fix: introduce Kleisli type

Signed-off-by: Dr. Carsten Leue <carsten.leue@de.ibm.com>
2025-11-23 22:14:53 +02:00 · 2025-11-07 14:35:46 +01:00
parent b3bd5e9ad3
commit aa5e908810
90 changed files with 9616 additions and 5168 deletions
--- a/v2/either/bind_test.go
+++ b/v2/either/bind_test.go
@@ -20,6 +20,7 @@ import (

 	F "github.com/IBM/fp-go/v2/function"
 	"github.com/IBM/fp-go/v2/internal/utils"
+	L "github.com/IBM/fp-go/v2/optics/lens"
 	"github.com/stretchr/testify/assert"
 )

@@ -54,3 +55,307 @@ func TestApS(t *testing.T) {

 	assert.Equal(t, res, Of[error]("John Doe"))
 }
+
+// Test types for lens-based operations
+type Counter struct {
+	Value int
+}
+
+type Person struct {
+	Name string
+	Age  int
+}
+
+type Config struct {
+	Debug   bool
+	Timeout int
+}
+
+func TestApSL(t *testing.T) {
+	// Create a lens for the Age field
+	ageLens := L.MakeLens(
+		func(p Person) int { return p.Age },
+		func(p Person, a int) Person { p.Age = a; return p },
+	)
+
+	t.Run("ApSL with Right value", func(t *testing.T) {
+		result := F.Pipe1(
+			Right[error](Person{Name: "Alice", Age: 25}),
+			ApSL(ageLens, Right[error](30)),
+		)
+
+		expected := Right[error](Person{Name: "Alice", Age: 30})
+		assert.Equal(t, expected, result)
+	})
+
+	t.Run("ApSL with Left in context", func(t *testing.T) {
+		result := F.Pipe1(
+			Left[Person](assert.AnError),
+			ApSL(ageLens, Right[error](30)),
+		)
+
+		expected := Left[Person](assert.AnError)
+		assert.Equal(t, expected, result)
+	})
+
+	t.Run("ApSL with Left in value", func(t *testing.T) {
+		result := F.Pipe1(
+			Right[error](Person{Name: "Alice", Age: 25}),
+			ApSL(ageLens, Left[int](assert.AnError)),
+		)
+
+		expected := Left[Person](assert.AnError)
+		assert.Equal(t, expected, result)
+	})
+
+	t.Run("ApSL with both Left", func(t *testing.T) {
+		result := F.Pipe1(
+			Left[Person](assert.AnError),
+			ApSL(ageLens, Left[int](assert.AnError)),
+		)
+
+		expected := Left[Person](assert.AnError)
+		assert.Equal(t, expected, result)
+	})
+}
+
+func TestBindL(t *testing.T) {
+	// Create a lens for the Value field
+	valueLens := L.MakeLens(
+		func(c Counter) int { return c.Value },
+		func(c Counter, v int) Counter { c.Value = v; return c },
+	)
+
+	t.Run("BindL with successful transformation", func(t *testing.T) {
+		// Increment the counter, but fail if it would exceed 100
+		increment := func(v int) Either[error, int] {
+			if v >= 100 {
+				return Left[int](assert.AnError)
+			}
+			return Right[error](v + 1)
+		}
+
+		result := F.Pipe1(
+			Right[error](Counter{Value: 42}),
+			BindL(valueLens, increment),
+		)
+
+		expected := Right[error](Counter{Value: 43})
+		assert.Equal(t, expected, result)
+	})
+
+	t.Run("BindL with failing transformation", func(t *testing.T) {
+		increment := func(v int) Either[error, int] {
+			if v >= 100 {
+				return Left[int](assert.AnError)
+			}
+			return Right[error](v + 1)
+		}
+
+		result := F.Pipe1(
+			Right[error](Counter{Value: 100}),
+			BindL(valueLens, increment),
+		)
+
+		expected := Left[Counter](assert.AnError)
+		assert.Equal(t, expected, result)
+	})
+
+	t.Run("BindL with Left input", func(t *testing.T) {
+		increment := func(v int) Either[error, int] {
+			return Right[error](v + 1)
+		}
+
+		result := F.Pipe1(
+			Left[Counter](assert.AnError),
+			BindL(valueLens, increment),
+		)
+
+		expected := Left[Counter](assert.AnError)
+		assert.Equal(t, expected, result)
+	})
+
+	t.Run("BindL with multiple operations", func(t *testing.T) {
+		double := func(v int) Either[error, int] {
+			return Right[error](v * 2)
+		}
+
+		addTen := func(v int) Either[error, int] {
+			return Right[error](v + 10)
+		}
+
+		result := F.Pipe2(
+			Right[error](Counter{Value: 5}),
+			BindL(valueLens, double),
+			BindL(valueLens, addTen),
+		)
+
+		expected := Right[error](Counter{Value: 20})
+		assert.Equal(t, expected, result)
+	})
+}
+
+func TestLetL(t *testing.T) {
+	// Create a lens for the Value field
+	valueLens := L.MakeLens(
+		func(c Counter) int { return c.Value },
+		func(c Counter, v int) Counter { c.Value = v; return c },
+	)
+
+	t.Run("LetL with pure transformation", func(t *testing.T) {
+		double := func(v int) int { return v * 2 }
+
+		result := F.Pipe1(
+			Right[error](Counter{Value: 21}),
+			LetL[error](valueLens, double),
+		)
+
+		expected := Right[error](Counter{Value: 42})
+		assert.Equal(t, expected, result)
+	})
+
+	t.Run("LetL with Left input", func(t *testing.T) {
+		double := func(v int) int { return v * 2 }
+
+		result := F.Pipe1(
+			Left[Counter](assert.AnError),
+			LetL[error](valueLens, double),
+		)
+
+		expected := Left[Counter](assert.AnError)
+		assert.Equal(t, expected, result)
+	})
+
+	t.Run("LetL with multiple transformations", func(t *testing.T) {
+		double := func(v int) int { return v * 2 }
+		addTen := func(v int) int { return v + 10 }
+
+		result := F.Pipe2(
+			Right[error](Counter{Value: 5}),
+			LetL[error](valueLens, double),
+			LetL[error](valueLens, addTen),
+		)
+
+		expected := Right[error](Counter{Value: 20})
+		assert.Equal(t, expected, result)
+	})
+
+	t.Run("LetL with identity transformation", func(t *testing.T) {
+		identity := func(v int) int { return v }
+
+		result := F.Pipe1(
+			Right[error](Counter{Value: 42}),
+			LetL[error](valueLens, identity),
+		)
+
+		expected := Right[error](Counter{Value: 42})
+		assert.Equal(t, expected, result)
+	})
+}
+
+func TestLetToL(t *testing.T) {
+	// Create a lens for the Debug field
+	debugLens := L.MakeLens(
+		func(c Config) bool { return c.Debug },
+		func(c Config, d bool) Config { c.Debug = d; return c },
+	)
+
+	t.Run("LetToL with constant value", func(t *testing.T) {
+		result := F.Pipe1(
+			Right[error](Config{Debug: true, Timeout: 30}),
+			LetToL[error](debugLens, false),
+		)
+
+		expected := Right[error](Config{Debug: false, Timeout: 30})
+		assert.Equal(t, expected, result)
+	})
+
+	t.Run("LetToL with Left input", func(t *testing.T) {
+		result := F.Pipe1(
+			Left[Config](assert.AnError),
+			LetToL[error](debugLens, false),
+		)
+
+		expected := Left[Config](assert.AnError)
+		assert.Equal(t, expected, result)
+	})
+
+	t.Run("LetToL with multiple fields", func(t *testing.T) {
+		timeoutLens := L.MakeLens(
+			func(c Config) int { return c.Timeout },
+			func(c Config, t int) Config { c.Timeout = t; return c },
+		)
+
+		result := F.Pipe2(
+			Right[error](Config{Debug: true, Timeout: 30}),
+			LetToL[error](debugLens, false),
+			LetToL[error](timeoutLens, 60),
+		)
+
+		expected := Right[error](Config{Debug: false, Timeout: 60})
+		assert.Equal(t, expected, result)
+	})
+
+	t.Run("LetToL setting same value", func(t *testing.T) {
+		result := F.Pipe1(
+			Right[error](Config{Debug: false, Timeout: 30}),
+			LetToL[error](debugLens, false),
+		)
+
+		expected := Right[error](Config{Debug: false, Timeout: 30})
+		assert.Equal(t, expected, result)
+	})
+}
+
+func TestLensOperationsCombined(t *testing.T) {
+	// Test combining different lens operations
+	valueLens := L.MakeLens(
+		func(c Counter) int { return c.Value },
+		func(c Counter, v int) Counter { c.Value = v; return c },
+	)
+
+	t.Run("Combine LetToL and LetL", func(t *testing.T) {
+		double := func(v int) int { return v * 2 }
+
+		result := F.Pipe2(
+			Right[error](Counter{Value: 100}),
+			LetToL[error](valueLens, 10),
+			LetL[error](valueLens, double),
+		)
+
+		expected := Right[error](Counter{Value: 20})
+		assert.Equal(t, expected, result)
+	})
+
+	t.Run("Combine LetL and BindL", func(t *testing.T) {
+		double := func(v int) int { return v * 2 }
+		validate := func(v int) Either[error, int] {
+			if v > 100 {
+				return Left[int](assert.AnError)
+			}
+			return Right[error](v)
+		}
+
+		result := F.Pipe2(
+			Right[error](Counter{Value: 25}),
+			LetL[error](valueLens, double),
+			BindL(valueLens, validate),
+		)
+
+		expected := Right[error](Counter{Value: 50})
+		assert.Equal(t, expected, result)
+	})
+
+	t.Run("Combine ApSL and LetL", func(t *testing.T) {
+		addFive := func(v int) int { return v + 5 }
+
+		result := F.Pipe2(
+			Right[error](Counter{Value: 10}),
+			ApSL(valueLens, Right[error](20)),
+			LetL[error](valueLens, addFive),
+		)
+
+		expected := Right[error](Counter{Value: 25})
+		assert.Equal(t, expected, result)
+	})
+}