Promela Reference -- _last(5)

### `Promela` | ### `Predefined` | ### `_last(5)`

`NAME`
`_last` - predefined global read-only variable.

`SYNTAX`
`_last`

`DESCRIPTION`
`_last` is a predefined global variable that holds the instantiation number of the process that performed the last step in the current execution sequence. The initial value of `_last` is zero. The variable can only be referenced inside `never` claim declarations. It is an error to assign any value to it directly.

`EXAMPLES`

    never {
    	/* it is/is not possible for the process with _pid 1
    	 * to execute every other step forever
    	 */
    accept:	do
    	:: _last != 1 -> _last == 1
    	od
    }

`NOTES`
During verifications this variable is not part of the state descriptor unless it is referred to at least once in the verification model. The additional state information present in this variable can cause an increase of the number of reachable states.

`SEE ALSO`
`_pid(5)` `_(5)`

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