Operators

Arithmetic Operators

Operator	Meaning	Operand Types	Result Type
+	Addition	int, int	int
+	String concatenation	str, str	str
-	Subtraction	int, int	int
*	Multiplication	int, int	int
/	Division (truncates toward zero)	int, int	int
%	Remainder	int, int	int

The + operator works as addition for integers and concatenation for strings. The behavior is determined by the left operand's type. Mixing types (e.g., int + str) or using bool operands with + causes a runtime error.

flowchart TD
    Start --> A[println 10 + 3]
    A --> B[println 10 - 3]
    B --> C[println 10 * 3]
    C --> D[println 10 / 3]
    D --> E[println 10 % 3]
    E --> F[println 'Hello, ' + 'World!']
    F --> End

$ merx run arith.mmd
13
7
30
3
1
Hello, World!

INFO

• Division by zero causes a runtime error.
• Addition, subtraction, and multiplication wrap around on overflow.
• The % operator follows Rust semantics: -10 % 3 == -1.

Comparison Operators

Operator	Meaning	Operand Types	Result Type
<	Less than	int, int	bool
<=	Less than or equal	int, int	bool
>	Greater than	int, int	bool
>=	Greater than or equal	int, int	bool

Equality Operators

Operator	Meaning	Operand Types	Result Type
==	Equal	any	bool
!=	Not equal	any	bool

Comparing values of different types always results in false for == and true for !=.

Logical Operators

Operator	Meaning	Operand Types	Result Type
&&	Logical AND	bool, bool	bool
||	Logical OR	bool, bool	bool

WARNING

Both sides are always evaluated. There is no short-circuit evaluation.

Unary Operators

Operator	Meaning	Operand Type	Result Type
-	Arithmetic negation	int	int
!	Logical NOT	bool	bool

Unary operators can be chained: --x, !!b.

Operator Precedence

Operators are listed from highest to lowest precedence. Operators at the same level are left-associative.

Precedence	Operators	Description
1 (highest)	- (unary), !	Unary operators
2	as	Type cast
3	*, /, %	Multiplication, division, remainder
4	+, -	Addition, subtraction
5	<, <=, >, >=	Comparison
6	==, !=	Equality
7	&&	Logical AND
8 (lowest)	||	Logical OR

Use parentheses () to override precedence.