pawn ( slight change needed for black pawns as well.)

pawn(x)=select(r->(r[1]-x[1]==1 && abs(r[2]-x[2])<2) && [r[1],r[2]]!=[x[1],x[2]],setbinop((x,y)->concat(x,y),[1,2,3,4,5,6,7,8],[1,2,3,4,5,6,7,8]))