# Given a list mis of subsets of X of the same cardinality, determine
# if there is a partition of X into blocks, each of which appear in mis.
# If so, assign the partition to args[3].

tight:=proc(mis,X) local i,j,l,new,c,m;
  if X=mis[1] then assign(args[3],[X]); RETURN(true) fi;
  m:=nops(mis[1]);
  for i to nops(mis) do
    if nops(X)=k0*m then lprint(i,time()) fi;
    new:=subs({seq(j=NULL,j=mis[i])},[op(i+1..nops(mis),mis)]);
    new:=map(proc(x,y) if nops(x)=y then x fi end,new,m);
    if nops({op(map(op,new))})+m=nops(X)
      and procname(new,X minus mis[i],'c') then
      assign(args[3],[mis[i],op(c)]); RETURN(true) fi;
  od; false
end: