a = where(ltest, LatticeFermion(sitefield), zero);
LatticeFermion tmp; tmp = sitefield;  a = where(ltest, tmp, LatticeFermion(zero));
void walfil(LatticeFermion& a, int slice, int mu, int color_index){  START_CODE("walfil");  if ( color_index >= Nc )    QDP_error_exit("Color index out of bounds", color_index, Nc);  if ( (slice % 2) != 0 )    QDP_error_exit("Require an even valued slice", slice);  /*    * Write ONE to the even coordinates of the appropriate slice.    * Note: staggered fermions are represented as "Ns=1" spinors!    */  // Write ONE to all field  int spin_index = 0;  Real one = 1;  Complex sitecomp = cmplx(one,0);  ColorVector sitecolor = zero;  Fermion sitefield = zero;  pokeSpin(sitefield,	   pokeColor(sitecolor,sitecomp,color_index),	   spin_index);  // Narrow the context to the desired slice and to even coordinates  LatticeBoolean ltest = (Layout::latticeCoordinate(mu) == slice);  for(int m = 0; m < Nd; ++m)    if ( m != mu )      ltest &= (mod(Layout::latticeCoordinate(m), 2) == 0);  // Write onto the appropriate slice  a = where(ltest, LatticeFermion(sitefield), zero);  END_CODE("walfil");}