---
title: "threshold"
---

{{< callout type="info">}}
  Header: `threshold.h`  
  Since: `20.9.0`  
{{< /callout >}}

```cpp
template <typename TInput, typename TCompare = etl::less<TInput> >
class threshold : public etl::unary_function<TInput, TInput>
```

`TInput`   The input data type.  
`TCompare` The functor type used to compare values to the threshold. The default is `etl::less`.

---

```cpp
threshold(TInput   threshold_value, 
          TInput   true_value, 
          TInput   false_value, 
          TCompare compare = TCompare())
```
**Description**  
Constructor.

---

```cpp
TInput operator()(TInput value) const
```
Threshold a value.

## Example
```cpp
std::array<int, 10> input
{
  0, 1, 2, 3, 4, 5, 6, 7, 8, 9
};

std::array<int, 10> output;

etl::threshold<int> threshold(4, 0, 9); // Compares each value to 4 and output 0 or 9.

std::transform(input.begin(), input.end(), output.begin(), threshold);

// output == 0, 0, 0, 0, 9, 9, 9, 9, 9, 9
```