[A. Instructions]
  1. run 'make' to compile all necessary files
  2. run 'java Main < input_file > output.asm' for generating MIPS code
  3. run 'make tests' for testing all tests

[B. Assumptions]
  1. 'input_file' is a semantically valid MiniJava Variant source program
    MiniJava Variant: (VarDeclaration)* is added at the begining of 'main' in MainClass
    source: p-asgn4(1).docx
  2. MainClass will not have new instance or be a superclass of some class
    source: https://piazza.com/class/jb23yysuffr2fx?cid=130
  3. 'main' in MainClass will not be called except the initial one
    source: https://piazza.com/class/jb23yysuffr2fx?cid=130
  4. 'main'(except the only method in MainClass), 'length', 'String' cannot be used as identifier even though they are allowed in Java
    source: https://piazza.com/class/jb23yysuffr2fx?cid=130
  5. some keywords in Java are not considered as reserved if they have no specific meaning here (e.g. 'protected', 'interface', 'double')
    source: https://piazza.com/class/jb23yysuffr2fx?cid=130
  6. local variables will be initialized before using
    source: https://piazza.com/class/jb23yysuffr2fx?cid=132
  7. short-circuit is not required in And operator
    source: https://piazza.com/class/jb23yysuffr2fx?cid=113

[C. Tests]
  all cases can be handled, including 1-15 and 16(bonus)

[D. Acknowledgement]
  - some test are from piazza of CSCI3120 and  https://github.com/isaackwan/csci3120-minijava-testcases
  - no other use of third party code, files, and library

[E. Additional Information]
  - none

Update: May 3
  - Fix a bug in the ArrayLookup() production in minijava.jj.
  - Fix a bug in the PrimaryExpressionWithSuffix in minijava.jj.
  - Added a visitor method in CodeGenerator.java for ClassDeclSimple.
  - Added few more test cases for testing arrays, objects, and methods.

Update: May 2
  - Fix a major bug in the MIPS code (in CodeGenVisitor.java) for allocating
    array ("_alloc_int_array").

  - Fix a bug with the Not operator in minijava.jj to properly enforce
    operator precedence.

  - Rewrite PrimaryExpressionWithSuffix() in minijava.jj to improve performance.

  - Added many test cases in folder /test.

  - Included also the Mars4_5.jar in the folder /test.

  - Added a Makefile in /test to help testing the correctness of your
    code generator.


----------------------------------------------------------------------------------
Main.java:
  1) Use visitor/BuildSymbolTableVisitor to build a symbol table
  2) Use visitor/TypeCheckVisitor to perform type check
  3) Use visitor/CodeGenVisitor to generate MIPS code

MainPrettyPrint.java:
  Use visitor/PrettyPrintVisitor to reproduce the source
  (to help verify correctness of AST).

visitor/CodeGenVisitor.java:
  Added to support code generation (MiniJava to MIPS)
  Able to generate the initial "skeleton" of the program

  [Updated on 2 May]:
  - Fix a bug in the MIPS code for allocating array ("_alloc_int_array:") in
    which the size of the allocated space was assigned to $a1 instead of $a0.

  - Included also the visitor methods for This, IntegerLiteral, True, False, IdentifierExp.

  [Updated on 3 May]
  - Included the visitor method for ClassDeclSimple

test/:
  Contain some test cases

input/:
  Contain some valid MiniJava source files (for more comprehensive testing)


Files that are modified:
------------------------
minijava.jj:
  Modified to allow declaration of local variables in "public static void main()"

  [Updated on 2 May]:
   - Rewrote PrimaryExpressionWithSuffix() to improve performance (less lookhead).
     ArrayLookup(), ArrayLength(), and MessageSend() were modified to accomodate the
     change. The resulting AST is still the same.

   - Fix a bug in NotExpression() to properly enforce the precedence of the Not operator.
       Before: NotExpression() ::= "!" Expression()
       After: NotExpression() ::= "!" PrimaryExpression()

  [Updated on 3 May]:
  - Fix a bug in ArrayLookup().
     Before: ArrayLookup() ::= "[" PrimeExpression() "]"
     After: ArrayLookup() ::= "[" Expression() "]"

  - Fix a bug in PrimaryExpressionWithSuffix().
    Now "." and "[]" are treated as operators with highest precedence so that
    the following expressions are accepted

      x.f1().f2().f3()
      x.f4()[10]
      x.f4().length


syntaxtree/MainClass.java:
  Modified to include "VarDeclList" (for local variables declared in main().

visitor/BuildSymbolTableVisitor.java:
  Modified to add "main()" as an INSTANCE method to the main class (a hack).
  Declared local variables are attached to the main() method.

visitor/DepthFirstVisitor.java:
visitor/TypeDepthFirstVisitor.java:
  (Both) Modified to also visit the local variables declared in main()

visitor/PrettyPrintVisitor.java:
  Modified to also visit the local variables declared in main()

visitor/TypeCheckExpVisitor.java:
  Fixed some error messages

visitor/TypeCheckVisitor.java:
  Modified to also visit the local variables declared in main()
  Fixed a bug (visit(ArrayAssign))



Note:
Most of Java source files in visitor/ and syntaxtree/ were originally obtained from
http://www.cambridge.org/resources/052182060X/

minijava.jj was originally obtained from
http://www.cambridge.org/resources/052182060X/lecturers/default.htm