fix typo in crosses, more flexible generation
fix typo in crosses, more flexible generation

d-mittal/pystruct,amueller/pystruct,amueller/pystruct,pystruct/pystruct,massmutual/pystruct,d-mittal/pystruct,wattlebird/pystruct,massmutual/pystruct,wattlebird/pystruct,pystruct/pystruct