---
title: "initializer_list"
---

{{< callout type="info">}}
  Header: `initializer_list.h`  
  From: `20.24.0`  
  Similar to: [initializer_list](https://en.cppreference.com/cpp/utility/initializer_list)
{{< /callout >}}

```cpp
template <typename T>
class initializer_list
```

## Special case
The `initializer_list` template class is a special case in that it *must* have a definition that is compatible with what the compiler expects. It *must* also be defined under the `std` namespace.  

This header will either include the standard `<initializer_list>` header, or attempt to define a `std::initializer_list` template class that is compatible with the current compiler.  

The header will define `ETL_USING_INITIALIZER_LIST` to either `1` or `0` dependant of whether `std::initializer_list` is available or not.  

The ETL will select the STL version if you are using the STL and `ETL_FORCE_ETL_INITIALIZER_LIST` is not defined or, 
`ETL_FORCE_STD_INITIALIZER_LIST` is defined.  

The ETL's version will be selected if you are not using the STL or `ETL_FORCE_ETL_INITIALIZER_LIST` is defined.  

## What issues might I come across?
If you are not using the STL, and one of the system headers or libraries that you include reference the standard initializer_list definition then the compiler will complain of duplicate definitions. In this case you will have to force the ETL to use the STL definition. There are two macros that force selection of one or other definition.  

Define one of these macros to force the selection.  
`ETL_FORCE_ETL_INITIALIZER_LIST`  
`ETL_FORCE_STD_INITIALIZER_LIST`  

Defining `ETL_NO_INITIALIZER_LIST` will disable the use of `std::initializer_list` for the ETL.

---

If you get "No definition for initializer_list is currently available for your compiler", visit [https://github.com/ETLCPP/etl/issues](https://github.com/ETLCPP/etl/issues) to request support, it may be that neither of the ETL definitions of `initializer_list` are compatible with your compiler. In that case please raise an issue here.  

Alternatively, your compiler may be compatible with GCC/clang. Try adding the compiler's Identifier macro to the conditional compilation directive.
