Added implementation of functional algorithms

(until they are available in the golang standard library...)

internal/algorithms/slices.go

@@ -0,0 +1,73 @@
+// This file is part of arduino-cli.
+//
+// Copyright 2023 ARDUINO SA (http://www.arduino.cc/)
+//
+// This software is released under the GNU General Public License version 3,
+// which covers the main part of arduino-cli.
+// The terms of this license can be found at:
+// https://www.gnu.org/licenses/gpl-3.0.en.html
+//
+// You can be released from the requirements of the above licenses by purchasing
+// a commercial license. Buying such a license is mandatory if you want to
+// modify or otherwise use the software for commercial activities involving the
+// Arduino software without disclosing the source code of your own applications.
+// To purchase a commercial license, send an email to license@arduino.cc.
+
+package f
+
+// Matcher is a function that tests if a given value match a certain criteria.
+type Matcher[T any] func(T) bool
+
+// Reducer is a function that combines two values of the same type and return
+// the combined value.
+type Reducer[T any] func(T, T) T
+
+// Mapper is a function that converts a value of one type to another type.
+type Mapper[T, U any] func(T) U
+
+// Filter takes a slice of type []T and a Matcher[T]. It returns a newly
+// allocated slice containing only those elements of the input slice that
+// satisfy the matcher.
+func Filter[T any](values []T, matcher Matcher[T]) []T {
+	res := []T{}
+	for _, x := range values {
+		if matcher(x) {
+			res = append(res, x)
+		}
+	}
+	return res
+}
+
+// Map applies the Mapper function to each element of the slice and returns
+// a new slice with the results in the same order.
+func Map[T, U any](values []T, mapper Mapper[T, U]) []U {
+	res := []U{}
+	for _, x := range values {
+		res = append(res, mapper(x))
+	}
+	return res
+}
+
+// Reduce applies the Reducer function to all elements of the input values
+// and returns the result.
+func Reduce[T any](values []T, reducer Reducer[T]) T {
+	var result T
+	for _, v := range values {
+		result = reducer(result, v)
+	}
+	return result
+}
+
+// Equals return a Matcher that matches the given value
+func Equals[T comparable](value T) Matcher[T] {
+	return func(x T) bool {
+		return x == value
+	}
+}
+
+// NotEquals return a Matcher that does not match the given value
+func NotEquals[T comparable](value T) Matcher[T] {
+	return func(x T) bool {
+		return x != value
+	}
+}

internal/algorithms/slices_test.go

@@ -0,0 +1,53 @@
+// This file is part of arduino-cli.
+//
+// Copyright 2023 ARDUINO SA (http://www.arduino.cc/)
+//
+// This software is released under the GNU General Public License version 3,
+// which covers the main part of arduino-cli.
+// The terms of this license can be found at:
+// https://www.gnu.org/licenses/gpl-3.0.en.html
+//
+// You can be released from the requirements of the above licenses by purchasing
+// a commercial license. Buying such a license is mandatory if you want to
+// modify or otherwise use the software for commercial activities involving the
+// Arduino software without disclosing the source code of your own applications.
+// To purchase a commercial license, send an email to license@arduino.cc.
+
+package f_test
+
+import (
+	"strings"
+	"testing"
+
+	f "github.com/arduino/arduino-cli/internal/algorithms"
+	"github.com/stretchr/testify/require"
+)
+
+func TestFilter(t *testing.T) {
+	a := []string{"aaa", "bbb", "ccc"}
+	require.Equal(t, []string{"bbb", "ccc"}, f.Filter(a, func(x string) bool { return x > "b" }))
+	b := []int{5, 9, 15, 2, 4, -2}
+	require.Equal(t, []int{5, 9, 15}, f.Filter(b, func(x int) bool { return x > 4 }))
+}
+
+func TestIsEmpty(t *testing.T) {
+	require.True(t, f.Equals(int(0))(0))
+	require.False(t, f.Equals(int(1))(0))
+	require.True(t, f.Equals("")(""))
+	require.False(t, f.Equals("abc")(""))
+	require.False(t, f.NotEquals(int(0))(0))
+	require.True(t, f.NotEquals(int(1))(0))
+	require.False(t, f.NotEquals("")(""))
+	require.True(t, f.NotEquals("abc")(""))
+}
+
+func TestMap(t *testing.T) {
+	value := "hello, world , how are,you? "
+	parts := f.Map(strings.Split(value, ","), strings.TrimSpace)
+
+	require.Equal(t, 4, len(parts))
+	require.Equal(t, "hello", parts[0])
+	require.Equal(t, "world", parts[1])
+	require.Equal(t, "how are", parts[2])
+	require.Equal(t, "you?", parts[3])
+}