use better interface
use better interface


Former-commit-id: 1faec9bde3ed196387056cdb6e8a123a81955253
danielhers/dynet,shuheik/dynet,clab/dynet,clab/cnn,clab/dynet,shuheik/dynet,danielhers/dynet,chunyang-wen/dynet,xunzhang/dynet,clab/dynet,chunyang-wen/dynet,chunyang-wen/dynet,shuheik/dynet,clab/cnn,danielhers/dynet,shuheik/dynet,xunzhang/dynet,danielhers/dynet,xunzhang/dynet,shuheik/dynet,shuheik/dynet,xunzhang/dynet,danielhers/dynet,clab/dynet,danielhers/dynet,danielhers/dynet,clab/cnn,clab/dynet,shuheik/dynet,chunyang-wen/dynet,clab/dynet,clab/dynet