backup

input.go

@@ -42,12 +42,12 @@ func (in *Input) Seek(i int) {
 	in.index = i
 }
 
-func (in *Input) Take(amount int) *Input {
+func (in *Input) Take(offset int) *Input {
 	var out = &Input{
 		index: 0,
-		input: in.input[in.index : in.index+amount],
+		input: in.input[in.index : in.index+offset],
 	}
-	in.index += amount
+	in.index += offset
 	return out
 }
 
@@ -70,3 +70,27 @@ func (in *Input) Find(open, close *Token) (int, bool) {
 		return 0, false
 	}
 }
+
+func (in *Input) TakeParens(open, close *Token) (*Input, error) {
+	if in.input[in.index].Equals(open) {
+		return nil, noMatch
+	}
+	start := in.index
+	level := 1
+	idx := slices.IndexFunc(in.input[start+1:], func(a Lexeme) bool {
+		switch {
+		case a.Equals(open):
+			level++
+		case a.Equals(close):
+			level--
+			return level == 0
+		}
+		return false
+	})
+	if idx > -1 {
+		_ = in.Take(idx + 1)
+		return &Input{index: 0, input: in.input[start+1 : idx]}, nil
+	} else {
+		return nil, fmt.Errorf("unmatched parenthesis starting at %s", in.Peek(start).Position())
+	}
+}