Error reporting improvement for number operations; added power operator

include/musique.hh

@@ -184,6 +184,16 @@ namespace errors
 		} type;
 	};
 
+	struct Arithmetic
+	{
+		enum Type
+		{
+			Division_By_Zero,
+			Fractional_Modulo,
+			Unable_To_Calculate_Modular_Multiplicative_Inverse
+		} type;
+	};
+
 	/// Collection of messages that are considered internal and should not be printed to the end user.
 	namespace internal
 	{
@@ -203,6 +213,7 @@ namespace errors
 
 	/// All possible error types
 	using Details = std::variant<
+		Arithmetic,
 		Closing_Token_Without_Opening,
 		Expected_Expression_Separator_Before,
 		Failed_Numeric_Parsing,
@@ -456,7 +467,7 @@ struct Token
 };
 
 static constexpr usize Keywords_Count  =  6;
-static constexpr usize Operators_Count = 15;
+static constexpr usize Operators_Count = 16;
 
 std::string_view type_name(Token::Type type);
 
@@ -703,17 +714,15 @@ struct Number
 	Number& operator-=(Number const& rhs);
 	Number  operator*(Number const& rhs) const;
 	Number& operator*=(Number const& rhs);
-	Number  operator/(Number const& rhs) const;
+	Result<Number> operator/(Number const& rhs) const;
-	Number& operator/=(Number const& rhs);
+	Result<Number> operator%(Number const& rhs) const;
-	Number  operator%(Number const& rhs) const;
-	Number& operator%=(Number const& rhs);
 
 	Number floor() const; ///< Return number rounded down to nearest integer
 	Number ceil()  const; ///< Return number rounded up to nearest integer
 	Number round() const; ///< Return number rounded to nearest integer
 
-	Number inverse()     const; ///< Return number raised to power -1
+	Result<Number> inverse()     const; ///< Return number raised to power -1
-	Number pow(Number n) const; ///< Return number raised to power `n`.
+	Result<Number> pow(Number n) const; ///< Return number raised to power `n`.
 
 	/// Parses source contained by token into a Number instance
 	static Result<Number> from(Token token);

src/builtin_operators.cc

@@ -87,7 +87,6 @@ static Result<Value> plus_minus_operator(Interpreter &interpreter, std::vector<V
 	};
 }
 
-
 template<typename Binary_Operation, char ...Chars>
 static Result<Value> binary_operator(Interpreter& interpreter, std::vector<Value> args)
 {
@@ -97,7 +96,11 @@ static Result<Value> binary_operator(Interpreter& interpreter, std::vector<Value
 
 	if (NN::typecheck(args)) {
 		auto [lhs, rhs] = NN::move_from(args);
-		return Value::from(Binary_Operation{}(lhs, rhs));
+		if constexpr (is_template_v<Result, decltype(Binary_Operation{}(lhs, rhs))>) {
+			return Value::from(Try(Binary_Operation{}(lhs, rhs)));
+		} else {
+			return Value::from(Binary_Operation{}(lhs, rhs));
+		}
 	}
 
 	if (may_be_vectorized(args)) {
@@ -182,6 +185,14 @@ static Result<Value> multiplication_operator(Interpreter &i, std::vector<Value>
 
 using Operator_Entry = std::tuple<char const*, Intrinsic>;
 
+struct pow_operator
+{
+	inline Result<Number> operator()(Number lhs, Number rhs)
+	{
+		return lhs.pow(rhs);
+	}
+};
+
 /// Operators definition table
 static constexpr auto Operators = std::array {
 	Operator_Entry { "+", plus_minus_operator<std::plus<>> },
@@ -189,6 +200,7 @@ static constexpr auto Operators = std::array {
 	Operator_Entry { "*", multiplication_operator },
 	Operator_Entry { "/", binary_operator<std::divides<>, '/'> },
 	Operator_Entry { "%", binary_operator<std::modulus<>, '%'> },
+	Operator_Entry { "**", binary_operator<pow_operator, '*', '*'> },
 
 	Operator_Entry { "<",  comparison_operator<std::less<>> },
 	Operator_Entry { ">",  comparison_operator<std::greater<>> },

src/errors.cc

@@ -146,6 +146,15 @@ std::ostream& operator<<(std::ostream& os, Error const& err)
 		[](errors::Expected_Expression_Separator_Before const&) { return "Missing semicolon"; },
 		[](errors::Literal_As_Identifier const&)                { return "Literal used in place of an identifier"; },
 		[](errors::Out_Of_Range const&)                         { return "Index out of range"; },
+		[](errors::Arithmetic const& err)                       {
+			switch (err.type) {
+			case errors::Arithmetic::Division_By_Zero: return "Division by 0";
+			case errors::Arithmetic::Fractional_Modulo: return "Modulo with fractions";
+			case errors::Arithmetic::Unable_To_Calculate_Modular_Multiplicative_Inverse:
+				return "Missing modular inverse";
+			default: unreachable();
+			}
+		},
 		[](errors::Closing_Token_Without_Opening const& err)    {
 			return err.type == errors::Closing_Token_Without_Opening::Block
 				? "Block closing without opening"
@@ -368,6 +377,32 @@ std::ostream& operator<<(std::ostream& os, Error const& err)
 			print_error_line(loc);
 		},
 
+		[&](errors::Arithmetic const& err) {
+			switch (err.type) {
+			break; case errors::Arithmetic::Division_By_Zero:
+				os << "Tried to divide by 0 which is undefined operation in math\n";
+				os << "\n";
+				print_error_line(loc);
+
+			break; case errors::Arithmetic::Fractional_Modulo:
+				os << "Tried to calculate modulo with fractional modulus which is not defined\n";
+				os << "\n";
+
+				print_error_line(loc);
+
+				os << pretty::begin_comment;
+				os << "Example code that could raise this error:\n";
+				os << "  1 % (1/2)\n";
+				os << pretty::end;
+
+			break; case errors::Arithmetic::Unable_To_Calculate_Modular_Multiplicative_Inverse:
+				os << "Tried to calculate fraction in modular space.\n";
+				os << "\n";
+
+				print_error_line(loc);
+			}
+		},
+
 		[&](errors::Unexpected_Keyword const&)               { unimplemented(); },
 	}, err.details);
 

src/number.cc

@@ -106,37 +106,72 @@ Number& Number::operator*=(Number const& rhs)
    	return *this;
 }
 
-Number Number::operator/(Number const& rhs) const
+Result<Number> Number::operator/(Number const& rhs) const
 {
-  	return Number{num * rhs.den, den * rhs.num}.simplify();
+	if (rhs.num == 0) {
+		return Error {
+			.details = errors::Arithmetic {
+				.type = errors::Arithmetic::Division_By_Zero
+			}
+		};
+	}
+	return Number{num * rhs.den, den * rhs.num}.simplify();
 }
 
-Number& Number::operator/=(Number const& rhs)
+inline auto modular_inverse(Number::value_type a, Number::value_type n)
+	-> Result<Number::value_type>
 {
-   	num *= rhs.den;
+	using N = Number::value_type;
-   	den *= rhs.num;
+	N t = 0, newt = 1;
-   	simplify_inplace();
+	N r = n, newr = a;
-   	return *this;
-}
 
-
+	while (newr != 0) {
-Number  Number::operator%(Number const& rhs) const
+		auto q = r / newr;
-{
+		t = std::exchange(newt, t - q * newt);
-	return Number(*this) %= rhs;
+		r = std::exchange(newr, r - q * newr);
-}
-
-Number& Number::operator%=(Number const& rhs)
-{
-	simplify_inplace();
-	auto [rnum, rden] = rhs.simplify();
-
-	if (den == 1 && rden == 1) {
-		num %= rnum;
-	} else {
-		assert(false, "Modulo for fractions is not supported");
 	}
 
-	return *this;
+	if (r > 1) {
+		return Error {
+			.details = errors::Arithmetic {
+				.type = errors::Arithmetic::Unable_To_Calculate_Modular_Multiplicative_Inverse
+			}
+		};
+	}
+
+	return t < 0 ? t + n : t;
+}
+
+
+Result<Number> Number::operator%(Number const& rhs) const
+{
+	if (rhs.num == 0) {
+		return Error {
+			.details = errors::Arithmetic {
+				.type = errors::Arithmetic::Division_By_Zero
+			}
+		};
+	}
+
+	auto ret = simplify();
+	auto [rnum, rden] = rhs.simplify();
+
+	if (rden != 1) {
+		return Error {
+			.details = errors::Arithmetic {
+				.type = errors::Arithmetic::Fractional_Modulo
+			}
+		};
+	}
+
+	if (ret.den == 1) {
+		ret.num %= rnum;
+		return ret;
+	}
+
+	return Number(
+		(Try(modular_inverse(ret.den, rnum)) * ret.num) % rnum
+	);
 }
 
 std::ostream& operator<<(std::ostream& os, Number const& n)
@@ -252,16 +287,22 @@ Number Number::round() const
 	return impl::round(*this, impl::Rounding_Mode::Round);
 }
 
-Number Number::inverse() const
+Result<Number> Number::inverse() const
 {
-	assert(num != 0, "Cannot take inverse of fraction with 0 in denominator");
+	if (num == 0) {
+		return Error {
+			.details = errors::Arithmetic {
+				.type = errors::Arithmetic::Division_By_Zero
+			}
+		};
+	}
 	return { den, num };
 }
 
 namespace impl
 {
 	// Raise Number to integer power helper
-	static inline Number pow(Number const& x, decltype(Number::num) n)
+	static inline Result<Number> pow(Number const& x, decltype(Number::num) n)
 	{
 		// We simply raise numerator and denominator to required power
 		// and if n is negative we take inverse.
@@ -273,11 +314,11 @@ namespace impl
 
 		for (auto i = n; i != 0; --i) result.num *= x.num;
 		for (auto i = n; i != 0; --i) result.den *= x.den;
-		return flip ? result.inverse() : result;
+		return flip ? Try(result.inverse()) : result;
 	}
 }
 
-Number Number::pow(Number n) const
+Result<Number> Number::pow(Number n) const
 {
 	n.simplify_inplace();
 
@@ -289,9 +330,5 @@ Number Number::pow(Number n) const
 	// Hard case, we raise this to fractional power.
 	// Essentialy finding n.den root of (x to n.num power).
 	// We need to protect ourselfs against even roots of negative numbers.
-	// TODO Implement this case properly.
-	//
-	// TODO(assert) <- taking power is not always doable so this operation
-	//   should produce error not crash with assertion failure in the future.
 	unimplemented();
 }

src/parser.cc

@@ -519,13 +519,14 @@ static usize precedense(std::string_view op)
 	//  '.' since it have own precedense rules and is not binary expression but its own kind of expression
 	//
 	//  Exclusion of them is marked by subtracting total number of excluded operators.
-	static_assert(Operators_Count - 1 == 14, "Ensure that all operators have defined precedense below");
+	static_assert(Operators_Count - 1 == 15, "Ensure that all operators have defined precedense below");
 
 	if (one_of(op, "or")) return 100;
 	if (one_of(op, "and")) return 150;
 	if (one_of(op, "<", ">", "<=", ">=", "==", "!=")) return 200;
 	if (one_of(op, "+", "-")) return 300;
 	if (one_of(op, "*", "/", "%", "&")) return 400;
+	if (one_of(op, "**")) return 500;
 
 	unreachable();
 }