// Cross Polytope in n dimensions.
#include <stdlib.h>
#include "l.h"
static int gcount(int x) {int c=0; while(x){++c; x &= x-1;} return c;}

bp gcp(int n){
  R * wh = (R*)malloc((2*n)*n*sizeof(R));
  short * tp = (short *)malloc((1<<n)*n*sizeof(short));
  {int j=(2*n)*n; while(j--) wh[j]= 0;}
  {int j=n*n; while(j--) {wh[2*j*n + j] = 1; wh[(2*j+1)*n + j] = -1;}}
  {int j=1<<n; while(j--) {{int k = n; while(k--) tp[j*n + k] = 2*k + !!(j & (1<<k));}
     if(gcount(j) & 1) {short t = tp[j*n]; tp[j*n] = tp[j*n + 1]; tp[j*n + 1] = t;}}}
  return (bp){n, 2*n, wh, 1<<n, tp};}

#if 0
#include <stdio.h>
int main(){bp x = gcp(5);
  pm((mat){x.wh, x.vc, x.d}, "xes");
  {int j=x.sc; while(j--) {int k=x.d; printf("["/*]*/);
      while(k--) printf("%3d; ", x.c[j*x.d + k]); printf(/*[*/"];\n");}}
  return 0;}
// the yield of this test code is for the boundary tester at:
// http://cap-lore.com/MathPhys/IP/ocaml/bndry.html
#endif