LangX041

LangX041 is a small programing language (nano-programing language) with syntax inspired by Java, Python, JS, and C++ and runs on JVM. In the current version, LangX041 can perform arithmetic and conditional operations on integers.

Tokens and Keywords

• Comment - Currently only single line comment is supported. As in Python, use # for adding comment. For example, # this is a comment
• Statement Termination - Use dot operator(.) for statement termination.
• Importing - Use require to import Java libraries. For example, require java lang. to import all classes of java.lang
• Variable Declaration - Use let keyword, as in JS, for variable declaration. For example, let var = 9.
• Condition - Classical if condition can be used whose syntax is as shown.

      if 2 > 1 do
          # do something
      stop
  

• Looping - Loop can be created using the keyword loop_if. The syntax is as shown.

      loop_if 2 > 1 do
          # do something
      stop
  

• Mathematical Operations - Currently addition(+), subtraction(-), multiplication(*), division(/) and modulo(%) operations can be performed on integers.
• Mathematical Relations - Currently greater than(>), less than(<), equals to(==), greater than equals to(>=), less than equals to(<=) and not equals to(!=) operations can be performed on integers.
• Literals - Variable names can consist alphabet, number(0 to 9) and _ but cannot start with a number
• Executing Java Methods - We can ONLY execute public static methods in the formate ClassName::[Method|Members]( number ). For example, System.out.println() method used for printing output can be used as System::out::println(). The property of operator :: is taken from C++.

Code Execution

LangX041 is an interpreted language like Perl or Python. It can read a text (source code) from file and parse it to create an object tree for interpreting them i.e. executing instructions.

• Make sure you have JAVA installed in the system as JVM is required for executing instructions.
• Write your code as per the syntax of the language and save it in a file with extension as .lgx
• Use the JAR present in /JAR folder
• In command-line or terminal execute the JAR while passing the saved .lgx file as an argument.

Sample Code

Consider the following code of finding (even numbers from 0 to 50 ) - 6. Save it in a file named test.lgx

    # program to print required numbers
    require java lang.
    
    let var = 11.
    var = 0.
    
    loop_if var < 50  do
    	let tmp = 3.
    	if var%2 == 0 do
    	    System::out::println( var - tmp * 2 ).
    	stop	# if ends
    	var = var + 1 .
    stop	# loop ends

Execute the JAR file using the command java -jar langx041.jar test.lgx. The output of the execution is

-6
-4
-2
0
2
4
6
8
10
12
14
16
18
20
22
24
26
28
30
32
34
36
38
40
42

• Make sure to pass the proper path of the source file in the argument. In the sample shown both the JAR and test.lgx are present in the same folder
• The above code is shown just to highlight the syntax and features of the language. It can further be optimized.

Digging deeper

Tokens and grammars are the core of any language. They are used in the following parts of the compiler in order to execute given source code.

• Lexer - Converts source code to tokens. Implemented using regular expressions.
• Parser - Converts tokens into nodes (syntax trees) according to the grammar.
• Interpreter - Responsible for executing the generated nodes.
• Runtime - Can be procedural, class based, prototype based or functional.

In the design of LangX041, JavaCC is used as a lexar and parser generator. It is similar to yacc (another parser) in that it generates a parser from a formal grammar written in EBNF notation. It generates top-down parser, which limits it to the LL(K) class of grammar. Here LL(2) grammar is used for generating syntax tree using JTB (Java Tree Builder). Visit the official website of JavaCC for more information.

Java Reflection is used for making an interpreter of the language. The grammar and tokens of the language can be found in \src\langx041\MyNewGrammar.jtb file. Eclipse IDE has been used for the development purpose. See this link to know about the configuration of JavaCC in Eclipse

A new language can be designed in many languages e.g. Ruby (using Racc parser), Python (using Ply parser), Java (using JavaCC parser), C++, etc. There are also many lexar available e.g. Rex for Ruby, JFlex for Java, Ragel, etc. The use of Java for the design of LangX041 is just a choice. If a bug is found make sure to report.

License

MIT