Compiler of a simple imperative language

Description

A program that compiles an imperative language into virtual machine code. More detailed language and machine specifications are included in the labor4.pdf file with some example code. The compiler is written in C++ and uses Flex and Bison.

At the moment the project is going through a renovation, as I have learned a lot more concepts about C++, clean code, design patterns and TDD since the creation of the project and the project is too cool to be left in the past.

Language specification

Quick tour through language specification:

• arithmetic operations are performed on natural numbers. The result of subtracting a larger number from a smaller one is 0. In addition, dividing by zero should give a result 0 and the remainder is also 0,
• language includes implementation of procedures: procedures cannot contain recursive calls, formal parameters are passed through references (IN-OUT), variables used in a procedure must be it's formal parameters or be declared inside the procedure, only procedures defined earlier in the program code can be called in a procedure, other procedures can be called only with variables defined in the current procedure,
• you can use IF and IF ELSE conditions, WHILE and REPEAT UNTIL loops,
• REPEAT UNTIL breaks when the condition is met and the loop will execute at least once,
• instruction READ takes the input from the user and assigns it to the specified variable and WRITE command prints out variable or constant value,
• variables and procedures identifiers are described by the regular expression [_a-z]+,
• lowercase and uppercase letters are distinguished,
• you can use [comments] in the code, which cannot be nested, More on the grammar of the language in the labor4.pdf file.

Example code:

PROCEDURE swap(a,b) IS
VAR c
BEGIN
  c:=a;
  a:=b;
  b:=c;
END

PROCEDURE gcd(a,b,c) IS
VAR x,y
BEGIN
  x:=a;
  y:=b;
  WHILE y!=0 DO
    IF x>=y THEN 
      x:=x-y;
    ELSE 
      swap(x,y);
    ENDIF
  ENDWHILE
  c:=x;
END

PROGRAM IS
VAR a,b,c,d,x,y,z
BEGIN
  READ a;
  READ b;
  READ c;
  READ d;
  gcd(a,b,x);
  gcd(c,d,y);
  gcd(x,y,z);
  WRITE z;
END

How to run the project

To use the project, you need to run the CMake for the compiler and then Makefile for the virtual machine (which are located in the main folder and the virtual-machine/), then go to the directory where the executable file was created and write some code, save it in ie. "test_file", run the compiler with ./SimpleCompiler {test_file} {output_file} which will generate machine code to the output file and the last step is to run the virtual machine executable with ./maszyna-wirtualna {output_file} command.

Quick overview of files and folders structure

Source

Source folder contains compiler code:

• CodeGenerator (contains machine code generator),
• Memory (code for virtual machine memory mockup with some extensions like procedures and more complex variables),
• Parser (Flex and Bison code),
• Variables (code for variable implementation).

Tests

Folder that contains example code for testing and code that should give errors.

VirtualMachine

Folder with virtual machine files and code.

Contributors

• Mateusz Gancarz - compiler code
• Dr Maciej Gębala - virtual machine and assignment