Basic Interpreter for C like language

Author: Orkhan Huseynli, BSIT 2018, "ADA" University

Steps implemented:

• Lexing - Process of tokenizing input string.
• Parsing - Process of analyzing token list given by Lexer and creating parse tree (AST). Used LL(k) parsing algorithm.
• TypeChecking - Checking if the program is well typed.
• Evaluation - Process of evaluting expression and statement.

Test codes that interpreter is able to process:

1. Basic if else evaluation

int main() {
  string name = "Orkhan"; string res;
  int privilege = 1;
  if (privilege == 0) {
     res = "Hello, " + name;
  } else {
     res = "you don't have privilege for the operation";
  }
  return res;
}

//Output: you don't have privilege for the operation

2. Basic while loop evalution

int main() {
  int count = 0;
  string res = "Iteration: ";
  while (true && count <= 10) {
    res = res + "," + count;
    count++;
  }
  return res;
}

//Output: Iteration: ,0,1,2,3,4,5,6,7,8,9,10

3. Basic eval error example

int main() {
  int x;
  int y;
  x = 12;
  return x + y;  
}

//Output: Variable y has never been initalized

4. Basic parse error example

int main() {
  int x;
  int y
  x = 12;
  return x + y;  
}

//Output: Parse error: Unexpected token IDENT at position {x} expected SEMICOLON

4. Basic type error example

int main() {
  int x = "myString";
  return x;
}

//Output: trying to assign string to integer

5. Basic boolean operations example

int main() {
  int z = 12;
  bool x = true && x > 12;
  return x;
}

//Output: true

6. Mixed test case:

int main() {
   int y = 1;
   bool isOk = true;
   string res = "";
   while (isOk) {
      y = y * 2;
      if (y > 100) {
         isOk = false;
         res = "Y is: " + y;
      } 
      else {
         isOk = true;
      }
   }
   return res;
}
//Output: Y is: 128