Promela Reference -- nempty(5)

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

`NAME`
`nempty` - predefined unary operator to test emptiness of a channel.

`SYNTAX`
`nempty(` varref `)`

`DESCRIPTION`
The expression `nempty(q) ,` with `q` a channel name, is equivalent to `len(q) != 0 .` The Promela grammar prohibits this from being written as `!empty(q) .`

Using `nempty` instead of its equivalents can preserve the validity of an addition partial order reduction during verifications, that can be defined with `xr` or `xs` declarations.

`SEE ALSO`
`xr(2)`, `xs(2)`, `empty(5)`, `full(5)`, `len(5)`, `nfull(5)`.

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