# ||= operator

Source: https://ref.dm-lang.org/operator/vertvertequals
Added in BYOND 514.

### Format
> `A ||= B`

### Returns
> Value of `(A || B)` after it has been assigned to A. This expression can stand by itself; its result does not need to be assigned to anything else.

First A is evaluated. If its value is false, B will be evaluated and assigned to A. If A is true, B will not be evaluated and A will remain unchanged.

Note that this is slightly different from `if(!A) A = B` if A is a complex expression such as `list[index++]`, because the expression is only evaluated once.

This operator cannot be overloaded.

### See also
- [|| operator](https://ref.dm-lang.org/operator/vertvert.md)
- [&& operator](https://ref.dm-lang.org/operator/ampamp.md)
- [&&= operator](https://ref.dm-lang.org/operator/ampampequals.md)
- [operators](https://ref.dm-lang.org/operator/index.md)