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Diffstat (limited to 'libm/double/yn.c')
-rw-r--r-- | libm/double/yn.c | 114 |
1 files changed, 0 insertions, 114 deletions
diff --git a/libm/double/yn.c b/libm/double/yn.c deleted file mode 100644 index 0c569a925..000000000 --- a/libm/double/yn.c +++ /dev/null @@ -1,114 +0,0 @@ -/* yn.c - * - * Bessel function of second kind of integer order - * - * - * - * SYNOPSIS: - * - * double x, y, yn(); - * int n; - * - * y = yn( n, x ); - * - * - * - * DESCRIPTION: - * - * Returns Bessel function of order n, where n is a - * (possibly negative) integer. - * - * The function is evaluated by forward recurrence on - * n, starting with values computed by the routines - * y0() and y1(). - * - * If n = 0 or 1 the routine for y0 or y1 is called - * directly. - * - * - * - * ACCURACY: - * - * - * Absolute error, except relative - * when y > 1: - * arithmetic domain # trials peak rms - * DEC 0, 30 2200 2.9e-16 5.3e-17 - * IEEE 0, 30 30000 3.4e-15 4.3e-16 - * - * - * ERROR MESSAGES: - * - * message condition value returned - * yn singularity x = 0 MAXNUM - * yn overflow MAXNUM - * - * Spot checked against tables for x, n between 0 and 100. - * - */ - -/* -Cephes Math Library Release 2.8: June, 2000 -Copyright 1984, 1987, 2000 by Stephen L. Moshier -*/ - -#include <math.h> -#ifdef ANSIPROT -extern double y0 ( double ); -extern double y1 ( double ); -extern double log ( double ); -#else -double y0(), y1(), log(); -#endif -extern double MAXNUM, MAXLOG; - -double yn( n, x ) -int n; -double x; -{ -double an, anm1, anm2, r; -int k, sign; - -if( n < 0 ) - { - n = -n; - if( (n & 1) == 0 ) /* -1**n */ - sign = 1; - else - sign = -1; - } -else - sign = 1; - - -if( n == 0 ) - return( sign * y0(x) ); -if( n == 1 ) - return( sign * y1(x) ); - -/* test for overflow */ -if( x <= 0.0 ) - { - mtherr( "yn", SING ); - return( -MAXNUM ); - } - -/* forward recurrence on n */ - -anm2 = y0(x); -anm1 = y1(x); -k = 1; -r = 2 * k; -do - { - an = r * anm1 / x - anm2; - anm2 = anm1; - anm1 = an; - r += 2.0; - ++k; - } -while( k < n ); - - -return( sign * an ); -} |