Added Map combinator

gigaparsec.go

@@ -191,3 +191,18 @@ func Try[In, Out any](p Parser[In, Out]) Parser[In, Out] {
 		return consumed, reply, err
 	}
 }
+
+func Map[In, Out1, Out2 any](p Parser[In, Out1], f func(Out1) Out2) Parser[In, Out2] {
+	return func(input State[In]) (bool, Result[In, Out2], error) {
+		consumed, reply, err := p(input)
+		if err != nil {
+			return consumed, Result[In, Out2]{}, err
+		}
+		reply2 := Result[In, Out2]{
+			Value:   f(reply.Value),
+			State:   reply.State,
+			Message: reply.Message,
+		}
+		return consumed, reply2, nil
+	}
+}