# Diagonal Element Types
> BLAS diagonal element types.
## Usage
```javascript
var diagonalTypes = require( '@stdlib/blas/base/diagonal-types' );
```
#### diagonalTypes()
Returns a list of BLAS diagonal element types.
```javascript
var out = diagonalTypes();
// e.g., returns [ 'non-unit', 'unit' ]
```
The output array contains the following types:
- `non-unit`: elements along a diagonal are **not** all equal to one.
- `unit`: elements along a diagonal are all equal to one.
## Examples
```javascript
var contains = require( '@stdlib/array/base/assert/contains' ).factory;
var diagonalTypes = require( '@stdlib/blas/base/diagonal-types' );
var isDiagonalType = contains( diagonalTypes() );
var bool = isDiagonalType( 'non-unit' );
// returns true
bool = isDiagonalType( 'unit' );
// returns true
bool = isDiagonalType( 'beep' );
// returns false
```
* * *
## C APIs
### Usage
```c
#include "stdlib/blas/base/diagonal_types.h"
```
#### STDLIB_BLAS_DIAGONAL_TYPE
An enumeration of BLAS diagonal element types with the following fields:
- **STDLIB_BLAS_NON_UNIT_DIAGONAL**: elements along a diagonal are **not** all equal to one.
- **STDLIB_BLAS_UNIT_DIAGONAL**: elements along a diagonal are all equal to one.
```c
#include "stdlib/blas/base/diagonal_types.h"
const enum STDLIB_BLAS_DIAGONAL_TYPE v = STDLIB_BLAS_UNIT_DIAGONAL;
```
### Notes
- Enumeration constants should be considered opaque values, and one should **not** rely on specific integer values.