Pair[A, B]) bool {
+		return p1.a == p2.a && p1.b == p2.b
+	}
+}
+
+// Take 2 lists of A and B and merge them into a single list of Pair[A, B]
+// If the lists don't have the same size, the final list will have the same size as the smaller one
+func Zip[B, A any](lstA []A) func([]B) []Pair[A, B] {
+	return func(lstB []B) (res []Pair[A, B]) {
+		i := 0
+
+		for i < len(lstA) && i < len(lstB) {
+			res = append(res, New(lstA[i], lstB[i]))
+			i++
+		}
+
+		return
+	}
+}

pair/pair_test.go

@@ -0,0 +1,227 @@
+package pair
+
+import "testing"
+
+func eq[A, B comparable](ps1, ps2 []Pair[A, B]) bool {
+	if len(ps1) != len(ps2) {
+		return false
+	}
+
+	for i := 0; i < len(ps1); i++ {
+		if !Eq(ps1[i])(ps2[i]) {
+			return false
+		}
+	}
+
+	return true
+}
+
+func TestNew(t *testing.T) {
+	res := New(42, "42")
+	if res.a != 42 {
+		t.Error("New should return a struct with 42 as the first value. Received:", res.a)
+	}
+	if res.b != "42" {
+		t.Error("New should return a struct with \"42\" as the second value. Received:", res.b)
+	}
+}
+
+func TestFst(t *testing.T) {
+	res := Fst(New(42, "42"))
+	if res != 42 {
+		t.Error("Fst should return 42. Received:", res)
+	}
+}
+
+func TestSnd(t *testing.T) {
+	res := Snd(New(42, "42"))
+	if res != "42" {
+		t.Error("Fst should return \"42\". Received:", res)
+	}
+}
+
+func TestGet(t *testing.T) {
+	res1, res2 := Get(New(42, "42"))
+	if res1 != 42 {
+		t.Error("Get should return 42 as the first value. Received:", res1)
+	}
+	if res2 != "42" {
+		t.Error("Get should return \"42\" as the second value. Received:", res2)
+	}
+}
+
+func TestMapFst(t *testing.T) {
+	res := MapFst[string](func(x int) int { return x + 1 })(New(41, "42"))
+	if Fst(res) != 42 {
+		t.Error("MapFirst should return 42 as a first value. Received:", Fst(res))
+	}
+	if Snd(res) != "42" {
+		t.Error("MapFst should leave the second value \"42\" alone. Received:", Snd(res))
+	}
+}
+
+func TestMapSnd(t *testing.T) {
+	res := MapSnd[string](func(x int) int { return x + 1 })(New("42", 41))
+	if Fst(res) != "42" {
+		t.Error("MapSnd should leave the first value \"42\" alone. Received:", Fst(res))
+	}
+	if Snd(res) != 42 {
+		t.Error("MapFirst should return 42 as a second value. Received:", Snd(res))
+	}
+}
+
+func TestMapBoth(t *testing.T) {
+	res := MapBoth(
+		func(x bool) bool { return !x },
+		func(x int) int { return x + 1 },
+	)(New(false, 41))
+
+	if Fst(res) != true {
+		t.Error("MapBoth should return true as the first value. Received:", Fst(res))
+	}
+	if Snd(res) != 42 {
+		t.Error("MapBoth should return 42 as the second value. Received:", Snd(res))
+	}
+}
+
+func TestCheckFst_True(t *testing.T) {
+	res := CheckFst[string](func(x int) bool { return x > 10 })(New(42, "42"))
+	if res != true {
+		t.Error("CheckFst should return true. Received:", res)
+	}
+}
+
+func TestCheckFst_False(t *testing.T) {
+	res := CheckFst[string](func(x int) bool { return x < 10 })(New(42, "42"))
+	if res != false {
+		t.Error("CheckFst should return false. Received:", res)
+	}
+}
+
+func TestCheckSnd_True(t *testing.T) {
+	res := CheckSnd[int](func(x string) bool { return x == "42" })(New(42, "42"))
+	if res != true {
+		t.Error("CheckFst should return true. Received:", res)
+	}
+}
+
+func TestCheckSnd_False(t *testing.T) {
+	res := CheckSnd[int](func(x string) bool { return x == "1" })(New(42, "42"))
+	if res != false {
+		t.Error("CheckFst should return false. Received:", res)
+	}
+}
+
+func TestCheckBoth_True_True(t *testing.T) {
+	res := CheckBoth(
+		func(x int) bool { return x > 10 },
+		func(x string) bool { return x == "42" },
+	)(New(42, "42"))
+
+	if res != true {
+		t.Error("CheckBoth should return true. Received:", res)
+	}
+}
+
+func TestCheckBoth_True_False(t *testing.T) {
+	res := CheckBoth(
+		func(x int) bool { return x > 10 },
+		func(x string) bool { return x != "42" },
+	)(New(42, "42"))
+
+	if res != false {
+		t.Error("CheckBoth should return false. Received:", res)
+	}
+}
+
+func TestCheckBoth_False_True(t *testing.T) {
+	res := CheckBoth(
+		func(x int) bool { return x < 10 },
+		func(x string) bool { return x == "42" },
+	)(New(42, "42"))
+
+	if res != false {
+		t.Error("CheckBoth should return false. Received:", res)
+	}
+}
+
+func TestCheckBoth_False_False(t *testing.T) {
+	res := CheckBoth(
+		func(x int) bool { return x < 10 },
+		func(x string) bool { return x != "42" },
+	)(New(42, "42"))
+
+	if res != false {
+		t.Error("CheckBoth should return false. Received:", res)
+	}
+}
+
+func TestMergeC(t *testing.T) {
+	mul := func(a int) func(int) int { return func(b int) int { return a * b } }
+
+	res := MergeC(mul)(New(21, 2))
+	if res != 42 {
+		t.Error("MergeC should return 42. Received:", res)
+	}
+}
+
+func TestMerge(t *testing.T) {
+	mul := func(a, b int) int { return a * b }
+
+	res := Merge(mul)(New(21, 2))
+	if res != 42 {
+		t.Error("Merge should return 42. Received:", res)
+	}
+}
+
+func TestZip_EqLen(t *testing.T) {
+	res := Zip[bool]([]int{1, 2, 3, 4, 5})([]bool{true, true, false, false, true})
+	want := []Pair[int, bool]{New(1, true), New(2, true), New(3, false), New(4, false), New(5, true)}
+	if !eq(res, want) {
+		t.Error("Zip should have returned", want, ". Received:", res)
+	}
+}
+
+func TestZip_Large_Fst(t *testing.T) {
+	res := Zip[bool]([]int{1, 2, 3, 4, 5})([]bool{true, true, false})
+	want := []Pair[int, bool]{New(1, true), New(2, true), New(3, false)}
+	if !eq(res, want) {
+		t.Error("Zip should have returned", want, ". Received:", res)
+	}
+}
+
+func TestZip_Large_Snd(t *testing.T) {
+	res := Zip[bool]([]int{1, 2, 3})([]bool{true, true, false, false, true})
+	want := []Pair[int, bool]{New(1, true), New(2, true), New(3, false)}
+	if !eq(res, want) {
+		t.Error("Zip should have returned", want, ". Received:", res)
+	}
+}
+
+func TestEq_True_True(t *testing.T) {
+	res := Eq(New(42, 21))(New(42, 21))
+	if res != true {
+		t.Error("Eq should return true. Received:", res)
+	}
+}
+
+func TestEq_True_False(t *testing.T) {
+	res := Eq(New(42, 21))(New(42, 100))
+	if res != false {
+		t.Error("Eq should return false. Received:", res)
+	}
+}
+
+func TestEq_False_True(t *testing.T) {
+	res := Eq(New(21, 42))(New(100, 42))
+	if res != false {
+		t.Error("Eq should return false. Received:", res)
+	}
+}
+
+func TestEq_False_False(t *testing.T) {
+	res := Eq(New(42, 21))(New(84, 42))
+	if res != false {
+		t.Error("Eq should return false. Received:", res)
+	}
+}