v0.0.465

langext/array.go

@@ -474,6 +474,17 @@ func ArrAppend[T any](arr []T, add ...T) []T {
 	return r
 }
 
+// ArrPrepend works similar to append(x, y, z) - but doe snot touch the old array and creates a new one
+// Also - in contrast to ArrAppend - the add values are inserted at the start of the resulting array (in reverse order)
+func ArrPrepend[T any](arr []T, add ...T) []T {
+	out := make([]T, len(arr)+len(add))
+	copy(out[len(add):], arr)
+	for i := 0; i < len(add); i++ {
+		out[len(add)-i-1] = add[i]
+	}
+	return out
+}
+
 // ArrCopy does a shallow copy of the 'in' array
 func ArrCopy[T any](in []T) []T {
 	out := make([]T, len(in))

langext/array_test.go

@@ -2,6 +2,7 @@ package langext
 
 import (
 	"gogs.mikescher.com/BlackForestBytes/goext/tst"
+	"strings"
 	"testing"
 )
 
@@ -10,3 +11,13 @@ func TestJoinString(t *testing.T) {
 	res := JoinString(ids, ",")
 	tst.AssertEqual(t, res, "1,2,3")
 }
+
+func TestArrPrepend(t *testing.T) {
+	v1 := []string{"1", "2", "3"}
+
+	v2 := ArrPrepend(v1, "4", "5", "6")
+
+	tst.AssertEqual(t, strings.Join(v1, ""), "123")
+	tst.AssertEqual(t, strings.Join(v2, ""), "654123")
+
+}