Appendix B: Operators and Symbols
This appendix includes a glossary of Cairo's syntax.
Operators
Table B-1 contains the operators in Cairo, an example of how the operator would appear in context, a short explanation, and whether that operator is overloadable. If an operator is overloadable, the relevant trait to use to overload that operator is listed.
Table B-1: Operators
| Operator | Example | Explanation | Overloadable? |
|---|---|---|---|
! | !expr | Bitwise or logical complement | Not |
!= | expr != expr | Non-equality comparison | PartialEq |
% | expr % expr | Arithmetic remainder | Rem |
%= | var %= expr | Arithmetic remainder and assignment | RemEq |
& | expr & expr | Bitwise AND | BitAnd |
&& | expr && expr | Short-circuiting logical AND | |
* | expr * expr | Arithmetic multiplication | Mul |
*= | var *= expr | Arithmetic multiplication and assignment | MulEq |
@ | @var | Snapshot | |
* | *var | Desnap | |
+ | expr + expr | Arithmetic addition | Add |
+= | var += expr | Arithmetic addition and assignment | AddEq |
, | expr, expr | Argument and element separator | |
- | -expr | Arithmetic negation | Neg |
- | expr - expr | Arithmetic subtraction | Sub |
-= | var -= expr | Arithmetic subtraction and assignment | SubEq |
-> | fn(...) -> type, |...| -> type | Function and closure return type | |
. | expr.ident | Member access | |
/ | expr / expr | Arithmetic division | Div |
/= | var /= expr | Arithmetic division and assignment | DivEq |
: | pat: type, ident: type | Constraints | |
: | ident: expr | Struct field initializer | |
; | expr; | Statement and item terminator | |
< | expr < expr | Less than comparison | PartialOrd |
<= | expr <= expr | Less than or equal to comparison | PartialOrd |
= | var = expr | Assignment | |
== | expr == expr | Equality comparison | PartialEq |
=> | pat => expr | Part of match arm syntax | |
> | expr > expr | Greater than comparison | PartialOrd |
>= | expr >= expr | Greater than or equal to comparison | PartialOrd |
^ | expr ^ expr | Bitwise exclusive OR | BitXor |
| | expr | expr | Bitwise OR | BitOr |
|| | expr || expr | Short-circuiting logical OR |
Non Operator Symbols
The following list contains all symbols that are not used as operators; that is, they do not have the same behavior as a function or method call.
Table B-2 shows symbols that appear on their own and are valid in a variety of locations.
Table B-2: Stand-Alone Syntax
| Symbol | Explanation |
|---|---|
..._u8, ..._usize, etc. | Numeric literal of specific type |
'...' | Short string |
_ | “Ignored” pattern binding; also used to make integer literals readable |
Table B-3 shows symbols that are used within the context of a module hierarchy path to access an item.
Table B-3: Path-Related Syntax
| Symbol | Explanation |
|---|---|
ident::ident | Namespace path |
super::path | Path relative to the parent of the current module |
trait::method(...) | Disambiguating a method call by naming the trait that defines it |
Table B-4 shows symbols that appear in the context of using generic type parameters.
Table B-4: Generics
| Symbol | Explanation |
|---|---|
path<...> | Specifies parameters to generic type in a type (e.g., Vec<u8>) |
path::<...>, method::<...> | Specifies parameters to generic type, function, or method in an expression; often referred to as turbofish |
fn ident<...> ... | Define generic function |
struct ident<...> ... | Define generic structure |
enum ident<...> ... | Define generic enumeration |
impl<...> ... | Define generic implementation |
Table B-5 shows symbols that appear in the context of calling or defining macros and specifying attributes on an item.
Table B-5: Macros and Attributes
| Symbol | Explanation |
|---|---|
#[meta] | Outer attribute |
Table B-6 shows symbols that create comments.
Table B-6: Comments
| Symbol | Explanation |
|---|---|
// | Line comment |
Table B-7 shows symbols that appear in the context of using tuples.
Table B-7: Tuples
| Symbol | Explanation |
|---|---|
() | Empty tuple (aka unit), both literal and type |
(expr) | Parenthesized expression |
(expr,) | Single-element tuple expression |
(type,) | Single-element tuple type |
(expr, ...) | Tuple expression |
(type, ...) | Tuple type |
expr(expr, ...) | Function call expression; also used to initialize tuple structs and tuple enum variants |
Table B-8 shows the contexts in which curly braces are used.
Table B-8: Curly Brackets
| Context | Explanation |
|---|---|
{...} | Block expression |
Type {...} | struct literal |