* Update program.md
* Update
* Update

* fix block syntax

* add builder

* fix argument names

* uniform all Var to var

* fix c demo

* factor set_outputs

* update block

* delete as_ifelse_input interface from block design

* simplify set_outputs and output_num

* make the c++ codes compatible with demo

* fix compatible

* fix syntax

* update ie

* update syntax

Fixes #4445

* some enforce change

* add LoDTensor::NumElements(id,id)

* update

* init

* finish

* refacter interfaces