# AllowAtMostNQubits operation

Namespace: Microsoft.Quantum.Diagnostics

Package: Microsoft.Quantum.Standard

Between a call to this operation and its adjoint, asserts that at most a given number of additional qubits are allocated with using statements.

operation AllowAtMostNQubits (nQubits : Int, message : String) : Unit is Adj


## Input

### nQubits : Int

The maximum number of qubits that may be allocated.

### message : String

A message to be displayed upon failure.

## Example

The following snippet will fail when executed on machines which support this diagnostic:

within {
AllowAtMostNQubits(3, "Too many qubits allocated.");
} apply {
// Fails since this allocates four qubits.
using (register = Qubit[4]) {
}
}


## Remarks

This operation may be replaced by a no-op on targets which do not support it.