limit :
A limiting operator for xreal-typed signals.
The limit primitive produces a bounded range of output by limiting the input signal in to the range specified by the parameters upper_limit and lower_limit. In other words, the output signal out is set according to the following equation:
out = lower_limit for in < lower_limit in for lower_limit <= in < upper_limit upper_limit for in >= upper_limit 
To pose the lower limit only, the parameter upper_limit can be set to `INFINITY. Similarly, the pose the upper limit only, the parameter lower_limit can be set to -`INFINITY.
Input/Output Terminals
| Name | I/O | Type | Description | 
| out | output | xreal | output signal | 
| in | input | xreal | input signal | 
Parameters
| Name | Type | Default | Unit | Description | 
| upper_limit | real | 1.0 | None | upper-limit level | 
| lower_limit | real | -1.0 | None | lower-limit level |