型！　型！ ref: http://qiita.com/minamiyama1994/items/f640e6fd02197709b35b

file0.txt

def to_string(value)
  value.to_s
end

file1.hs

toString :: Show a => a -> String
toString value = show value

file2.cpp

template < typename T >
auto to_string ( const T & value ) -> std::string
{
    return boost::lexical_cast < std::string > ( value ) ;
}

file3.hs

hoge :: [ a ] -> Int
hoge l = length l

file4.hs

hoge :: a -> b

file5.txt

Goal forall A B C : Prop , ( A -> B ) -> ( B -> C ) -> ( A -> C ).
Proof.
  intros.
  apply H0.
  apply H.
  apply H1.
Qed.