add color highlighting during token post-processing

src/parser.cpp

@@ -397,4 +397,33 @@ void print_math_vector(const std::vector<Expression::Token>& tv)
 	}
 }
 
+void print_math_vector(const std::vector<Expression::Token>& tv, const std::vector<int>& highlight_locations)
+{
+	int i, l, h, hl;
+	for (i = 0, l = tv.size() - 1, h = 0, hl = highlight_locations.size(); i < l; i++)
+	{
+		if (h < hl && highlight_locations[h] == i)
+		{
+			std::cout << "\033[31m" << *tv[i].to_math_str() << "\033[0m";
+			h++;
+		}
+		else
+		{
+			std::cout << *tv[i].to_math_str();;
+		}
+	}
+
+	if (tv.size())
+	{
+		if (highlight_locations[highlight_locations.size()-1] == tv.size() - 1)
+		{
+			std::cout << "\033[31m" << *tv[tv.size() - 1].to_math_str() << "\033[0m\n";
+		}
+		else
+		{
+			std::cout << *tv[tv.size() - 1].to_math_str() << "\n";
+		}
+	}
+}
+
 }