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-rw-r--r--libm/float/ynf.c120
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diff --git a/libm/float/ynf.c b/libm/float/ynf.c
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--- a/libm/float/ynf.c
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-/* ynf.c
- *
- * Bessel function of second kind of integer order
- *
- *
- *
- * SYNOPSIS:
- *
- * float x, y, ynf();
- * int n;
- *
- * y = ynf( 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
- * IEEE 0, 30 10000 2.3e-6 3.4e-7
- *
- *
- * ERROR MESSAGES:
- *
- * message condition value returned
- * yn singularity x = 0 MAXNUMF
- * yn overflow MAXNUMF
- *
- * Spot checked against tables for x, n between 0 and 100.
- *
- */
-
-/*
-Cephes Math Library Release 2.2: June, 1992
-Copyright 1984, 1987, 1992 by Stephen L. Moshier
-Direct inquiries to 30 Frost Street, Cambridge, MA 02140
-*/
-
-#include <math.h>
-extern float MAXNUMF, MAXLOGF;
-
-float y0f(float), y1f(float), logf(float);
-
-float ynf( int nn, float xx )
-{
-float x, an, anm1, anm2, r, xinv;
-int k, n, sign;
-
-x = xx;
-n = nn;
-if( n < 0 )
- {
- n = -n;
- if( (n & 1) == 0 ) /* -1**n */
- sign = 1;
- else
- sign = -1;
- }
-else
- sign = 1;
-
-
-if( n == 0 )
- return( sign * y0f(x) );
-if( n == 1 )
- return( sign * y1f(x) );
-
-/* test for overflow */
-if( x <= 0.0 )
- {
- mtherr( "ynf", SING );
- return( -MAXNUMF );
- }
-if( (x < 1.0) || (n > 29) )
- {
- an = (float )n;
- r = an * logf( an/x );
- if( r > MAXLOGF )
- {
- mtherr( "ynf", OVERFLOW );
- return( -MAXNUMF );
- }
- }
-
-/* forward recurrence on n */
-
-anm2 = y0f(x);
-anm1 = y1f(x);
-k = 1;
-r = 2 * k;
-xinv = 1.0/x;
-do
- {
- an = r * anm1 * xinv - anm2;
- anm2 = anm1;
- anm1 = an;
- r += 2.0;
- ++k;
- }
-while( k < n );
-
-
-return( sign * an );
-}