defined Expr
prooved some theorems
add Hypothesis
Merge branch 'change_expr_def' into develop
implemented string to church
Merge branch 'feature_string_to_church' into develop
implemented church to string
Merge branch 'feature_church_stream_to_string' into develop
implemented Expr as lambda calculus
Merge branch 'feature_Expr_new_def' into develop
use ocamllex and ocamlyacc
changed .gitignore
use command line arguments
implemented
Merge branch 'develop'