Halftones moving operator

doc/cheatsheet.txt

@@ -23,6 +23,11 @@ Arytmetyka
 	(aktualnie brak wsparcia dla precedensji operatorów)
 	3 * (4 * 12 - 8)
 
+Przesuwanie dźwięków o półtony
+	c + 1 == c#
+	c - 1 == b
+	c12 + 1 == d12
+
 Wywołanie funkcji
 	foo 1 2 3
 

src/interpreter.cc

@@ -10,8 +10,8 @@ constexpr auto binary_operator()
 	return [](Interpreter&, std::vector<Value> args) -> Result<Value> {
 		auto result = std::move(args.front());
 		for (auto &v : std::span(args).subspan(1)) {
-			assert(result.type == Value::Type::Number, "LHS should be a number");
+			assert(result.type == Value::Type::Number, "LHS should be a number"); // TODO(assert)
-			assert(v.type == Value::Type::Number,      "RHS should be a number");
+			assert(v.type == Value::Type::Number,      "RHS should be a number"); // TODO(assert)
 			if constexpr (std::is_same_v<Number, std::invoke_result_t<Binary_Operation, Number, Number>>) {
 				result.n = Binary_Operation{}(std::move(result.n), std::move(v).n);
 			} else {
@@ -36,7 +36,7 @@ template<typename Binary_Predicate>
 constexpr auto comparison_operator()
 {
 	return [](Interpreter&, std::vector<Value> args) -> Result<Value> {
-		assert(args.size() == 2, "(in)Equality only allows for 2 operands"); // TODO(assert)
+		assert(args.size() == 2, "Ordering only allows for 2 operands"); // TODO(assert)
 		assert(args.front().type == args.back().type, "Only values of the same type can be ordered"); // TODO(assert)
 
 		switch (args.front().type) {
@@ -118,6 +118,42 @@ static inline Result<void> create_chord(std::vector<Note> &chord, Interpreter &i
 	return {};
 }
 
+/// Creates implementation of plus/minus operator that support following operations:
+///   number, number -> number (standard math operations)
+///   n: number, m: music  -> music
+///   m: music,  n: number -> music  moves m by n semitones (+ goes up, - goes down)
+template<typename Binary_Operation>
+[[gnu::always_inline]]
+static inline auto plus_minus_operator()
+{
+	return [](Interpreter&, std::vector<Value> args) -> Result<Value> {
+		assert(args.size() == 2, "Binary operator only accepts 2 arguments");
+		auto lhs = std::move(args.front());
+		auto rhs = std::move(args.back());
+
+		if (lhs.type == rhs.type && lhs.type == Value::Type::Number) {
+			return Value::from(Binary_Operation{}(std::move(lhs).n, std::move(rhs).n));
+		}
+
+		if (lhs.type == Value::Type::Music && rhs.type == Value::Type::Number) {
+music_number_operation:
+			for (auto &note : lhs.chord.notes) {
+				note.base = Binary_Operation{}(note.base, rhs.n.as_int());
+				note.simplify_inplace();
+			}
+			return lhs;
+		}
+
+		if (lhs.type == Value::Type::Number && rhs.type == Value::Type::Music) {
+			std::swap(lhs, rhs);
+			goto music_number_operation;
+		}
+
+		assert(false, "Unsupported types for this operation"); // TODO(assert)
+		unreachable();
+	};
+}
+
 Interpreter::Interpreter()
 {
 	{ // Context initialization
@@ -189,8 +225,8 @@ Interpreter::Interpreter()
 			return Value::from(std::move(chord));
 		});
 
-		operators["+"] = binary_operator<std::plus<>>();
+		operators["+"] = plus_minus_operator<std::plus<>>();
-		operators["-"] = binary_operator<std::minus<>>();
+		operators["-"] = plus_minus_operator<std::minus<>>();
 		operators["*"] = binary_operator<std::multiplies<>>();
 		operators["/"] = binary_operator<std::divides<>>();
 

src/musique.hh

@@ -472,7 +472,7 @@ struct Block
 struct Note
 {
 	/// Base of a note, like `c` (=0), `c#` (=1) `d` (=2)
-	u8 base;
+	i32 base;
 
 	/// Octave in MIDI acceptable range (from -1 to 9 inclusive)
 	std::optional<i8> octave = std::nullopt;
@@ -490,9 +490,11 @@ struct Note
 	u8 into_midi_note(i8 default_octave) const;
 
 	bool operator==(Note const&) const;
+
+	void simplify_inplace();
 };
 
-std::ostream& operator<<(std::ostream& os, Note const& note);
+std::ostream& operator<<(std::ostream& os, Note note);
 
 struct Chord
 {

src/value.cc

@@ -41,8 +41,15 @@ constexpr u8 note_index(Indexable<usize, char> auto const& note)
 	return -1;
 }
 
-constexpr std::string_view note_index_to_string(u8 note_index)
+#include <iostream>
+
+constexpr std::string_view note_index_to_string(auto note_index)
 {
+	note_index %= 12;
+	if (note_index < 0) {
+		note_index = 12 + note_index;
+	}
+
 	switch (note_index) {
 	case  0:	return "c";
 	case  1:	return "c#";
@@ -178,6 +185,7 @@ Result<Value> Value::operator()(Interpreter &i, std::vector<Value> args)
 				if (args.size() == 2) {
 					note.length = args[1].n;
 				}
+				note.simplify_inplace();
 			}
 
 			return *this;
@@ -380,8 +388,19 @@ u8 Note::into_midi_note(i8 default_octave) const
 	return (octave + 1) * 12 + base;
 }
 
-std::ostream& operator<<(std::ostream& os, Note const& note)
+void Note::simplify_inplace()
 {
+	if (octave) {
+		octave = std::clamp(*octave + int(base / 12), -1, 9);
+		if ((base %= 12) < 0) {
+			base = 12 + base;
+		}
+	}
+}
+
+std::ostream& operator<<(std::ostream& os, Note note)
+{
+	note.simplify_inplace();
 	os << note_index_to_string(note.base);
 	if (note.octave) {
 		os << ":oct=" << int(*note.octave);
@@ -416,13 +435,15 @@ Chord Chord::from(std::string_view source)
 
 std::ostream& operator<<(std::ostream& os, Chord const& chord)
 {
-	os << "chord[";
+	if (chord.notes.size() == 1) {
+		return os << chord.notes.front();
+	}
 
+	os << "chord[";
 	for (auto it = chord.notes.begin(); it != chord.notes.end(); ++it) {
 		os << *it;
 		if (std::next(it) != chord.notes.end())
 			os << "; ";
 	}
-
 	return os << ']';
 }