scan builtin; Value and Array conviniance constructors made explicit

CHANGELOG.md

@@ -7,6 +7,14 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Added
+
+* Added `scan` builtin, which computes prefix sum of passed values when provided with addition operator
+
+### Fixed
+
+* Prevented accidental recursive construction of Arrays and Values by making convinience constructor `Value::Value(std::vector<Value>&&)` explicit
+
 ## [0.1.0] - 2022-09-25
 
 ### Added

musique/interpreter/builtin_functions.cc

@@ -564,6 +564,28 @@ static Result<Value> builtin_fold(Interpreter &interpreter, std::vector<Value> a
 	return init;
 }
 
+/// Scan computes inclusive prefix sum
+static Result<Value> builtin_scan(Interpreter &interpreter, std::vector<Value> args)
+{
+	if (args.size()) {
+		if (auto p = get_if<Function>(args.front())) {
+			auto xs = Try(flatten(interpreter, std::span(args).subspan(1)));
+			for (auto i = 1u; i < xs.size(); ++i) {
+				xs[i] = Try((*p)(interpreter, { xs[i-1], xs[i] }));
+			}
+			return xs;
+		}
+	}
+
+	return errors::Unsupported_Types_For {
+		.type = errors::Unsupported_Types_For::Function,
+		.name = "scan",
+		.possibilities = {
+			"(callback, ...array) -> any"
+		}
+	};
+}
+
 /// Execute blocks depending on condition
 static Result<Value> builtin_if(Interpreter &i, std::vector<Value> args)  {
 	static constexpr auto guard = Guard<2> {
@@ -997,6 +1019,7 @@ void Interpreter::register_builtin_functions()
 	global.force_define("reverse",        builtin_reverse);
 	global.force_define("rotate",         builtin_rotate);
 	global.force_define("round",          apply_numeric_transform<&Number::round>);
+	global.force_define("scan",           builtin_scan);
 	global.force_define("shuffle",        builtin_shuffle);
 	global.force_define("sim",            builtin_sim);
 	global.force_define("sort",           builtin_sort);

musique/interpreter/builtin_operators.cc

@@ -89,17 +89,16 @@ static Result<Value> plus_minus_operator(Interpreter &interpreter, std::vector<V
 
 		static_assert(std::is_same_v<std::plus<>, Binary_Operation> || std::is_same_v<std::minus<>, Binary_Operation>,
 				"Error message printing only supports operators given above");
-		return Error {
-			.details = errors::Unsupported_Types_For {
-				.type = errors::Unsupported_Types_For::Operator,
-				.name = std::is_same_v<std::plus<>, Binary_Operation> ? "+" : "-",
-				.possibilities = {
-					"(number, number) -> number",
-					"(music, number) -> music",
-					"(number, music) -> music",
-					"(array, number|music) -> array",
-					"(number|music, array) -> array",
-				}
+
+		return errors::Unsupported_Types_For {
+			.type = errors::Unsupported_Types_For::Operator,
+			.name = std::is_same_v<std::plus<>, Binary_Operation> ? "+" : "-",
+			.possibilities = {
+				"(number, number) -> number",
+				"(music, number) -> music",
+				"(number, music) -> music",
+				"(array, number|music) -> array",
+				"(number|music, array) -> array",
 			}
 		};
 	});

musique/value/array.cc

@@ -7,7 +7,7 @@ Array::Array(Array &&)     = default;
 Array::~Array()            = default;
 
 Array::Array(std::vector<Value>&& elements)
-	: elements{std::move(elements)}
+	: elements(std::move(elements))
 {
 }
 

musique/value/array.hh

@@ -15,7 +15,7 @@ struct Array : Collection
 	std::vector<Value> elements;
 
 	Array();
-	Array(std::vector<Value>&&);
+	explicit Array(std::vector<Value>&&);
 	Array(Array const&);
 	Array(Array &&);
 	~Array() override;

musique/value/value.hh

@@ -38,7 +38,7 @@ struct Value
 	Value(char const* s);              ///< Create value of type symbol holding provided symbol
 	Value(std::string s);              ///< Create value of type symbol holding provided symbol
 	Value(std::string_view s);         ///< Create value of type symbol holding provided symbol
-	Value(std::vector<Value> &&array); ///< Create value of type array holding provided array
+	explicit Value(std::vector<Value> &&array); ///< Create value of type array holding provided array
 
 	// TODO Most strings should not be allocated by Value, but reference to string allocated previously
 	// Wrapper for std::string is needed that will allocate only when needed, middle ground between: