Promela Reference -- len(5)

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

`NAME`
`len` - predefined operator to determine the number of messages stored in a channel.

`SYNTAX`
`len(` varref `)`

`DESCRIPTION`
A predefined unary operator that takes the name of a channel as an operand and returns the number of messages that it currently holds.

`EXAMPLES`

    chan q = [4] of { mtype, short };

    len(q) >  0	/* same as nempty(q) */
    len(q) == 0	/* same as empty(q) */
    len(q) == 4	/* same as full(q) */
    len(q) <  4	/* same as nfull(q) */

`NOTES`
If `len` is used as a condition statement, rather than on the right side of an assignment, it is unexecutable if the channel is empty.

`SEE ALSO`
`empty(5)`, `full(5)`, `nempty(5)`, `nfull(5)`.

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