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/* reduce argument to range +/- PI */
#ifndef lint
static const char SCCSID[]="@(#)adjlon.c 4.3 93/06/12 GIE REL";
#endif
#include <math.h>
#define SPI 3.14159265359
#define TWOPI 6.2831853071795864769
#define ONEPI 3.14159265358979323846
double adjlon (double lon) {
if (fabs(lon) <= SPI) return( lon );
lon += ONEPI; /* adjust to 0..2pi rad */
lon -= TWOPI * floor(lon / TWOPI); /* remove integral # of 'revolutions'*/
lon -= ONEPI; /* adjust back to -pi..pi rad */
return( lon );
}
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