instead-of-math.h File Reference

instead-of-math.h - header to be included instead of math.h More...

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Functions
static void	sincos (double angle_rad, double *sinA, double *cosA)
	Calculates sine and cosine of an angle. More...
static double	normalize (double x, double range)
	Normalizes a cyclic double precision floating point variable x to the interval [0, range), assuming range is > 0. More...

Detailed Description

instead-of-math.h - header to be included instead of math.h

Author

David Hoadley vcrum.nosp@m.ble@.nosp@m.westn.nosp@m.et.c.nosp@m.om.au

This header needs to be included instead of the standard C library header math.h, in order to provide some routines that are missing or possibly missing from math.h. This header will include math.h for you.

The reason it must be included instead of math.h is a little obscure. One of the routines we want is the sincos() routine. Two versions of math.h actually do have it: The GNU C library does, and the Apple Clang library also has it, but under a different name.

The problem is, to gain access to the function, we need to include the appropriate incantation BEFORE including math.h if we are using the GNU C library, but we need to add definitions AFTER including math.h if we are using the Apple Clang library.

So use this header instead of math.h to look after this problem.

This header also provides the following missing function:

• normalize()
  A proper modulo function. Unlike fmod(), result is always positive. Used to to normalize a cyclic variable to a range, e.g. an angle in radian to the range [0, 2Pi), or an angle in degrees to the range [0, 360.0)

Copyright

Copyright (c) 2020, David Hoadley vcrum.nosp@m.ble@.nosp@m.westn.nosp@m.et.c.nosp@m.om.au All rights reserved.

Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

• Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.
• Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

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Definition in file instead-of-math.h.

Function Documentation

sincos()

static void sincos ( double  angle_rad, double *  sinA, double *  cosA  )

inlinestatic

Calculates sine and cosine of an angle.

Where the math library supports it, this is more efficient than calling sin() and cos() separately.

Parameters

[in]	angle_rad	Angle whose sine and cosine is wanted (radian)
[out]	sinA	sine of angle angle_rad
[out]	cosA	cosine of angle angle_rad

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Definition at line 114 of file instead-of-math.h.

normalize()

static double normalize ( double  x, double  range  )

inlinestatic

Normalizes a cyclic double precision floating point variable x to the interval [0, range), assuming range is > 0.

(If range is negative, this will normalize x to the interval (range, 0], but this is not the main use case for this function.)

Returns

The value of x, within the range [0, range)

Parameters

[in]	x	The variable (e.g. an angle in degrees or radian)
[in]	range	The range to normalize x to (e.g. 2Pi or 360.0). It must be non-zero.

This function returns the same results as fmod() for positive x and range. Where it differs is in its handling of negative values of x.

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Definition at line 144 of file instead-of-math.h.