Whats what in the cfn.
 
 Language generated by cfn contains these ast node types:
   lambda
   let
   if
   case   -- restriction: all patterns must be either literals or
                          a constructor with var and wildcard args
   app
   var-ref
   con-ref
   const
   con-number
   sel
   is-constructor
 
 Transformations to do:
   Convert lists to explicit calls to cons
   Simplify patterns
   Remove sequences
   Remove list comprehensions
   Remove sections
   Reduce patterns on lhs of decls
   Reduce patterns in function args
   Convert where decls to let statements
   Convert guarded-expressions to if - then - else form
 
 Done earlier:
   signdecls are removed in scoping
   exp-signs are removed in typechecker
   prec parser removes `negate' & pp-* nodes