  We present an inference system for a version of the Pi-calculus in Haskell
for the session type proposed by Honda et al. The session type is very useful
in checking if the communications are well-behaved. The full session type
implementation in Haskell was first presented by Pucella and Tov, which is
'semi-automatic' in that the manual operations for the type representation was
necessary. We give an automatic type inference for the session type by using a
more abstract representation for the session type based on the 'de Bruijn
levels'. We show an example of the session type inference for a simple SMTP
client.
