# libtmux::exactly_one

- **Module:** libtmux
- **Package:** libtmux-cxx
- **Language:** C++
- **Kind:** function
- **Source:** https://github.com/libtmux/libtmux-cxx/blob/393d4b0ad666f18a6581f1eb281741a75a7503f0/include/libtmux/cardinality.hpp#L62
- **Page:** https://libtmux.org/en/cxx/latest/reference/libtmux-exactly_one/

```
libtmux::exactly_one(Range: ReferenceRange, range: Range &) -> ReferenceRange
```

`exactly_one` states that several is a caller error, and says which one.