Compiler HWK#5 Due date: 2:20pm, June 14, 2007

Write a simple compiler to parse
a simple PASCAL-like expression language with 1-D array,
IF .. THEN .. ELSE, while loop, for loop and case statement.
Code generation in C-- (Version 2.3);

A sample program is as follows:

       INCLUDE filename

       PROGRAM program_name
          VAR %% beginning of variable declarations, optional
          x, y, z: INTEGER;
          a : REAL;
          b: ARRAY[-20..30] OF REAL; %% 61 elements
          ENDVAR
       BEGIN
          READ(y);
          x := (y + 3 * 4) - 5;
          IF (x >= -20) AND (x <= 30)
          THEN  BEGIN
                  a := 0.3;
                  b[x] := a;
                END
          ENDIF
          WRITE(y);
          WRITESP();
          WRITE(x);
          WRITELN() ;
       END

The definition of your language is as follows:

1. This language is case-sensitive with reserved words.

    1.0 <optional include headers> is epsilon or
         INCLUDE filename[1] %% each include statement must be in one line
         ....
         INCLUDE filename[n]

         The included file contains the definition of procedures.

         ProcedureName():ReturnType  ;
         ProcedureName(Type1 ID1,Type2 ID2,..., TypeN IDN):ReturnType;
         
    1.1 <main program def>
        PROGRAM name
         optional var decl
        BEGIN
         statements or blocks
        END
    1.2 <optional var decl> is epsilon or
        VAR
        ...
        ENDVAR

        VAR ... ENDVAR is a declaration of local variables which can be
        empty or completely missing.
        VAR ... ENDVAR must be before any statements and can have only
        one appearance.

    1.3  IF boolean-expression
         THEN block/statement
         ENDIF

         IF boolean-expression
         THEN block/statement
         ELSE block/statement
         ENDIF

    1.4 <block>
        BEGIN
	   statements or blocks
        END

        BEGIN and END starts and ends a block, respectively.

    1.5 boolean-expression:
         
           expression (> | < | = | <= | >= | <>) expression
           boolean-expression (OR | AND) boolean-expression
           NOT boolean-expression
        Precedence and Associativity for operators follow C.

    1.6 <statements>
       a. assignment of expressions, where expressions
          can have variables, real-constant,
          integer-constant, (, ), +, -, *, / and "uminus".
          assignment is ":=",
       b. input statement %% it's legal when sysio.h is included
          READ(single variable)
       c. output statements %% it's legal when sysio.h is included
          WRITE(single variable) ---  output a variable
          WRITESP()              ---  output a single space
          WRITELN()              ---  write a new line
          There may have spaces before, in between or after "()".
       d. Procedure call is in the form of %% declared in header files
              procedure_name()
          There may have spaces before, in between or after "()".
       e. The statement terminator is ";"

     1.7 
         precedence/associativity of operators same as C
     1.8 for loop
            FOR int-var := int-expression-1 TO int-expression-2 DO
               statement/block

            FOR int-var := int-expression-1 DOWNTO int-expression-2 DO
               statement/block
     1.9 while loop
            WHILE boolean-expression DO
               statement/block
     1.10 case statement
            CASE expression OF
            constant1: statement/block
            constant2: statement/block
            ...
            [optional] OTHERWISE: statement/block
            ENDCASE;
    
2. each line has at most one statement
   can have a blank line
   cannot have a null statement, ";"
3. Two different data types: INTEGER and REAL.
   3.1 Each occupies 4 bytes.
   3.2 No type conversion is allowed.
   3.3 Can have 1-D array of INTEGER or REAL
          x, y ,z : ARRAY[20..30] OF INTEGER;
          ...
          x[a] := y[3] + 20;

4. variable must be declared before its usage.
   variable/program names uses the rule as HWK4.
   However, the length of a variable name is 1024. There can have lots
   of variables. I expect you to use either hash table or
   balanced-binary search tree for symbol tables.
5. Anything after %% are comments until to the end of the line.
6. Must detect the following error and reports its line number(report all errors):
    a. invalid ID names
    b. undeclared variables
    c. duplicatedly declared variables
    d. mismatched data type
    e. undefined procedure.
    f. duplicatedly declared procedures
    g. invalid constant
    h. illegal syntax
7. Name your compiler "pascal-" and it should support -S and -o option:

    pascal- program.p -o prog %% generate an executable called prog and default is p.out
    pascal- -S program.p         %% generate an file contains the intermediate code in C-- 

Note:
     (1) TA will announce details for error handling later.
     (2) To submit your homework, use the software submission system 
           designed by TA. Read TA's web site for details.
     (3) You need to have LEX and YACC programs.
     (4) TA will announce rules for submitting homeworks.