| /* s_cosl.c -- long double version of s_sin.c. |
| * Conversion to long double by Jakub Jelinek, jj@ultra.linux.cz. |
| */ |
| |
| /* |
| * ==================================================== |
| * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. |
| * |
| * Developed at SunPro, a Sun Microsystems, Inc. business. |
| * Permission to use, copy, modify, and distribute this |
| * software is freely granted, provided that this notice |
| * is preserved. |
| * ==================================================== |
| */ |
| |
| #include <config.h> |
| |
| /* Specification. */ |
| #include <math.h> |
| |
| #if HAVE_SAME_LONG_DOUBLE_AS_DOUBLE |
| |
| long double |
| cosl (long double x) |
| { |
| return cos (x); |
| } |
| |
| #else |
| |
| /* Code based on glibc/sysdeps/ieee754/ldbl-128/s_cosl.c. */ |
| |
| /* cosl(x) |
| * Return cosine function of x. |
| * |
| * kernel function: |
| * __kernel_sinl ... sine function on [-pi/4,pi/4] |
| * __kernel_cosl ... cosine function on [-pi/4,pi/4] |
| * __ieee754_rem_pio2l ... argument reduction routine |
| * |
| * Method. |
| * Let S,C and T denote the sin, cos and tan respectively on |
| * [-PI/4, +PI/4]. Reduce the argument x to y1+y2 = x-k*pi/2 |
| * in [-pi/4 , +pi/4], and let n = k mod 4. |
| * We have |
| * |
| * n sin(x) cos(x) tan(x) |
| * ---------------------------------------------------------- |
| * 0 S C T |
| * 1 C -S -1/T |
| * 2 -S -C T |
| * 3 -C S -1/T |
| * ---------------------------------------------------------- |
| * |
| * Special cases: |
| * Let trig be any of sin, cos, or tan. |
| * trig(+-INF) is NaN, with signals; |
| * trig(NaN) is that NaN; |
| * |
| * Accuracy: |
| * TRIG(x) returns trig(x) nearly rounded |
| */ |
| |
| # include "trigl.h" |
| |
| long double |
| cosl (long double x) |
| { |
| long double y[2],z=0.0L; |
| int n; |
| |
| /* cosl(NaN) is NaN */ |
| if (isnanl (x)) |
| return x; |
| |
| /* |x| ~< pi/4 */ |
| if (x >= -0.7853981633974483096156608458198757210492 |
| && x <= 0.7853981633974483096156608458198757210492) |
| return kernel_cosl(x, z); |
| |
| /* cosl(Inf) is NaN, cosl(0) is 1 */ |
| else if (x + x == x && x != 0.0) |
| return x - x; /* NaN */ |
| |
| /* argument reduction needed */ |
| else |
| { |
| n = ieee754_rem_pio2l (x, y); |
| switch (n & 3) |
| { |
| case 0: |
| return kernel_cosl (y[0], y[1]); |
| case 1: |
| return -kernel_sinl (y[0], y[1], 1); |
| case 2: |
| return -kernel_cosl (y[0], y[1]); |
| default: |
| return kernel_sinl (y[0], y[1], 1); |
| } |
| } |
| } |
| |
| #endif |
| |
| #if 0 |
| int |
| main (void) |
| { |
| printf ("%.16Lg\n", cosl (0.7853981633974483096156608458198757210492)); |
| printf ("%.16Lg\n", cosl (0.7853981633974483096156608458198757210492 *29)); |
| printf ("%.16Lg\n", cosl (0.7853981633974483096156608458198757210492 *2)); |
| printf ("%.16Lg\n", cosl (0.7853981633974483096156608458198757210492 *30)); |
| printf ("%.16Lg\n", cosl (0.7853981633974483096156608458198757210492 *4)); |
| printf ("%.16Lg\n", cosl (0.7853981633974483096156608458198757210492 *32)); |
| printf ("%.16Lg\n", cosl (0.7853981633974483096156608458198757210492 *2/3)); |
| printf ("%.16Lg\n", cosl (0.7853981633974483096156608458198757210492 *4/3)); |
| } |
| #endif |