1: $n$ – Integer Input: On entry: $n$ , the number of elements in $x$ and $y$ .
2: $alpha$ – Real (Kind=nag_wp) Input: On entry: the scalar $α$ .
3: $x (*)$ – Real (Kind=nag_wp) array Input: Note: the dimension of the array x must be at least $\max (1, 1 + (n - 1) \times | incx |)$ .

On entry: the $n$ -element vector $x$ .
If $incx > 0$ , $x_{i}$ must be stored in $x (1 + (i - 1) \times incx)$ , for $i = 1, 2, \dots, n$ .

If $incx < 0$ , $x_{i}$ must be stored in $x (1 - (n - i) \times incx)$ , for $i = 1, 2, \dots, n$ .

Intermediate elements of x are not referenced.
4: $incx$ – Integer Input: On entry: the increment in the subscripts of x between successive elements of $x$ .
5: $y (*)$ – Real (Kind=nag_wp) array Input/Output: Note: the dimension of the array y must be at least $\max (1, 1 + (n - 1) \times | incy |)$ .

On entry: if $| incy | \neq 1$ , intermediate elements of y may contain values and will not be referenced; the other elements will be overwritten and need not be set.

On exit: the elements $y_{i}$ of the vector $y$ will be stored in y as follows.
If $incy > 0$ , $y_{i}$ will be stored in $y (1 + (i - 1) \times incy)$ , for $i = 1, 2, \dots, n$ .

If $incy < 0$ , $y_{i}$ will be stored in $y (1 - (n - i) \times incy)$ , for $i = 1, 2, \dots, n$ .

Intermediate elements of y are unchanged.
6: $incy$ – Integer Input: On entry: the increment in the subscripts of y between successive elements of $y$ .