CS712/CS812
Programming Project Part 1
Spring 1998

Use flex and bison to write a calculator program for bitwise integer calculations.

At the 75% level, your program should support

• The following operators:
  • (unary) bitwise complement: ~

  • (binary) left shift: <<
    (binary) right shift with sign extension: >>
    (binary) right shift with zero extension: >>>

  • (binary) bitwise AND: &

  • (binary) bitwise XOR: ^

  • (binary) bitwise OR: |

• The following constants:
  • decimal unsigned integer constants: e.g. 209

  • hexadecimal unsigned integer constants: e.g. 0x20A

The operators are listed in order of decreasing precedence. The shift operators all have equal precedence. All the operators are left associative except for the complement operator, which is right associative. These operators have semantics that are the same as the corresponding Java operators.

Your calculator should support 32-bit integers. Constants that do not fit in 32 bits should be flagged as errors.

Expressions may be parenthesized.

The calculator should accept from stdin a series of expressions, one per line. For each line, the value of the expression should be printed to stdout as 0x followed by eight hexadecimal digits (i.e. print the leading zeroes).

Blank lines should be ignored. Spaces and tabs should be ignored, as well. That is, they have no meaning except to separate tokens.

If an expression is entered that has a syntax error (structurally invalid), an error message should be issued and the parser should be synchronized at the next newline character. If an expression is entered that has a semantic error (e.g. constant too large), then issue the appropriate error message, internally patch the error (e.g. make a constant that is too large have value 0), and continue processing. The goal is to be able to detect multiple semantic errors per line.

At the 85% level, your program should support

• All the 75% functionality

• Variables:
  • Each variable contains one 32-bit value.

  • A variable's initial value is undefined.

  • A variable is referenced by its name, which must start with a letter, be made up of letters and digits, and be at most 32 characters long.

• An assignment operator (=):
  • It is a binary operator that takes a variable as its left operand and an expression as its right operand. If it does not have a variable as the left operand then an error message should be emitted.

  • It is of lower precedence than all other operators.

  • It is right associative.

  • The assignment operator produces a value, which is the value assigned.

At the 100% level, your program should support

• All the 75% and 85% functionality

• A conditional expression operator (?:):
  • It is a ternary operator that has the same semantics as in C.

  • Its precedence is just above that of the assignment operator.

  • It is right associative.

• An iterative expression operator (#):
  • It is a binary operator.

  • The left operand is the "body".

  • The right operand is the "condition".

  • The body is first executed and then the condition. If the condition evaluates to zero, then the value of the iterative expression is the value of the last execution of the body. If the condition evaluates to nonzero, then the execution of the body and the condition is repeated.

  • The operator has the same precedence as the conditional expression operator.

  • It is right associative.

Your program will be graded primarily by testing it for correct functionality. However, you may lose points if your program is not properly structured or adequately documented.

When ready, the public test files will be in ~cs712/public/proj1.

You can write your program in either C or C++. You must submit a Makefile (called "Makefile") so that we can conveniently build your programs. Your executable program should be called "proj1". Your program will be graded on alberti.unh.edu so be sure to test in that environment.

Your program should be submitted for grading from alberti. To turn in this assignment, type:
~cs712/bin/submit proj1 list of files to submit

Do not turn in any non-Ascii files (i.e. no object files, no executable files, etc.).

Submissions can be checked by typing:
~cs712/bin/scheck proj1

To receive full credit for the assignment, you must turn in your files prior to 8am on Monday February 9. Late submissions will be accepted at the penalty of 5% per day up to one week late.

Remember: as always you are expected to do your own work on this assignment.

Comments and questions should be directed to pjh@cs.unh.edu