use better interface
use better interface


Former-commit-id: 003ea7164cb150fbde23844049e2d3346231ee5a
clab/dynet,shuheik/dynet,clab/dynet,shuheik/dynet,xunzhang/dynet,danielhers/dynet,chunyang-wen/dynet,clab/dynet,clab/cnn,xunzhang/dynet,shuheik/dynet,clab/cnn,clab/dynet,clab/dynet,shuheik/dynet,chunyang-wen/dynet,shuheik/dynet,danielhers/dynet,chunyang-wen/dynet,danielhers/dynet,xunzhang/dynet,clab/cnn,xunzhang/dynet,danielhers/dynet,clab/dynet,shuheik/dynet,chunyang-wen/dynet,danielhers/dynet,clab/dynet,danielhers/dynet,shuheik/dynet,danielhers/dynet