fun fu_alloc(ftype)
{
    assert(ftype?cvt(ulong) < 7 );
    if(ftype?cvt(ulong) >= 4 ) return true;
    if(fu_num_allocated[ftype] >= fu_pool[ftype])
	return false;
    fu_num_allocated[ftype] = fu_num_allocated[ftype] + 1;
    return true;
}