# LibTmux.Query.optionalRelated

- **Package:** libtmux-haskell
- **Language:** Haskell
- **Kind:** function
- **Source:** https://github.com/libtmux/libtmux-haskell/blob/663e212622a02aa74a9bdc8ff71e2b45fcb1d4d5/internal/LibTmux/Internal/Query.hs#L215
- **Page:** https://libtmux.org/en/haskell/latest/reference/libtmux-query-v-optionalrelated/

```haskell
optionalRelated
  :: ToOptional row child -> Expr child -> Expr row
```

Signature types: [`ToOptional`](/en/haskell/latest/reference/libtmux-query-t-tooptional/), [`Expr`](/en/haskell/latest/reference/libtmux-query-t-expr/).

Test a known optional target. Absence yields False, so negation includes
 absence as well as targets that fail the child predicate.

## Referenced declarations

- [`LibTmux.Query.Expr`](/en/haskell/latest/reference/libtmux-query-t-expr/) (data type)
- [`LibTmux.Query.ToOptional`](/en/haskell/latest/reference/libtmux-query-t-tooptional/) (data type)

## Guides

Pages that discuss `optionalRelated`.

- [Typed queries](/en/haskell/latest/guides/query/)