tlagrange.c - plan9port - [fork] Plan 9 from user space
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       ---
       tlagrange.c (468B)
       ---
            1 #include <u.h>
            2 #include <libc.h>
            3 #include "map.h"
            4 
            5 static int
            6 Xlagrange(struct place *place, double *x, double *y)
            7 {
            8         double z1,z2;
            9         double w1,w2,t1,t2;
           10         struct place p;
           11         copyplace(place,&p);
           12         if(place->nlat.l<0) {
           13                 p.nlat.l = -p.nlat.l;
           14                 p.nlat.s = -p.nlat.s;
           15         }
           16         Xstereographic(&p,&z1,&z2);
           17         csqrt(-z2/2,z1/2,&w1,&w2);
           18         cdiv(w1-1,w2,w1+1,w2,&t1,&t2);
           19         *y = -t1;
           20         *x = t2;
           21         if(place->nlat.l<0)
           22                 *y = -*y;
           23         return(1);
           24 }
           25 
           26 proj
           27 lagrange(void)
           28 {
           29         return(Xlagrange);
           30 }