OOPsy-OOP Learning Language

Authors

Natalia Dybczak & Jagoda Flejmer

Contact

ndybczak@student.agh.edu.pl

jflejmer@student.agh.edu.pl

Goals

Creating an educational programming language aimed at helping young learners grasp object-oriented programming in an intuitive and accessible way. The project includes an interpreter and a compiler that translate the OOPsy language into equivalent Java code for execution or further compilation.

Implementation language

Python was chosen for its readability, simplicity, and widespread use in education. Python also offers robust support for building interpreters and compilers, including libraries for lexical and syntax analysis.

Scanner & Parser implementation

The scanner and parser will be implemented using ANTLR 4, a powerful parser generator that supports multiple target languages, including Python. ANTLR will be used to define the grammar of the language, from which it will automatically generate the lexer (scanner) and parser components. These components will then be integrated into the Python-based compiler.

Tokens

---

Data Types & Literals

Name	Regex	Description
TYPE_INT	int	Keyword for integer type
TYPE_FLOAT	float	Keyword for floating-point type
TYPE_CHAR	char	Keyword for character type
TYPE_STRING	string	Keyword for string type
TYPE_BOOL	bool	Keyword for boolean type
BOOL_LITERAL_TRUE	true	Boolean literal (true)
BOOL_LITERAL_FALSE	false	Boolean literal (false)
INT_LITERAL	[0-9]+	Integer literal
FLOAT_LITERAL	[0-9]+\.[0-9]+	Floating-point literal
CHAR_LITERAL	'[^\\]'	Character literal
STRING_LITERAL	".*?"	String literal

---

Operators

Name	Regex	Description
PLUS_OPERATOR	\+	Addition operator
MINUS_OPERATOR	-	Subtraction operator
MULTIPLY_OPERATOR	\*	Multiplication operator
DIVIDE_OPERATOR	/	Division operator
MODULO_OPERATOR	%	Modulo operator
INCREMENT_OPERATOR	\+\+	Increment operator
DECREMENT_OPERATOR	--	Decrement operator
ASSIGNMENT_OPERATOR	=	Assignment operator
ADDITION_ASSIGNMENT_OPERATOR	\+=	Addition assignment
SUBTRACTION_ASSIGNMENT_OPERATOR	-=	Subtraction assignment
MULTIPLICATION_ASSIGNMENT_OPERATOR	\*=	Multiplication assignment
DIVISION_ASSIGNMENT_OPERATOR	/=	Division assignment
EQUAL_OPERATOR	==	Equality check
UNEQUAL_OPERATOR	!=	Inequality check
GREATER_OPERATOR	>	Greater-than operator
LESSER_OPERATOR	<	Less-than operator
GREATER_EQ_OPERATOR	>=	Greater-or-equal operator
LESSER_EQ_OPERATOR	<=	Less-or-equal operator
AND_OPERATOR	&&	Logical AND operator
OR_OPERATOR	||	Logical OR operator

---

Symbols & Separators

Name	Regex	Description
LEFT_BRACKET	\[	Opening square bracket
RIGHT_BRACKET	\]	Closing square bracket
LEFT_PARENTHESIS	\(	Opening parenthesis
RIGHT_PARENTHESIS	\)	Closing parenthesis
LEFT_BRACE	{	Opening curly brace
RIGHT_BRACE	}	Closing curly brace
DOT_SEPARATOR	\.	Dot separator (e.g., for methods)
COMMA_SEPARATOR	,	Comma separator
COLON_SEPARATOR	:	Colon separator
SEMICOLON_SEPARATOR	;	Semicolon end of statement

---

Comments & Whitespace

Name	Regex	Description
LINE_COMMENT	//.*	Single-line comment
BLOCK_COMMENT	/\*.*?\*/	Multi-line comment
WHITESPACE	[ \t\r\n]+	Whitespace (to be skipped)

---

OOP Keywords

Name	Regex	Description
CLASS_KEYWORD	class	Keyword to define a class
MAIN_KEYWORD	main	Entry point of the program
INHERITS_KEYWORD	inherits	Keyword to declare inheritance
HAS_ATTRIBUTE_KEYWORD	has	Keyword to declare attributes
METHOD_KEYWORD	method	Keyword to declare methods
CONSTRUCTOR_KEYWORD	constructor	Keyword to define constructor
CREATE_KEYWORD	create	Keyword to instantiate objects
OF_STATEMENT	of	Used in constructs like create X of Y
SELF_KEYWORD	self	Reference to current object
ABSTRACT_KEYWORD	abstract	Declares a class or method as abstract
FINAL_KEYWORD	final	Declares a class or method as non-inheritable
OVERRIDE_KEYWORD	override	Indicates method override
SUPER_CALL	super	Call to parent class method
PUBLIC_MODIFIER	public	Public access modifier
PRIVATE_MODIFIER	private	Private access modifier
LIST_TYPE	list	Declares a list type
DICTIONARY_TYPE	dict	Declares a dictionary type

---

Control Flow Keywords

Name	Regex	Description
PRINT_KEYWORD	print	Keyword for printing values
IF_KEYWORD	if	Conditional keyword
ELSE_KEYWORD	else	Alternate branch keyword
REPEAT_KEYWORD	repeat	Loop keyword
UNTIL_KEYWORD	until	Loop exit condition keyword
FOR_KEYWORD	for	For-loop keyword
IN_KEYWORD	in	Membership or iteration keyword
DO_KEYWORD	do	Loop body start keyword
INPUT_STATEMENT	input	Keyword to read user input
RETURN_STATEMENT	return	Keyword for returning from a function
BREAK_STATEMENT	break	Keyword to exit a loop early
CONTINUE_STATEMENT	continue	Keyword to skip to next loop iteration

---

Identifiers

Name	Regex	Description
IDENTIFIER	[a-zA-Z_][a-zA-Z0-9_]*	Keyword for printing values

Sample Code

class Animal {
    has name: string;
    has age: int;

    method speak() {
        print("I am an animal.");
    }
}

class Dog inherits Animal {
    has breed: string;

    method speak() {
        print("Woof!");
    }

    method describe() {
        print(self.name);
        print(self.age);
        print(self.breed);
    }
}

method main() {
    create myDog of Dog;
    myDog.name = "Burek";
    myDog.age = 5;
    myDog.breed = "Labrador";

    if myDog.age > 3 {
        myDog.speak();
    } else {
        print("Too young to bark.");
    }

    repeat {
        print(myDog.name);
        myDog.age = myDog.age + 1;
    } until myDog.age > 6;

    return;
}

Grammar

This project uses ANTLR 4 for lexical and syntactic analysis.

The grammar is defined using two files:

• OOPsyLexer.g4 – defines tokens (keywords, operators, literals, etc.)
• OOPsy.g4 – defines parser rules (program structure, statements, expressions)

Exception and error handling

Errors (semantic) are handled by program semantic_checker.py by static iteration over the code. Example programs resulting in errors are placed in errors directory.

GUI

Graphical user interface allows the user to type code in OOPsy and receive the same programme in Java as well as interpreted output. It also returns error message in case of an issue. The code is located gui.py file.