core!: 1) add negative index get for slices;

cli!: 2) pass named args to script.

cmd/gad/main.go

@@ -519,8 +519,16 @@ func parseFlags(
 
 	flagset.Usage = func() {
 		_, _ = fmt.Fprint(flagset.Output(),
-			"Usage: gad [flags] [Gad script file]\n\n",
-			"If script file is not provided, REPL terminal application is started\n",
+			"Usage: gad [flags] [SCRIPT_FILE [ARGS...]]\n\n",
+			"If script file is not provided, REPL terminal application is started.\n\n",
+			"If script file is provided, pass named params with '--' prefix and named flags with '-' prefix.\n",
+			"  Script example for join arguments:\n\n",
+			"    // usages: 1) SCRIPT.gad a b c (result: a,b,c)\n",
+			"    //         2) SCRIPT.gad a b c --sep + (result: a+b+c)\n",
+			"    //         3) SCRIPT.gad a b c -ln (result: a,b,c\\n)\n",
+			"    //         4) SCRIPT.gad a b c --sep + -ln (result: a+b+c\\n)\n",
+			"    param (*args, sep=\",\", ln=no)\n",
+			"    if !args { return }\n    for i, arg in args[:-1] { print(arg, sep) }\n    print(args[-1])\n    if ln { println() }\n\n",
 			"Use - to read from stdin\n\n",
 			"\nFlags:\n",
 		)
@@ -609,6 +617,9 @@ func (s *Script) execute() error {
 					i++
 					continue
 				}
+			} else if strings.HasPrefix(arg, "-") && len(arg) > 1 {
+				namedArgs[arg[1:]] = gad.Yes
+				continue
 			}
 			newArgs = append(newArgs, gad.Str(arg))
 		}

objects.go

@@ -236,6 +236,9 @@ func (o RawStr) IndexGet(_ *VM, index Object) (Object, error) {
 	switch v := index.(type) {
 	case Int:
 		idx = int(v)
+		if idx < 0 {
+			idx = len(o) + idx
+		}
 	case Uint:
 		idx = int(v)
 	case Char:
@@ -359,6 +362,9 @@ func (o Str) IndexGet(_ *VM, index Object) (Object, error) {
 	switch v := index.(type) {
 	case Int:
 		idx = int(v)
+		if idx < 0 {
+			idx = len(o) + idx
+		}
 	case Uint:
 		idx = int(v)
 	case Char:
@@ -478,6 +484,9 @@ func (o Bytes) IndexSet(_ *VM, index, value Object) error {
 	switch v := index.(type) {
 	case Int:
 		idx = int(v)
+		if idx < 0 {
+			idx = len(o) + idx
+		}
 	case Uint:
 		idx = int(v)
 	default:
@@ -504,6 +513,9 @@ func (o Bytes) IndexGet(_ *VM, index Object) (Object, error) {
 	switch v := index.(type) {
 	case Int:
 		idx = int(v)
+		if idx < 0 {
+			idx = len(o) + idx
+		}
 	case Uint:
 		idx = int(v)
 	default:
@@ -825,15 +837,18 @@ func (o Array) IndexSet(_ *VM, index, value Object) error {
 	switch v := index.(type) {
 	case Int:
 		idx := int(v)
+		if idx < 0 {
+			idx = len(o) + idx
+		}
 		if idx >= 0 && idx < len(o) {
-			o[v] = value
+			o[idx] = value
 			return nil
 		}
 		return ErrIndexOutOfBounds
 	case Uint:
 		idx := int(v)
 		if idx >= 0 && idx < len(o) {
-			o[v] = value
+			o[idx] = value
 			return nil
 		}
 		return ErrIndexOutOfBounds
@@ -846,14 +861,17 @@ func (o Array) IndexGet(_ *VM, index Object) (Object, error) {
 	switch v := index.(type) {
 	case Int:
 		idx := int(v)
+		if idx < 0 {
+			idx = len(o) + idx
+		}
 		if idx >= 0 && idx < len(o) {
-			return o[v], nil
+			return o[idx], nil
 		}
 		return nil, ErrIndexOutOfBounds
 	case Uint:
 		idx := int(v)
 		if idx >= 0 && idx < len(o) {
-			return o[v], nil
+			return o[idx], nil
 		}
 		return nil, ErrIndexOutOfBounds
 	}

vm_test.go

@@ -72,7 +72,7 @@ func TestVMArray(t *testing.T) {
 		expectRun(t, fmt.Sprintf("idx := %d; return %s.(idx)", idx, arrStr),
 			nil, arr[idx])
 	}
-	expectErrIs(t, fmt.Sprintf("%s[%d]", arrStr, -1), nil, ErrIndexOutOfBounds)
+	expectErrIs(t, fmt.Sprintf("%s[%d]", arrStr, -10), nil, ErrIndexOutOfBounds)
 	expectErrIs(t, fmt.Sprintf("%s[%d]", arrStr, arrLen), nil, ErrIndexOutOfBounds)
 
 	// slice operator
@@ -95,6 +95,9 @@ func TestVMArray(t *testing.T) {
 
 	expectRun(t, fmt.Sprintf("return %s[:]", arrStr), nil, arr)
 	expectRun(t, fmt.Sprintf("return %s[%d:%d]", arrStr, 2, 2), nil, Array{})
+	expectRun(t, `return "ab"[1]`, nil, Int('b'))
+	expectRun(t, `return "ab"[-1]`, nil, Int('b'))
+	expectRun(t, `return "ab"[-2]`, nil, Int('a'))
 	expectErrIs(t, fmt.Sprintf("return %s[%d:\"\"]", arrStr, -1), nil, ErrType)
 	expectErrIs(t, fmt.Sprintf("return %s[:%d]", arrStr, arrLen+1), nil, ErrIndexOutOfBounds)
 	expectErrIs(t, fmt.Sprintf("%s[%d:%d]", arrStr, 2, 1), nil, ErrInvalidIndex)