Promela Reference -- hidden(2)

### `Promela` | ### `Declarator` | ### `hidden(2)`

`NAME`
`hidden` - for excluding data from the state descriptor during verification.

`SYNTAX`
`hidden` typename ivar

`DESCRIPTION`
The keyword `hidden` can be used to prefix the declaration of any variable, to exclude the value of that variable from the definition of the global system state. The addition of this prefix can affect only the verification process, by potentially changing the outcome of state matching and cycle detection.

`EXAMPLES`

    hidden byte a;
    hidden short p[3];

`NOTES`
The prefix should only be used for write-only scratch variables. The keyword is likely to become obsolete in future versions of Promela, being superseded by the predefined write-only variable `_` (i.e., typed as a single underscore).

It is safe to use `hidden` variables as pseudo local variables inside `atomic` sequences provided that the variables never occur within the guards of an `if` or `do` construct, and provided that there is no reference to the `hidden` variables from outside the `atomic` sequence.

`SEE ALSO`
`datatypes(2)`, `show(2)`, `_(5)`.

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