# #ifndef directive

Source: https://ref.dm-lang.org/DM/preprocessor/ifndef

### Format
> `#ifndef Name`

### Args
> Name: A macro definition.

The `#ifndef` statement is used to conditionally compile code. It is equivalent to `#if !defined(Name)`.

### See also
- [#define directive](https://ref.dm-lang.org/DM/preprocessor/define/index.md)
- [#if directive](https://ref.dm-lang.org/DM/preprocessor/if.md)
- [#ifdef directive](https://ref.dm-lang.org/DM/preprocessor/ifdef.md)
- [preprocessor](https://ref.dm-lang.org/DM/preprocessor/index.md)