> ## Documentation Index
> Fetch the complete documentation index at: https://docs.classiq.io/llms.txt
> Use this file to discover all available pages before exploring further.

# Unary Iteration

Functions:

| Name | Description |
| - | - |
| `unary_select` | \[Qmod Classiq-library function]. |

### unary\_select

<pre><code>unary\_select(
unitaries: QCallableList,
selector: Const\[QNum]
) -> None</code></pre>

\[Qmod Classiq-library function]

Implements an unconditional SELECT oracle using unary iteration
(Babbush et al., arXiv:1805.03662, Section III.A).

The operation maps:

$|\ell\rangle|\psi\rangle \to |\ell\rangle\, U_\ell\,|\psi\rangle$

Uses the MSB of the selector as the root branch indicator, requiring
one fewer auxiliary qubit than a controlled variant would.

**Parameters:**

| Name | Type | Description | Default |
| - | - | - | - |
| `unitaries` | `QCallableList` | Quantum callables $U_0, \ldots, U_\{L-1\}$. | *required* |
| `selector` | `Const[QNum]` | Quantum register encoding the index $\ell$ in binary. | *required* |