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#ifndef lint
static const char SCCSID[]="@(#)nad_cvt.c 4.3 95/09/23 GIE REL";
#endif
#define PJ_LIB__
#include <projects.h>
#define MAX_TRY 9
#define TOL 1e-12
LP
nad_cvt(LP in, int inverse, struct CTABLE *ct) {
LP t, tb;
if (in.lam == HUGE_VAL)
return in;
/* normalize input to ll origin */
tb = in;
tb.lam -= ct->ll.lam;
tb.phi -= ct->ll.phi;
tb.lam = adjlon(tb.lam);
t = nad_intr(tb, ct);
if (inverse) {
LP del, dif;
int i = MAX_TRY;
if (t.lam == HUGE_VAL) return t;
t.lam = tb.lam + t.lam;
t.phi = tb.phi - t.phi;
do {
del = nad_intr(t, ct);
if (del.lam == HUGE_VAL) return del;
t.lam -= dif.lam = t.lam - del.lam - tb.lam;
t.phi -= dif.phi = t.phi + del.phi - tb.phi;
} while (i-- && fabs(dif.lam) > TOL && fabs(dif.phi) > TOL);
if (i < 0) {
t.lam = t.phi = HUGE_VAL;
return t;
}
in.lam = adjlon(t.lam + ct->ll.lam);
in.phi = t.phi + ct->ll.phi;
} else {
if (t.lam == HUGE_VAL)
in = t;
else {
in.lam -= t.lam;
in.phi += t.phi;
}
}
return in;
}
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