Bilkent CS315 Project

The project aimed to design and implement a programming language using Lex and Yacc. The language was designed to be a simple, yet powerful, language with a unique syntax and functionalities. The project involved creating a lexer and parser for the language, as well as implementing a code generator to execute the code. It features a familiar, readable syntax that eases the learning curve for new users while providing seasoned programmers with the tools they need to write efficient, error-free code.

Features

Zero Tolerance for Null Inputs: The language introduces a novel approach to input validation, ensuring that programs are robust against null or invalid inputs right from the get-go.

x := input "Enter value for x: ";
while (x == 0) begin
  display "Please enter a non-zero value for x";
  x := input "Enter value for x again: ";
end

Functionality and Flow Control: Clear, concise function definitions and flow control mechanisms, making code more readable and maintainable.

foo(p, q) : largest begin
  display "Function foo with parameters", p, "and", q;
  if (p > q) then largest := p else largest := q;
  return largest;
end

Iterative Processing and Data Handling: The language supports sophisticated data structures and iteration patterns, enabling developers to handle complex data manipulation tasks efficiently.

a := [12, 13, 14, 15, 16, 17];
sum := 0;
for (i := 0; i < length(a); i := i + 1) begin
  sum := sum + a[i];
end
display "Sum of array:", sum;

Example Programs

Program 1: Input Validation and Error Handling

x := input "enter value for x: ";
while (x == 0) begin
  display "please enter a non-zero value for x";
  x := input "enter value for x again: ";
end else begin
  display "value of x was correct in inital input";
end

y := input "enter value for y: ";
while (y == 0) begin
  display "please enter a non-zero value for y";
  y := input "enter value for y again: ";
end else begin
  display "value of y was correct in inital input";
end

z := input "enter value for z: ";
while (z == 0) begin
  display "please enter a non-zero value for z";
  z := input "enter value for z again: ";
end else begin
  display "value of z was correct in inital input";
end

display x, " times ", y, " times ", z;

Program 2: Function Definition and Invocation

foo(p,q) : largest begin
  display "my name is foo and my parameters are\n";
  display "p = ", p, ", q =", q, "\n";
  if (p>q) begin
    largest := p;
  end else begin
    largest := q;
  end
  return largest;
end

a := [5,0,3,-7];
b := [9,-2,-1];
for (i := 0, i < a.length(), i := i + 1) begin
  for (j := 0, j < b.length(), j := j + 1) begin
    c := foo(a[i],b[j]);
    display "c = ", c, ", a = ", a[i], ", b = ", b[j];
  end
end

Program 3: Iterative Processing and Data Handling

a := [12,13,14,15,16,17];
sum := 0;
for (i := 0, i < a.length(), i := i + 1) begin
  sum := sum + a[i];
end

display "sum of array is: ", sum;

Program 4: Sorting an Array

get_max(a,b):largest begin
  if (a > b) begin
    largest := a;
  end else begin
    largest := b;
  end
  return largest;
end

arr := [25,6,36,2,425,26,13];
for (i := 0, i < arr.length(), i := i + 1) begin
  for (j := i + 1, j < arr.length(), j := j + 1) begin
    if ( max(arr[i], arr[j]) != arr[j] ) begin
      temp := arr[i];
      arr[i] := arr[j];
      arr[j] := temp;
    end
  end
end

display "[ ";
for (i := 0, i < arr.length(), i := i + 1) begin
  display arr[i], ", ";
end
display " ]\n";

Program 5: Inline Functions and Expressions

get(a):d begin

  d := input "calculating d";  /* inline*/
  display "value of d: ", d; 
  return d; /* inline */
end

b := a + 2 + get(5) * 10; /* inline */
a := input "enter a value for a: ";
arr := [12,13,14];
b := arr.size();
c := arr[2];
while (a > 12) begin
  a := a - 1;
end else begin
  display "a was greater than 12";
end
for (i := 1, i < 10, i := i + 1) begin
  display "test";
end

The source code for the project can be found on GitHub

Programming Language in Lex and Yacc