Reduced row echelon form of a matrix.

mat | The input matrix. |

return value | The reduced row echelon form of the matrix. |

Reduced row echelon form is an upper triangular form similar to one returned by gauss. The main difference is that in reduced row ecehelon form the leading coefficient of all rows is normalized to 1, and all the numbers in its column must be 0, except the given row itself.

```
rref(
```*[1,2;3,2]*)

```
a=
```*[1,2;3,2]*;
gauss(a)
rref(a)