lfe

   Copyright (c) 2013 Robert Virding

   Licensed under the Apache License, Version 2.0 (the "License");
   you may not use this file except in compliance with the License.
   You may obtain a copy of the License at

       http://www.apache.org/licenses/LICENSE-2.0

   Unless required by applicable law or agreed to in writing, software
   distributed under the License is distributed on an "AS IS" BASIS,
   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   See the License for the specific language governing permissions and
   limitations under the License.


Implementation Notes
--------------------

Translating LFE <-> Erlang
--------------------------

The only complications are handling the variable scoping and
converting between them. Some example cases:

X = b(x),                   (progn
X = c(y),                     (let ((X (when) (b 'x)))
a(X, X).                        (let ((---0--- (when (=:= X ---0---)) (c 'y)))
                                  (a X X))))

Can only handle case of binding variable at "top level" in
expressions, nested expressions need to be flattened which introduces
a whole new level of complexity.

(let ((X (f 1)))                X = f(1),
  (a X)                         a(X),
  (let ((X (g X)))              ___0___ = g(X),
    (b X))                      b(___0___),
  (c X))                        c(X)

This is much easier as variables can never "escape" their scope, we
just have to generate unique variable names.