fix: add helpers for reflect types

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

iterator/stateless/generic/reflect.go

@@ -0,0 +1,53 @@
+// Copyright (c) 2023 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 generic
+
+import (
+	R "reflect"
+
+	F "github.com/IBM/fp-go/function"
+	LG "github.com/IBM/fp-go/io/generic"
+	L "github.com/IBM/fp-go/lazy"
+	N "github.com/IBM/fp-go/number"
+	I "github.com/IBM/fp-go/number/integer"
+	O "github.com/IBM/fp-go/option"
+	T "github.com/IBM/fp-go/tuple"
+)
+
+func FromReflect[GR ~func() O.Option[T.Tuple2[GR, R.Value]]](val R.Value) GR {
+	// recursive callback
+	var recurse func(idx int) GR
+
+	// limits the index
+	fromPred := O.FromPredicate(I.Between(0, val.Len()))
+
+	recurse = func(idx int) GR {
+		return F.Pipe3(
+			idx,
+			L.Of[int],
+			L.Map(fromPred),
+			LG.Map[L.Lazy[O.Option[int]], GR](O.Map(
+				F.Flow2(
+					T.Replicate2[int],
+					T.Map2(F.Flow2(N.Add(1), recurse), val.Index),
+				),
+			)),
+		)
+	}
+
+	// start the recursion
+	return recurse(0)
+}

iterator/stateless/reflect.go

@@ -0,0 +1,27 @@
+// Copyright (c) 2023 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 stateless
+
+import (
+	R "reflect"
+
+	G "github.com/IBM/fp-go/iterator/stateless/generic"
+)
+
+// FromReflect creates an iterator that can iterate over types that define [R.Index] and [R.Len]
+func FromReflect(val R.Value) Iterator[R.Value] {
+	return G.FromReflect[Iterator[R.Value]](val)
+}

iterator/stateless/reflect_test.go

@@ -0,0 +1,38 @@
+// Copyright (c) 2023 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 stateless
+
+import (
+	"reflect"
+	"testing"
+
+	A "github.com/IBM/fp-go/array"
+	F "github.com/IBM/fp-go/function"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestReflect(t *testing.T) {
+	ar := A.From("a", "b", "c")
+
+	res := F.Pipe3(
+		reflect.ValueOf(ar),
+		FromReflect,
+		ToArray[reflect.Value],
+		A.Map(reflect.Value.String),
+	)
+
+	assert.Equal(t, ar, res)
+}

reflect/generic/reflect.go

@@ -0,0 +1,31 @@
+// Copyright (c) 2023 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 generic
+
+import (
+	R "reflect"
+)
+
+func Map[GA ~[]A, A any](f func(R.Value) A) func(R.Value) GA {
+	return func(val R.Value) GA {
+		l := val.Len()
+		res := make(GA, l)
+		for i := l - 1; i >= 0; i-- {
+			res[i] = f(val.Index(i))
+		}
+		return res
+	}
+}

reflect/reflect.go

@@ -0,0 +1,42 @@
+// Copyright (c) 2023 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 option
+
+import (
+	R "reflect"
+
+	F "github.com/IBM/fp-go/function"
+	G "github.com/IBM/fp-go/reflect/generic"
+)
+
+func ReduceWithIndex[A any](f func(int, A, R.Value) A, initial A) func(R.Value) A {
+	return func(val R.Value) A {
+		count := val.Len()
+		current := initial
+		for i := 0; i < count; i++ {
+			current = f(i, current, val.Index(i))
+		}
+		return current
+	}
+}
+
+func Reduce[A any](f func(A, R.Value) A, initial A) func(R.Value) A {
+	return ReduceWithIndex(F.Ignore1of3[int](f), initial)
+}
+
+func Map[A any](f func(R.Value) A) func(R.Value) []A {
+	return G.Map[[]A](f)
+}