mutually recursive types
Merge branch 'master' of https://github.com/archaeron/Calculon

* 'master' of https://github.com/archaeron/Calculon:
  mistakes have been made
  Revert "Revert "repl ported from @JorisM""
  Revert "repl ported from @JorisM"
  repl ported from @JorisM
  package for VS
  added a VS file to the gitignore