1 #include <u.h>
2 #include <libc.h>
3 #include "map.h"
4
5 static int
Xlagrange(struct place * place,double * x,double * y)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
lagrange(void)27 lagrange(void)
28 {
29 return(Xlagrange);
30 }
31