7.3 Operators
The Assembler supports a number of operators, which are described here. The higher the precedence, the higher the priority. Expressions may be enclosed in parentheses, and such expressions are always evaluated before combined with anything outside the parentheses. The associativity of binary operators indicates the evaluation order of chained operators, left associativity meaning they are evaluated left to right, i.e., 2 - 3 - 4 is (2 - 3) - 4, while right associativity would mean 2-3-4 is 2 - (3 - 4). Some operators are not associative, meaning chaining has no meaning.
The following operators are defined:
| Symbol | Description |
|---|---|
|
! | Logical not |
|
~ | Bitwise Not |
|
- | Unary Minus |
|
* | Multiplication |
|
/ | Division |
|
% | Modulo ( AVR Assembler 2 only) |
|
+ | Addition |
|
- | Subtraction |
|
<< | Shift left |
|
>> | Shift right |
|
< | Less than |
|
<= | Less than or equal |
|
> | Greater than |
|
>= | Greater than or equal |
|
== | Equal |
|
!= | Not equal |
|
& | Bitwise And |
|
^ | Bitwise Xor |
|
| | Bitwise Or |
|
&& | Logical And |
|
|| | Logical Or |
|
? | Conditional operator |
Logical Not
Symbol: !
Description: Unary operator, which returns 1 if the expression was zero, and returns 0 if the expression was nonzero.
Precedence: 14
Associativity: None
Example: ldi r16,!0xf0 ; Load r16 with 0x00
Bitwise Not
Symbol: ~
Description: Unary operator, which returns the input expression with all bits inverted.
Precedence: 14
Associativity: None
Example: ldi r16,~0xf0 ; Load r16 with 0x0f
Unary Minus
Symbol: -
Description: Unary operator, which returns the arithmetic negation of an expression.
Precedence: 14
Associativity: None
Example: ldi r16,-2 ; Load -2(0xfe) in r16
Multiplication
Symbol: *
Description: Binary operator, which returns the product of two expressions.
Precedence: 13
Associativity: Left
Example: ldi r30,label*2 ; Load r30 with label*2
Division
Symbol: /
Description: Binary operator, which returns the integer quotient of the left expression divided by the right expression.
Precedence: 13
Associativity: Left
Example: ldi r30,label/2 ; Load r30 with label/2
Modulo
Symbol: %
Description: Binary operator, which returns the integer remainder of the left expression divided by the right expression.
Precedence: 13
Associativity: Left
Example: ldi r30,label%2 ; Load r30 with label%2
Addition
Symbol: +
Description: Binary operator, which returns the sum of two expressions.
Precedence: 12
Associativity: Left
Example: ldi r30,c1+c2 ; Load r30 with c1+c2
Subtraction
Symbol: -
Description: Binary operator, which returns the left expression minus the right expression.
Precedence: 12
Associativity: Left
Example: ldi r17,c1-c2 ;Load r17 with c1-c2
Shift left
Symbol: <<
Description: Binary operator, which returns the left expression shifted left the number given by the right expression.
Precedence: 11
Associativity: Left
Example: ldi r17,1<<bitmask ;Load r17 with 1 shifted left
bitmask times
Shift right
Symbol: >>
Description: Binary operator, which returns the left expression shifted right the number given by the right expression.
Precedence: 11
Associativity: Left
Example: ldi r17,c1>>c2 ;Load r17 with c1 shifted right c2
times
Less than
Symbol: <
Description: Binary operator, which returns 1 if the signed expression to the left is Less than the signed expression to the right, 0 otherwise.
Precedence: 10
Associativity: None
Example: ori r18,bitmask*(c1<c2)+1 ;Or r18 with an expression
Less or equal
Symbol: <=
Description: Binary operator, which returns 1 if the signed expression to the left is Less than or Equal to the signed expression to the right, 0 otherwise.
Precedence: 10
Associativity: None
Example: ori r18,bitmask*(c1<=c2)+1 ;Or r18 with an expression
Greater than
Symbol: >
Description: Binary operator, which returns 1 if the signed expression to the left is Greater than the signed expression to the right, 0 otherwise.
Precedence: 10
Associativity: None
Example: ori r18,bitmask*(c1>c2)+1 ;Or r18 with an expression
Greater or equal
Symbol: >=
Description: Binary operator, which returns 1 if the signed expression to the left is Greater than or Equal to the signed expression to the right, 0 otherwise.
Precedence: 10
Associativity: None
Example: ori r18,bitmask*(c1>=c2)+1 ;Or r18 with an expression
Equal
Symbol: ==
Description: Binary operator, which returns 1 if the signed expression to the left is Equal to the signed expression to the right, 0 otherwise.
Precedence: 9
Associativity: None
Example: andi r19,bitmask*(c1==c2)+1 ;And r19 with an expression
Not equal
Symbol: !=
Description: Binary operator, which returns 1 if the signed expression to the left is Not Equal to the signed expression to the right, 0 otherwise.
Precedence: 9
Associativity: None
Example: .SET flag=(c1!=c2) ;Set flag to 1 or 0
Bitwise And
Symbol: &
Description: Binary operator, which returns the bitwise And between two expressions.
Precedence: 8
Associativity: Left
Example: ldi r18,high(c1&c2) ;Load r18 with an expression
Bitwise Xor
Symbol: ^
Description: Binary operator, which returns the bitwise Exclusive Or between two expressions.
Precedence: 7
Associativity: Left
Example: ldi r18,low(c1^c2) ;Load r18 with an expression
Bitwise Or
Symbol: |
Description: Binary operator, which returns the bitwise Or between two expressions.
Precedence: 6
Associativity: Left
Example: ldi r18,low(c1|c2) ;Load r18 with an expression
Logical And
Symbol: &&
Description: Binary operator, which returns 1 if the expressions are both nonzero, 0 otherwise.
Precedence: 5
Associativity: Left
Example: ldi r18,low(c1&&c2) ;Load r18 with an expression
Logical Or
Symbol: ||
Description: Binary operator, which returns 1 if one or both of the expressions are nonzero, 0 otherwise.
Precedence: 4
Associativity: Left
Example: ldi r18,low(c1||c2) ;Load r18 with an expression
Conditional operator
Symbol: ? :
Syntax: condition? expression1 : expression2
Description: Ternary operator, which returns expression1 if condition is true, expression2 otherwise.
Precedence: 3
Associativity: None
Example:
ldi r18, a > b? a : b ;Load r18 with the maximum numeric value of a and
b.