Symbol quoting and user defined incoming MIDI message processing

src/interpreter.cc

@@ -609,6 +609,23 @@ error:
 			unreachable();
 		});
 
+		global.force_define("incoming", +[](Interpreter &i, std::vector<Value> args) -> Result<Value> {
+			assert(args.size() == 2, "Wrong arity of 'incoming' function");
+			assert(args[0].type == Value::Type::Symbol, "Expected symbol for first argument of 'incoming'");
+			assert(is_callable(args[1].type), "Expected function for second argument of 'incoming'");
+
+			std::string const& symbol = args[0].s;
+
+			if (symbol == "note_on" || symbol == "noteon") {
+				i.callbacks->note_on = std::move(args[1]);
+			} else if (symbol == "note_off" || symbol == "noteoff") {
+				i.callbacks->note_off = std::move(args[1]);
+			} else {
+				assert(false, "symbol not recognized for 'incoming'");
+			}
+			return Value{};
+		});
+
 		{
 			constexpr auto pgmchange = +[](Interpreter &i, std::vector<Value> args) -> Result<Value> {
 				using Program = Shape<Value::Type::Number>;
@@ -668,6 +685,10 @@ Result<Value> Interpreter::eval(Ast &&ast)
 		switch (ast.token.type) {
 		case Token::Type::Symbol:
 			{
+				if (ast.token.source.starts_with('\'')) {
+					return Value::from(std::move(ast.token.source).substr(1));
+				}
+
 				auto const value = env->find(std::string(ast.token.source));
 				assert(value, "Missing variable error is not implemented yet: variable: "s + std::string(ast.token.source));
 				return *value;

src/unicode.cc

@@ -100,6 +100,11 @@ bool unicode::is_space(u32 space)
 
 bool unicode::is_identifier(u32 letter, unicode::First_Character is_first_character)
 {
-	return (unicode::is_letter(letter) || letter == '_' || letter == '#' || letter == '$' || letter == '@')
+	return (unicode::is_letter(letter)
-	|| (!bool(is_first_character) && (letter == '\'' || unicode::is_digit(letter)));
+		|| letter == '\''
+		|| letter == '_'
+		|| letter == '#'
+		|| letter == '$'
+		|| letter == '@')
+	|| (!bool(is_first_character) && unicode::is_digit(letter));
 }