From e3164395decdc11090c8d4669d7840b6879ccd12 Mon Sep 17 00:00:00 2001
From: Robert Bendun <rob.bendun@gmail.com>
Date: Sun, 21 Aug 2022 13:45:34 +0200
Subject: [PATCH] Range function for Musique language

---
 include/musique.hh       |  5 +++++
 src/builtin_functions.cc | 42 +++++++++++++++++++++++++++++++++++++++-
 2 files changed, 46 insertions(+), 1 deletion(-)

diff --git a/include/musique.hh b/include/musique.hh
index df85dca..2fa938c 100644
--- a/include/musique.hh
+++ b/include/musique.hh
@@ -1023,6 +1023,11 @@ struct Shape
 	static inline auto move_from(std::vector<Value>& args)       { return ::move_from<Types...>(args); }
 	static inline auto typecheck(std::vector<Value>& args)       { return ::typecheck(args, Types...); }
 	static inline auto typecheck_front(std::vector<Value>& args) { return ::typecheck_front(args, Types...); }
+
+	static inline auto typecheck_and_move(std::vector<Value>& args)
+	{
+		return typecheck(args) ? std::optional { move_from(args) } : std::nullopt;
+	}
 };
 
 /// Returns if type can be indexed
diff --git a/src/builtin_functions.cc b/src/builtin_functions.cc
index 277afdf..1926e39 100644
--- a/src/builtin_functions.cc
+++ b/src/builtin_functions.cc
@@ -173,6 +173,42 @@ invalid_argument_type:
 	};
 }
 
+enum class Range_Direction { Up, Down };
+template<Range_Direction dir>
+Result<Value> builtin_range(Interpreter&, std::vector<Value> args)
+{
+	using N   = Shape<Value::Type::Number>;
+	using NN  = Shape<Value::Type::Number, Value::Type::Number>;
+	using NNN = Shape<Value::Type::Number, Value::Type::Number, Value::Type::Number>;
+
+	auto start = Number(0), stop = Number(0), step = Number(1);
+
+	if (0) {}
+	else if (auto a = N::typecheck_and_move(args))   { std::tie(stop)              = *a; }
+	else if (auto a = NN::typecheck_and_move(args))  { std::tie(start, stop)       = *a; }
+	else if (auto a = NNN::typecheck_and_move(args)) { std::tie(start, stop, step) = *a; }
+	else {
+		return Error {
+			.details = errors::Unsupported_Types_For {
+				.type = errors::Unsupported_Types_For::Function,
+				.name = "range",
+				.possibilities = {
+					"(stop: number) -> array of number",
+					"(start: number, stop: number) -> array of number",
+					"(start: number, stop: number, step: number) -> array of number",
+				}
+			},
+			.location = {}
+		};
+	}
+
+	Array array;
+	for (; start < stop; start += step) {
+		array.elements.push_back(Value::from(start));
+	}
+	return Value::from(std::move(array));
+}
+
 void Interpreter::register_builtin_functions()
 {
 	auto &global = *Env::global;
@@ -462,7 +498,7 @@ error:
 			return Error {
 				.details = errors::Unsupported_Types_For {
 					.type = errors::Unsupported_Types_For::Function,
-					.name = "note_off",
+					.name = "program_change",
 					.possibilities = {
 						"(number) -> nil",
 						"(number, number) -> nil",
@@ -480,4 +516,8 @@ error:
 	global.force_define("ceil",  apply_numeric_transform<&Number::ceil>);
 	global.force_define("floor", apply_numeric_transform<&Number::floor>);
 	global.force_define("round", apply_numeric_transform<&Number::round>);
+
+	global.force_define("range", builtin_range<Range_Direction::Up>);
+	global.force_define("up",    builtin_range<Range_Direction::Up>);
+	global.force_define("down",  builtin_range<Range_Direction::Down>);
 }