Assignment 5. Type Checker

Attached is the detailed specification of this assignment. It is also available in the /c/cs421/as/as5/README file on all the ZOO machines.

                   Assignment 5. Type Checker

Programming exercise described in Modern Compiler Implementation in ML, 
Chapter 5, on page 121 - 122. This assignment is to implement a type 
checker for the Tiger language. Please read Chapter 5 of Appel very 
CAREFULLY before starting to work on the assignment.  

You need to do both Part (a) and Part (b) of the type checker (see pp. 
121 - 122 of Appel). But it is a good idea to make Part (a) work correctly 
first before embarking on Part (b).

WARNING: sample code in Appel's book contains many syntactic errors, so 
don't try to copy the code from Appel's book into your semant.sml. 
Understand the problem and write your own code.

The "/c/cs421/as/as5" now contains the following files:

     absyn.sml
     errormsg.sml
     table.sig
     table.sml
     symbol.sml
     parse.sml
       These are copied from the "as4" directory.

     types.sml
       The internal representation of types.

     main.sml
       The top level program used to test your typechecker. 
       Function call "Main.comp fname" will parse and typecheck the
       tiger program in file "fname". Function call "Main.testit()" 
       will parse and typecheck all 49 tiger programs in the 
       "/c/cs421/as/testcases" directory.

     env.sml
     semant.sml
       The skeleton env.sml and semant.sml files. You need to fill in
       the details in these two files.

     sources.cm
       The makefile.

     sources-mine.cm
       The sources.cm file if you want to use my lexer and parser. 

To start working on the assignment, copy all the above files into
your working directory, copy your tiger.lex and tiger.grm file from your
previous assignments, then start writing "env.sml" and "semant.sml".

If your lexer or parser still does not work, you can use the 
"sources-mine.cm" file as your "sources.cm" file. This will use my lexer 
and parser instead. But I do NOT recommend this. I hope all of you will
spend time debugging through your old assignments and use your own lexer 
and parser in the future assignments.

Finally, you need to turn in the following three files 

     README (more documentation is better)
     env.sml
     semant.sml

This is probably the LARGEST assignment in this class. To most of you,
it would probably take days. Please start working on it as early as you 
can. Also please make sure that your type-checker prints out friendly
error messages. 

Enjoy,

-Zhong Shao
(shao-zhong@cs.yale.edu)