Function isErr

isErr<R extends UnknownTernaryResult>(result: R): result is NarrowToErr<R>
Type guard for the Err variant.
Type Parameters
- R extends UnknownTernaryResult
Parameters
- result: R
Returns result is NarrowToErr<R>
Example
```
const maybeErr = TernaryResult.err('boom') as TernaryResult<
  number,
  string,
  string
>;

if (TernaryResult.isErr(maybeErr)) {
  assert.strictEqual(maybeErr.value, 'boom');
}
```
- Defined in src/functional/ternary-result/impl/ternary-result-is-err.mts:21