vatexspi - Vector half-cycle exsecant exs(πx)

15.1 vatexspi - Vector half-cycle exsecant $exs(πx)$

subroutine vatexspi (n, y, incy, x, incx); 
subroutine vatexspif(n, y, incy, x, incx); 
 
subroutine vatexspi_64 (n, y, incy, x, incx); 
subroutine vatexspif_64(n, y, incy, x, incx);

Given an input vector $x$ and a result vector $y$ , this function computes:

y= exs(πx)= --1----1 cos(πx)

15.1.1 Parameters

N - INTEGER: ENTRY: Number of elements of $x$ and $y$ .
CONSTRAINT: $n ≥1$ .
Y - ARRAY OF REAL: EXIT: Result vector $y$ .
CONSTRAINT: Must contain $n× incy$ elements.
CONSTRAINT: Must not overlap with array $x$ .
INCY - INTEGER: ENTRY: Stride for the vector $y$ .
CONSTRAINT: $incy̸= 0$ .
BEHAVIOR: A negative stride will traverse the array in reverse.
X - ARRAY OF REAL: ENTRY: Input vector $x$ .
CONSTRAINT: Must contain $n× incx$ elements.
CONSTRAINT: Must not overlap with array $y$ .
INCX - INTEGER: ENTRY: Stride for the vector $x$ .
CONSTRAINT: $incx̸= 0$ .
BEHAVIOR: A negative stride will traverse the array in reverse.

15.1.2 Function Graphs

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