Overloaded operators

src/interpreter.cc

@@ -2,7 +2,7 @@
 
 #include <iostream>
 
-static auto binary_operator(auto binop)
+constexpr auto binary_operator(auto binop)
 {
 	return [binop = std::move(binop)](Interpreter&, std::vector<Value> args) -> Result<Value> {
 		auto result = std::move(args.front());
@@ -20,6 +20,34 @@ static auto binary_operator(auto binop)
 	};
 }
 
+constexpr auto equality_operator(auto binop)
+{
+	return [binop = std::move(binop)](Interpreter&, std::vector<Value> args) -> Result<Value> {
+		assert(args.size() == 2, "(in)Equality only allows for 2 operands"); // TODO(assert)
+		return Value::boolean(binop(std::move(args.front()), std::move(args.back())));
+	};
+}
+
+constexpr auto comparison_operator(auto binop)
+{
+	return [binop = std::move(binop)](Interpreter&, std::vector<Value> args) -> Result<Value> {
+		assert(args.size() == 2, "(in)Equality 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) {
+		case Value::Type::Number:
+			return Value::boolean(binop(std::move(args.front()).n, std::move(args.back()).n));
+
+		case Value::Type::Bool:
+			return Value::boolean(binop(std::move(args.front()).b, std::move(args.back()).b));
+
+		default:
+			assert(false, "Cannot compare value of given types"); // TODO(assert)
+		}
+		unreachable();
+	};
+}
+
 Interpreter::Interpreter()
 	: Interpreter(std::cout)
 {
@@ -69,12 +97,13 @@ Interpreter::Interpreter(std::ostream& out)
 	operators["*"] = binary_operator(std::multiplies<>{});
 	operators["/"] = binary_operator(std::divides<>{});
 
-	operators["<"]  = binary_operator(std::less<>{});
+	operators["<"]  = comparison_operator(std::less<>{});
-	operators[">"]  = binary_operator(std::greater<>{});
+	operators[">"]  = comparison_operator(std::greater<>{});
-	operators["<="] = binary_operator(std::less_equal<>{});
+	operators["<="] = comparison_operator(std::less_equal<>{});
-	operators[">="] = binary_operator(std::greater_equal<>{});
+	operators[">="] = comparison_operator(std::greater_equal<>{});
-	operators["=="] = binary_operator(std::equal_to<>{});
+
-	operators["!="] = binary_operator(std::not_equal_to<>{});
+	operators["=="] = equality_operator(std::equal_to<>{});
+	operators["!="] = equality_operator(std::not_equal_to<>{});
 }
 
 Result<Value> Interpreter::eval(Ast &&ast)
@@ -161,6 +190,7 @@ Result<Value> Interpreter::eval(Ast &&ast)
 		unimplemented();
 	}
 }
+
 void Interpreter::enter_scope()
 {
 	env = env->enter();

src/tests/interpreter.cc

@@ -19,7 +19,7 @@ void evaluates_to(Value value, std::string_view source_code, reflection::source_
 	capture_errors([=]() -> Result<void> {
 		Interpreter interpreter;
 		auto result = Try(interpreter.eval(Try(Parser::parse(source_code, "test"))));
-		expect(eq(result, value));
+		expect(eq(result, value), sl);
 		return {};
 	}, sl)();
 }
@@ -38,9 +38,10 @@ void produces_output(std::string_view source_code, std::string_view expected_out
 suite intepreter_test = [] {
 	"Interpreter"_test = [] {
 		should("evaluate literals") = [] {
-			evaluates_to(Value{}, "nil");
+			evaluates_to(Value::boolean(false),     "false");
+			evaluates_to(Value::boolean(true),      "true");
 			evaluates_to(Value::number(Number(10)), "10");
-			// evaluates_to(Value::symbol("notexistingsymbol"), "notexistingsymbol");
+			evaluates_to(Value{},                   "nil");
 		};
 
 		should("evaluate arithmetic") = [] {
@@ -60,6 +61,8 @@ suite intepreter_test = [] {
 		};
 
 		should("allows only for calling which is callable") = [] {
+			evaluates_to(Value::number(Number(0)), "[i|i] 0");
+			{
 				Interpreter i;
 				{
 					auto result = Parser::parse("10 20", "test").and_then([&](Ast &&ast) { return i.eval(std::move(ast)); });
@@ -72,6 +75,34 @@ suite intepreter_test = [] {
 					expect(!result.has_value()) << "Expected code to have failed";
 					expect(eq(result.error().type, errors::Not_Callable));
 				}
+			}
+		};
+
+		should("allow for value (in)equality comparisons") = [] {
+			evaluates_to(Value::boolean(true),  "nil == nil");
+			evaluates_to(Value::boolean(false), "nil != nil");
+
+			evaluates_to(Value::boolean(true),  "true == true");
+			evaluates_to(Value::boolean(false), "true != true");
+			evaluates_to(Value::boolean(false), "true == false");
+			evaluates_to(Value::boolean(true),  "true != false");
+
+			evaluates_to(Value::boolean(true),  "0 == 0");
+			evaluates_to(Value::boolean(false), "0 != 0");
+			evaluates_to(Value::boolean(true),  "1 != 0");
+			evaluates_to(Value::boolean(false), "1 == 0");
+		};
+
+		should("allow for value ordering comparisons") = [] {
+			evaluates_to(Value::boolean(false), "true <  true");
+			evaluates_to(Value::boolean(true),  "true <= true");
+			evaluates_to(Value::boolean(true),  "false < true");
+			evaluates_to(Value::boolean(false), "false > true");
+
+			evaluates_to(Value::boolean(false), "0 <  0");
+			evaluates_to(Value::boolean(true),  "0 <= 0");
+			evaluates_to(Value::boolean(true),  "1 <  2");
+			evaluates_to(Value::boolean(false), "1 >  2");
 		};
 
 		// Added to explicitly test against bug that was in old implementation of enviroments.