# Triangular Parts
> BLAS matrix triangles.
## Usage
```javascript
var matrixTriangles = require( '@stdlib/blas/base/matrix-triangles' );
```
#### matrixTriangles()
Returns a list of BLAS matrix triangles.
```javascript
var out = matrixTriangles();
// e.g., returns [ 'upper', 'lower' ]
```
The output array contains the following types:
- `upper`: upper triangular part of a matrix.
- `lower`: lower triangular part of a matrix.
## Examples
```javascript
var contains = require( '@stdlib/array/base/assert/contains' ).factory;
var matrixTriangles = require( '@stdlib/blas/base/matrix-triangles' );
var isMatrixTriangle = contains( matrixTriangles() );
var bool = isMatrixTriangle( 'lower' );
// returns true
bool = isMatrixTriangle( 'upper' );
// returns true
bool = isMatrixTriangle( 'beep' );
// returns false
```
* * *
## C APIs
### Usage
```c
#include "stdlib/blas/base/matrix_triangles.h"
```
#### STDLIB_BLAS_MATRIX_TRIANGLE
An enumeration of BLAS matrix triangles with the following fields:
- **STDLIB_BLAS_UPPER**: upper triangular part of a matrix.
- **STDLIB_BLAS_LOWER**: lower triangular part of a matrix.
```c
#include "stdlib/blas/base/matrix_triangles.h"
const enum STDLIB_BLAS_MATRIX_TRIANGLE v = STDLIB_BLAS_LOWER;
```
### Notes
- Enumeration constants should be considered opaque values, and one should **not** rely on specific integer values.