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