initial checkin

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

string/monoid.go

@@ -0,0 +1,8 @@
+package string
+
+import (
+	M "github.com/ibm/fp-go/monoid"
+)
+
+// Monoid is the monoid implementing string concatenation
+var Monoid = M.MakeMonoid(concat, "")

string/monoid_test.go

@@ -0,0 +1,11 @@
+package string
+
+import (
+	"testing"
+
+	M "github.com/ibm/fp-go/monoid/testing"
+)
+
+func TestMonoid(t *testing.T) {
+	M.AssertLaws(t, Monoid)([]string{"", "a", "some value"})
+}

string/semigroup.go

@@ -0,0 +1,15 @@
+package string
+
+import (
+	"fmt"
+
+	S "github.com/ibm/fp-go/semigroup"
+)
+
+func concat(left string, right string) string {
+	return fmt.Sprintf("%s%s", left, right)
+}
+
+func Semigroup() S.Semigroup[string] {
+	return S.MakeSemigroup(concat)
+}

string/string.go

@@ -0,0 +1,49 @@
+package string
+
+import (
+	"strings"
+
+	F "github.com/ibm/fp-go/function"
+	O "github.com/ibm/fp-go/ord"
+)
+
+var (
+	// ToUpperCase converts the string to uppercase
+	ToUpperCase = strings.ToUpper
+
+	// ToLowerCase converts the string to lowercase
+	ToLowerCase = strings.ToLower
+
+	// Ord implements the default ordering for strings
+	Ord = O.FromStrictCompare[string]()
+)
+
+func Eq(left string, right string) bool {
+	return left == right
+}
+
+func ToBytes(s string) []byte {
+	return []byte(s)
+}
+
+func IsEmpty(s string) bool {
+	return len(s) == 0
+}
+
+func IsNonEmpty(s string) bool {
+	return len(s) > 0
+}
+
+func Size(s string) int {
+	return len(s)
+}
+
+// Includes returns a predicate that tests for the existence of the search string
+func Includes(searchString string) func(string) bool {
+	return F.Bind2nd(strings.Contains, searchString)
+}
+
+// Equals returns a predicate that tests if a string is equal
+func Equals(other string) func(string) bool {
+	return F.Bind2nd(Eq, other)
+}

string/string_test.go

@@ -0,0 +1,12 @@
+package string
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestEmpty(t *testing.T) {
+	assert.True(t, IsEmpty(""))
+	assert.False(t, IsEmpty("Carsten"))
+}