Machine Problem 7, designed by Bryan Chadwick

In directory x is a class dictionary for a simple PL
with numbers and booleans with single argument lambdas.

The Evaluator handles LetRec and Mutiple Arg Lambdas without any 
changes to the code (just an adjustment of the 
field name "formal" -> "formals" in the Edge 
control) so you will not need to change EvalFunc.java or LetrecEvalFunc.java.

You should proceed as follows:

1) Read through and understand the Code (at least the important parts).  
You will be changing
the files in the 'extra' directory, 
but you shouldn't need to make any changes to more than
3 lines of already written code. I setup the files so that
the files Letrec*.java contain all the code dealing with the new constructs.

2) Get the Jar working... For this mp there is
a new version of the Jar. Bryan added an
initialization check that Edges to be bypassed actually exist; 
this will help you
to debug in the single to multiple args conversion.  
The method lookup is also much better
with some decent output available for debugging.

Util.setDebug(true) and/or Bc.setDebug(true) should help if they get stuck
Karl: what is Bc?

3) Add code for LetrecAddrTrans.java which helps 
transform Syms into Addr for the Evaluator
- To help you in this step Bryan added a command 
line 'switch' to Main to disable the type checking or evaluation.  
Running DemeterJ as:

demeterj test NoTypeCheck     or
demeterj test NoRun

will skip type-checking or evaluation respectively, 
so you can test parts of your implementation separately.

4) Add Code for LetrecTypeChecker.java to type-check LetRecs.  
Here you need to update the type environment, 
(TEnv update(LetRec l, TEnv te){ ... }) and do checking of LetRec
(Type combine(LetRec l, Type a, Type e, Type body){ ... })

5) Update program.beh, TypeChecker.java, and AddrTrans.java 
to support multiple arg Lambdas.


It seems like some work, but it's really only 20 lines of code, 
and almost no code modification. 
I included some simple but interesting tests for 
stages of letrec, and multiple arguments [of course factorial is there :)].

The new jar is placed at:
    /home/chadwick/www/demeterf/mp7package.jar