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# init(in:in_type:out:out_type:)

Returns a new arithmetic structure that takes a single input from the specified parameters.

```
init(in: BNNSNDArrayDescriptor, in_type: BNNSDescriptorType, out: BNNSNDArrayDescriptor, out_type: BNNSDescriptorType)
```

## Parameters

`in`

The descriptor of the input.

`in_type`

The descriptor type of the input.

`out`

The descriptor of the output.

`out_type`

The descriptor type of the output.

## Discussion

> Important:
> The input data type must be equal to the output data type. The input size must equal the output size or `1`. Arithmetic layers only support arrays with a data type of `float`, and a data layout of ``doc://com.apple.accelerate/documentation/Accelerate/BNNS/DataLayout/vector``, ``doc://com.apple.accelerate/documentation/Accelerate/BNNS/DataLayout/matrixRowMajor``, ``doc://com.apple.accelerate/documentation/Accelerate/BNNS/DataLayout/matrixColumnMajor``, or ``doc://com.apple.accelerate/documentation/Accelerate/BNNS/DataLayout/imageCHW``.

---

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