COP 4620/5625 - Programming Language Translators


          Project Three - More Extensions to Tiny


Add the following constructs to Tiny:

     1)   The 'char' data type.

     2)   Constant definitions, a la Pascal, e.g.,

                          const   Three = 3;
                                  F = 'f';
                                  T = true;


     3)   The user enumerated type definition. Example:


                 type Color = (red,white,blue);

     The  intrinsic  type  'boolean'  should  also  be   re-
     implemented,  as  if it were an enumerated type.  Also,
     allow for 'synonym' definitions, so that one type  name
     is  synonymous  with  another.   If used in conjunction
     with scopes, type name swapping can take place:



                    type A = integer;
                         integer = boolean;
                         boolean = A;


     4)   For enumerated types, use the LIMIT instruction to
          produce  run-time  errors  if  a  value  is out of
          range.  The LIMIT instruction has no operands, and
          it  operates  as  indicated  in  the  C code shown
          below. In fact, this IS the code for LIMIT, in the
          interpreter.

                 case LIMITOP : temp2 = PopLf();  /* U */
                                temp1 = PopLf();  /* L */
                                temp  = PopLf();  /* X */
                                if ((temp >= temp1) && (temp <= temp2))
                                  PushLf(temp);
                                else {
                                  fprintf(output,"<<< MACHINE ERROR >>>: ");
                                  fprintf(output,"VALUE OUT OF RANGE0);
                                  DumpMemory(output);
                                  FatalError();
                                 }
                                 break;

     5)   The intrinsic functions "succ", "pred"  and  "ord"
          (for   integers   and  characters  and  enumerated
          types), and "chr" to move from integers to charac-
          ters.

     6)   Change the way input is done  in  Tiny,  from  the
          intrinsic,  parameterless  function "read", to the
          "read" statement, a la Pascal.   In  other  words,
          input is to be done with statements such as

                          read(a,b,c,x,y,z)

          Each of the arguments of "read" must  be  a  vari-
          able,   of  type  integer  or  character.  Each of
          the variables is read from a  separate   line   on
          the   input.    Two   new machine instructions are
          available for this:

                            SOS   INPUTC
                            SOS   OUTPUTC


     7)   Allow output of both integers and  characters,  as
          in
                  output('a','=',' ',a,' ',b,3,'x')

          Also, allow string literals, but only in the  out-
          put statement.  For example,

                     output ("a's value is ", a)



For this assignment, you will implement  identifier "modes".
Details in class.


DUE DATE:  Friday, November 16.