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/******************************************************************************
* Project: PROJ
* Purpose: Make C99 math functions available on C89 systems
* Author: Kristian Evers
*
******************************************************************************
* Copyright (c) 2018, Kristian Evers
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, including without limitation
* the rights to use, copy, modify, merge, publish, distribute, sublicense,
* and/or sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included
* in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
* OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
* DEALINGS IN THE SOFTWARE.
*****************************************************************************/
#include "proj_math.h"
#if !(defined(HAVE_C99_MATH) && HAVE_C99_MATH)
/* Compute hypotenuse */
double pj_hypot(double x, double y) {
x = fabs(x);
y = fabs(y);
if ( x < y ) {
x /= y;
return ( y * sqrt( 1. + x * x ) );
} else {
y /= (x != 0.0 ? x : 1.0);
return ( x * sqrt( 1. + y * y ) );
}
}
/* Compute log(1+x) accurately */
double pj_log1p(double x) {
volatile double
y = 1 + x,
z = y - 1;
/* Here's the explanation for this magic: y = 1 + z, exactly, and z
* approx x, thus log(y)/z (which is nearly constant near z = 0) returns
* a good approximation to the true log(1 + x)/x. The multiplication x *
* (log(y)/z) introduces little additional error. */
return z == 0 ? x : x * log(y) / z;
}
/* Compute asinh(x) accurately */
double pj_asinh(double x) {
double y = fabs(x); /* Enforce odd parity */
y = log1p(y * (1 + y/(hypot(1.0, y) + 1)));
return x > 0 ? y : (x < 0 ? -y : x);
}
/* Returns 0 if not a NaN and non-zero if val is a NaN */
int pj_isnan (double x) {
/* cppcheck-suppress duplicateExpression */
return x != x;
}
#endif /* !(defined(HAVE_C99_MATH) && HAVE_C99_MATH) */
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