Generalized Range stream operation

pkg/stream/stream.go

@@ -251,50 +251,16 @@ func FromIterator[E any](it Iterator[E]) Stream[E] {
 	}
 }
 
-// RangeInteger returns a stream of integers in the range [start, end).
+// Range returns a stream that produces elements over a range beginning at `start`, advanced by the `next` function, and ending when `cond` predicate returns false.
 //
 // Example usage:
 //
-//	s := stream.RangeInteger(1, 4)
-//	out := stream.DebugString(s) // "<1, 2, 3>"
-func RangeInteger[E constraint.Integer](start, end E) Stream[E] {
-	return func(yield Consumer[E]) bool {
-		for i := start; i < end; i++ {
-			if !yield(i) {
-				return false
-			}
-		}
-		return true
-	}
-}
-
-// RangeIntegerStep returns a stream of integers in the range [start, end) with the given step size.
-//
-// Example usage:
-//
-//	s := stream.RangeIntegerStep(1, 7, 2)
+//	s := stream.Range(1, pred.LessThanOrEqual(5), mapper.Increment(2))
 //	out := stream.DebugString(s) // "<1, 3, 5>"
-func RangeIntegerStep[E constraint.Integer](start, end, step E) Stream[E] {
+func Range[E any](start E, cond Predicate[E], next Mapper[E, E]) Stream[E] {
 	return func(yield Consumer[E]) bool {
-		for i := start; i < end; i += step {
-			if !yield(i) {
-				return false
-			}
-		}
-		return true
-	}
-}
-
-// RangeFloatStep returns a stream of floats in the range [start, end) with the given step size.
-//
-// Example usage:
-//
-//	s := stream.RangeFloatStep(1.0, 3.0, 0.5)
-//	out := stream.DebugString(s) // "<1.0, 1.5, 2.0, 2.5>"
-func RangeFloatStep[E constraint.Float](start, end, step E) Stream[E] {
-	return func(yield Consumer[E]) bool {
-		for f := start; f < end; f += step {
-			if !yield(f) {
+		for e := start; cond(e); e = next(e) {
+			if !yield(e) {
 				return false
 			}
 		}

pkg/stream/stream_test.go

@@ -11,6 +11,7 @@ import (
 	"github.com/jpfourny/papaya/pkg/mapper"
 	"github.com/jpfourny/papaya/pkg/optional"
 	"github.com/jpfourny/papaya/pkg/pair"
+	"github.com/jpfourny/papaya/pkg/pred"
 )
 
 func TestEmpty(t *testing.T) {
@@ -329,73 +330,27 @@ func TestFromChannelCtx(t *testing.T) {
 	})
 }
 
-func TestRangeInteger(t *testing.T) {
+func TestRange(t *testing.T) {
 	t.Run("empty", func(t *testing.T) {
-		s := RangeInteger(0, 0)
+		s := Range(0, pred.LessThan(0), mapper.Increment(1))
 		got := CollectSlice(s)
 		var want []int
 		assertElementsMatch(t, got, want)
 	})
 
 	t.Run("non-empty", func(t *testing.T) {
-		s := RangeInteger(1, 4)
+		s := Range(1, pred.LessThanOrEqual(5), mapper.Increment(2))
 		got := CollectSlice(s)
-		want := []int{1, 2, 3}
+		want := []int{1, 3, 5}
 		assertElementsMatch(t, got, want)
 	})
 
 	t.Run("limited", func(t *testing.T) {
-		s := RangeInteger(1, 4)
+		s := Range(1, pred.LessThanOrEqual(5), mapper.Increment(2))
 		got := CollectSlice(Limit(s, 2)) // Stops stream after 2 elements.
-		want := []int{1, 2}
-		assertElementsMatch(t, got, want)
-	})
-}
-
-func TestRangeIntegerStep(t *testing.T) {
-	t.Run("empty", func(t *testing.T) {
-		s := RangeIntegerStep(0, 0, 1)
-		got := CollectSlice(s)
-		var want []int
-		assertElementsMatch(t, got, want)
-	})
-
-	t.Run("non-empty", func(t *testing.T) {
-		s := RangeIntegerStep(1, 4, 2)
-		got := CollectSlice(s)
 		want := []int{1, 3}
 		assertElementsMatch(t, got, want)
 	})
-
-	t.Run("limited", func(t *testing.T) {
-		s := RangeIntegerStep(1, 4, 2)
-		got := CollectSlice(Limit(s, 1)) // Stops stream after 1 element.
-		want := []int{1}
-		assertElementsMatch(t, got, want)
-	})
-}
-
-func TestRangeFloatStep(t *testing.T) {
-	t.Run("empty", func(t *testing.T) {
-		s := RangeFloatStep(0.0, 0.0, 1.0)
-		got := CollectSlice(s)
-		var want []float64
-		assertElementsMatch(t, got, want)
-	})
-
-	t.Run("non-empty", func(t *testing.T) {
-		s := RangeFloatStep(1.0, 4.0, 2.0)
-		got := CollectSlice(s)
-		want := []float64{1.0, 3.0}
-		assertElementsMatch(t, got, want)
-	})
-
-	t.Run("limited", func(t *testing.T) {
-		s := RangeFloatStep(1.0, 4.0, 2.0)
-		got := CollectSlice(Limit(s, 1)) // Stops stream after 1 element.
-		want := []float64{1.0}
-		assertElementsMatch(t, got, want)
-	})
 }
 
 func TestUnion(t *testing.T) {