💬 ScriptLang

This is a simple scripting language written in C++17. This project was a way to improve my knowledge on developing programming languages, stack-based virtual machines and even C++. In fact, the goal of this project is not to create a fast and efficient scripting programming language, but to learn how to parse and compile source code and how to output detailed error messages when one of these steps fails.

defun fib(n) {
      if n <= 1 {
            return 1;
      }

      return fib(n - 1) + fib(n - 2);
}

print fib(9);

🌟 Language Features

• Global and local variables
• If statements
• While loop
• Functions
• Print statement
• Classical operators + exponentiation

🧮 Supported data types

• Nil
• Booleans
• Strings
• Numbers

Warning

This language don't have structs or similar constructs and don't support closures.

🌱 Installation

📜 Prerequisites

• g++ compiler
• make

⚒️ How to build the interpreter?

In your terminal run the following command to build the interpreter:

make

After running it, a build folder will be generated, where the scriptlang interpreter executable is located.

✍️ Language Grammar

declaration ::= function-decl
            | variable-decl

variable-decl ::= 'let' IDENTIFIER '=' expression ';'

function-parameters ::= '(' IDENTIFIER (',' IDENTIFIER)* ')'
function-decl ::= 'defun' IDENTIFIER function-parameters block

block ::= '{' declaration* '}'

statement ::= if-statement
          | expression-statement
          | while-statement
          | for-statement
          | break-statement
          | continue-statement
          | return-statement
          | block

print-statement ::= 'print' expression ';'
if-statement ::= 'if' expression block ('else' block)*
while-statement ::= 'while' expression block
break-statement ::= 'break' ';'
continue-statement ::= 'continue' ';'
return-statement ::= 'return' expression? ';'

expression-statement ::= expression ';'

expression ::= assignment 
assignment ::= IDENTIFIER '=' assignment | logic-or
logic-or ::= logic-and ('or' logic-and)*
logic-and ::= equality ('and' equality)*
equality ::= comparison (('==' | '!=') comparison)*
comparison ::= term (('>' | '<' | '<=' | '>=') term)*
term ::= factor (('+' | '-' factor)*
factor ::= unary (('*' | '/' unary)*
unary ::= ('-' | '+' | 'not') unary | exponent
exponent ::= call ('**' factor)*

call-arguments ::= expression (',' expression)*
call ::= primary ( '(' call-arguments+ ')'
primary ::= NUMBER_LITERAL 
        | STRING_LITERAL 
        | IDENTIFIER
        | 'true'
        | 'false'
        | 'nil'
        | '(' expression ')'

🔭 Resources

For this project I took inspiration from these projects:

• GitHub - google/closure-compiler: A JavaScript checker and optimizer.
• GitHub - wren-lang/wren: The Wren Programming.