98 lines
1.6 KiB
C
98 lines
1.6 KiB
C
/* polevl.c
|
||
* p1evl.c
|
||
*
|
||
* Evaluate polynomial
|
||
*
|
||
*
|
||
*
|
||
* SYNOPSIS:
|
||
*
|
||
* int N;
|
||
* double x, y, coef[N+1], polevl[];
|
||
*
|
||
* y = polevl( x, coef, N );
|
||
*
|
||
*
|
||
*
|
||
* DESCRIPTION:
|
||
*
|
||
* Evaluates polynomial of degree N:
|
||
*
|
||
* 2 N
|
||
* y = C + C x + C x +...+ C x
|
||
* 0 1 2 N
|
||
*
|
||
* Coefficients are stored in reverse order:
|
||
*
|
||
* coef[0] = C , ..., coef[N] = C .
|
||
* N 0
|
||
*
|
||
* The function p1evl() assumes that coef[N] = 1.0 and is
|
||
* omitted from the array. Its calling arguments are
|
||
* otherwise the same as polevl().
|
||
*
|
||
*
|
||
* SPEED:
|
||
*
|
||
* In the interest of speed, there are no checks for out
|
||
* of bounds arithmetic. This routine is used by most of
|
||
* the functions in the library. Depending on available
|
||
* equipment features, the user may wish to rewrite the
|
||
* program in microcode or assembly language.
|
||
*
|
||
*/
|
||
|
||
|
||
/*
|
||
Cephes Math Library Release 2.1: December, 1988
|
||
Copyright 1984, 1987, 1988 by Stephen L. Moshier
|
||
Direct inquiries to 30 Frost Street, Cambridge, MA 02140
|
||
*/
|
||
|
||
|
||
double polevl( x, coef, N )
|
||
double x;
|
||
double coef[];
|
||
int N;
|
||
{
|
||
double ans;
|
||
int i;
|
||
double *p;
|
||
|
||
p = coef;
|
||
ans = *p++;
|
||
i = N;
|
||
|
||
do
|
||
ans = ans * x + *p++;
|
||
while( --i );
|
||
|
||
return( ans );
|
||
}
|
||
|
||
/* p1evl() */
|
||
/* N
|
||
* Evaluate polynomial when coefficient of x is 1.0.
|
||
* Otherwise same as polevl.
|
||
*/
|
||
|
||
double p1evl( x, coef, N )
|
||
double x;
|
||
double coef[];
|
||
int N;
|
||
{
|
||
double ans;
|
||
double *p;
|
||
int i;
|
||
|
||
p = coef;
|
||
ans = x + *p++;
|
||
i = N-1;
|
||
|
||
do
|
||
ans = ans * x + *p++;
|
||
while( --i );
|
||
|
||
return( ans );
|
||
}
|