Add local variables to Kym

debug/app.ona

@@ -1,6 +1,8 @@
 
+title = "Afterglow"
+
 return {
-    title = "Afterglow",
+    title = title,
     width = 1280,
     height = 800,
     tick_rate = 60,

source/coral/utf8.zig

@@ -172,8 +172,6 @@ pub const HexadecimalFormat = struct {
 		_ = self;
 		_ = writer;
 		_ = value;
-
-		unreachable;
 	}
 };
 
@@ -267,7 +265,8 @@ noinline fn print_value(writer: io.Writer, value: anytype) PrintError!void {
 		.Float => DecimalFormat.default.print(writer, value),
 
 		.Pointer => |pointer| switch (pointer.size) {
-			.One, .Many, .C => HexadecimalFormat.default.print(writer, @intFromPtr(value)),
+			.Many, .C => HexadecimalFormat.default.print(writer, @intFromPtr(value)),
+			.One => if (pointer.child == []const u8) print_string(writer, *value) else HexadecimalFormat.default.print(writer, @intFromPtr(value)),
 			.Slice => if (pointer.child == u8) print_string(writer, value) else @compileError(unformattableMessage(Value)),
 		},
 

source/ona/kym.zig

@@ -30,9 +30,46 @@ const Compiler = struct {
 	state: *State,
 	opcodes: OpcodeList,
 
+	locals: struct {
+		buffer: [255][]const coral.io.Byte = [_][]const coral.io.Byte{""} ** 255,
+		count: u8 = 0,
+
+		const Self = @This();
+
+		fn declare(self: *Self, identifier: []const u8) CompileError!void {
+			if (self.count == self.buffer.len) {
+				return error.TooManyLocals;
+			}
+
+			self.buffer[self.count] = identifier;
+			self.count += 1;
+		}
+
+		fn resolve(self: *Self, local_identifier: []const coral.io.Byte) ?u8 {
+			var index = @as(u8, self.count);
+
+			while (index != 0) {
+				index -= 1;
+
+				if (coral.io.equals(local_identifier, self.buffer[index])) {
+					return index;
+				}
+			}
+
+			return null;
+		}
+	},
+
+	const CompileError = coral.io.AllocationError || error {
+		UndefinedLocal,
+		TooManyLocals,
+	};
+
+	const LocalsList = coral.list.Stack([]const u8);
+
 	const OpcodeList = coral.list.Stack(Opcode);
 
-	fn compile_ast(self: *Compiler, ast: Ast) coral.io.AllocationError!void {
+	fn compile_ast(self: *Compiler, ast: Ast) CompileError!void {
 		for (ast.list_statements()) |statement| {
 			switch (statement) {
 				.return_expression => |return_expression| {
@@ -42,11 +79,21 @@ const Compiler = struct {
 				.return_nothing => {
 					try self.opcodes.push_one(.push_nil);
 				},
+
+				.set_local => |local| {
+					try self.compile_expression(local.expression);
+
+					if (self.locals.resolve(local.identifier)) |index| {
+						try self.opcodes.push_one(.{.set_local = index});
+					} else {
+						try self.locals.declare(local.identifier);
+					}
+				},
 			}
 		}
 	}
 
-	fn compile_expression(self: *Compiler, expression: Ast.Expression) coral.io.AllocationError!void {
+	fn compile_expression(self: *Compiler, expression: Ast.Expression) CompileError!void {
 		const is_zero = struct {
 			fn is_zero(utf8: []const u8) bool {
 				return coral.io.equals(utf8, "0") or coral.io.equals(utf8, "0.0");
@@ -121,7 +168,13 @@ const Compiler = struct {
 
 			.grouped_expression => |grouped_expression| {
 				try self.compile_expression(grouped_expression.*);
-			}
+			},
+
+			.get_local => |local| {
+				try self.opcodes.push_one(.{
+					.get_local = self.locals.resolve(local) orelse return error.UndefinedLocal,
+				});
+			},
 		}
 	}
 
@@ -141,6 +194,7 @@ const Compiler = struct {
 
 	fn make(allocator: coral.io.Allocator, state: *State) Compiler {
 		return .{
+			.locals = .{},
 			.opcodes = OpcodeList.make(allocator),
 			.state = state,
 		};
@@ -190,6 +244,9 @@ pub const Opcode = union (enum) {
 	push_table: u32,
 	push_object: *State.Object,
 
+	set_local: u8,
+	get_local: u8,
+
 	not,
 	neg,
 
@@ -268,6 +325,16 @@ pub const RuntimeEnv = struct {
 					try self.state.push_value(.{.object = acquired_object});
 				},
 
+				.set_local => |local| {
+					if (!self.state.set_value(local, try self.state.pop_value())) {
+						return self.raise(error.BadOperation, "invalid local set");
+					}
+				},
+
+				.get_local => |local| {
+					try self.state.push_value(self.state.get_value(local));
+				},
+
 				.not => {
 					try self.state.push_value(switch (try self.state.pop_value()) {
 						.nil => return self.raise(error.BadOperation, "cannot convert nil to true or false"),
@@ -389,7 +456,11 @@ pub const RuntimeEnv = struct {
 
 		defer compiler.free();
 
-		try compiler.compile_ast(ast);
+		compiler.compile_ast(ast) catch |compile_error| return switch (compile_error) {
+			error.OutOfMemory => error.OutOfMemory,
+			error.UndefinedLocal => self.raise(error.BadOperation, "use of undefined local"),
+			error.TooManyLocals => self.raise(error.OutOfMemory, "functions cannot contain more than 255 locals"),
+		};
 
 		return self.execute_chunk(source.name, compiler.list_opcodes());
 	}

source/ona/kym/Ast.zig

@@ -15,6 +15,7 @@ pub const Expression = union (enum) {
 	string_literal: []const u8,
 	table_literal: NamedList,
 	grouped_expression: *Expression,
+	get_local: []const u8,
 
 	binary_operation: struct {
 		operator: BinaryOperator,
@@ -74,6 +75,11 @@ pub const Statement = union (enum) {
 	return_expression: Expression,
 	return_nothing,
 
+	set_local: struct {
+		identifier: []const coral.io.Byte,
+		expression: Expression,
+	},
+
 	const List = coral.list.Stack(Statement);
 };
 
@@ -175,6 +181,33 @@ pub fn parse(self: *Self, tokenizer: *tokens.Tokenizer) ParseError!void {
 				has_returned = true;
 			},
 
+			.local => |identifier| {
+				try self.check_syntax(tokenizer.step(.{.include_newlines = true}), "statement has no effect");
+
+				switch (tokenizer.current_token) {
+					.symbol_equals => {
+						try self.check_syntax(
+							tokenizer.step(.{.include_newlines = true}),
+							"expected expression after `=`");
+
+						try self.statements.push_one(.{
+							.set_local = .{
+								.identifier = identifier,
+								.expression = try self.parse_expression(tokenizer)
+							}
+						});
+
+						if (tokenizer.step(.{.include_newlines = true})) {
+							try self.check_syntax(
+								tokenizer.current_token == .newline,
+								"expected end of declaration after variable assignment");
+						}
+					},
+
+					else => return self.fail_syntax("expected `=` after local"),
+				}
+			},
+
 			else => return self.fail_syntax("invalid statement"),
 		}
 	}
@@ -211,17 +244,17 @@ fn parse_factor(self: *Self, tokenizer: *tokens.Tokenizer) ParseError!Expression
 		},
 
 		.number => |value| {
-			_ = tokenizer.step(.{.include_newlines = false});
-
 			return Expression{.number_literal = value};
 		},
 
 		.string => |value| {
-			_ = tokenizer.step(.{.include_newlines = false});
-
 			return Expression{.string_literal = value};
 		},
 
+		.local => |identifier| {
+			return Expression{.get_local = identifier};
+		},
+
 		.symbol_brace_left => {
 			try self.check_syntax(tokenizer.step(.{.include_newlines = false}), "unexpected end of table literal");
 
@@ -249,6 +282,8 @@ fn parse_factor(self: *Self, tokenizer: *tokens.Tokenizer) ParseError!Expression
 							.expression = try self.parse_expression(tokenizer),
 						});
 
+						try self.check_syntax(tokenizer.step(.{.include_newlines = false}), "unexpected end of table");
+
 						switch (tokenizer.current_token) {
 							.symbol_comma => _ = tokenizer.step(.{.include_newlines = false}),
 

source/ona/kym/State.zig

@@ -100,6 +100,14 @@ pub fn free(self: *Self) void {
 	self.interned.free();
 }
 
+pub fn get_value(self: *Self, tail_index: usize) Variant {
+	if (tail_index >= self.values.values.len) {
+		return .nil;
+	}
+
+	return self.values.values[self.values.values.len - (1 + tail_index)];
+}
+
 pub fn make(allocator: coral.io.Allocator) Self {
 	return .{
 		.values = DataStack.make(allocator),
@@ -132,3 +140,13 @@ pub fn release(self: *Self, object: *Object) void {
 		self.allocator.deallocate(object);
 	}
 }
+
+pub fn set_value(self: *Self, tail_index: usize, value: Variant) bool {
+	if (tail_index >= self.values.values.len) {
+		return false;
+	}
+
+	self.values.values[self.values.values.len - (1 + tail_index)] = value;
+
+	return true;
+}

source/ona/kym/tokens.zig

@@ -37,6 +37,7 @@ pub const Token = union(enum) {
 	keyword_true,
 	keyword_return,
 	keyword_self,
+	keyword_const,
 
 	pub fn text(self: Token) []const u8 {
 		return switch (self) {
@@ -71,6 +72,7 @@ pub const Token = union(enum) {
 			.number => |literal| literal,
 			.string => |literal| literal,
 
+			.keyword_const => "const",
 			.keyword_nil => "nil",
 			.keyword_false => "false",
 			.keyword_true => "true",
@@ -160,6 +162,12 @@ pub const Tokenizer = struct {
 					coral.debug.assert(identifier.len != 0);
 
 					switch (identifier[0]) {
+						'c' => if (coral.io.ends_with(identifier, "onst")) {
+							self.current_token = .keyword_const;
+
+							return true;
+						},
+
 						'n' => if (coral.io.ends_with(identifier, "il")) {
 							self.current_token = .keyword_nil;