SWX: your own language on Node.js with AST and cryptography

Building the SWX Scripting Language on Node.js: Architecture and Implementation

SWX is a scripting language built on Node.js that handles the full code processing pipeline: from lexical analysis to execution. The process involves a lexer, parser, and interpreter.

Source code → [Lexer] → Tokens → [Parser] → AST → [Interpreter] → Result

The lexer breaks code into tokens, supporting custom operators like >~ for comparison and =? for equality. The parser builds the AST, and the interpreter traverses the tree to execute nodes.

Lexer: Tokenizing the Code

The lexer (lexer.js) converts strings into a sequence of tokens. Example:

swx x = 42

Becomes: KEYWORD(swx) IDENT(x) ASSIGN(=) NUMBER(42).

Handling multi-character operators requires precedence: >= is recognized as a whole. Contextual modes resolve conflicts with identifiers in the HTML generator.

Parser and AST

The parser (parser.js) uses recursive descent to build the AST, respecting operator precedence. Example condition:

swx x = 10
sw x >~ 5 {
    wx "greater than five"
}

AST:

{
  "type": "IfStatement",
  "condition": {
    "type": "BinaryExpression",
    "operator": ">=",
    "left": { "type": "Identifier", "name": "x" },
    "right": { "type": "NumberLiteral", "value": 5 }
  },
  "body": [
    {
      "type": "PrintStatement",
      "value": { "type": "StringLiteral", "value": "greater than five" }
    }
  ]
}

Precedence ensures correctness: 2 + 3 4 evaluates as 2 + (3 4).

Interpreter: Executing the AST

The tree-walking interpreter (interpreter.js) implements handlers for nodes:

• IfStatement: Evaluate condition and select branch.
• ForLoop: Iterate by counter.
• FunctionDeclaration: Store in symbol table.
• BinaryExpression: Handle arithmetic and logic.

Syntax and Constructs

SWX features a unique syntax:

Variables and Output

swx name = "SlywerX"
swx age = 20
wx "Hi, {name}! You're {age} years old."

Conditions and Loops

• sw for if, with dr as else-if/else.
• xs 5 { ... } — loop N times.
• xw item in arr { ... } — foreach.
• xl condition { ... } — while with 1 million iteration limit.

Functions and Pattern Matching

sx add(a, b = 0) => {
    ws a + b
}

match status {
    case 200 => { wx "OK" }
    case 404 => { wx "Not Found" }
    default  => { wx "Unknown" }
}

Pipe operator |> chains functions: "hello" |> upper.

Cryptography

The #x module integrates Node.js crypto:

swx hash = #x.sha256("hello")
wx hash  // 2cf24dba5fb0a30e26e83b2ac5b9e29e1b161e5c1fa7425e73043362938b9824

swx encrypted = #x.aes_enc("secret data", "mykey")
swx decrypted = #x.aes_dec(encrypted, "mykey")

swx keys = #x.rsa_keys(2048)
swx signature = #x.rsa_sign("data", keys.private)
wx #x.rsa_verify("data", signature, keys.public)  // true

HTML Rendering

The sx> DSL generates HTML with CSS:

sx> "output/index.html" {
    @style {
        body   >> bg(#030810) color(#fff) font(Courier New, monospace)
        h1     >> color(#00e5ff) size(24px) bold uppercase
        .btn   >> bg(#00e5ff) color(#000) pad(10px 20px) pointer
    }
    @body {
        div.card >> {
            h1 >> "Hello from SWX"
            button.btn >> (onclick: "alert('works!')") { "Click Me" }
        }
    }
}

Supports nesting and attributes.

Implementation Challenges

• Parser Precedence: Recursive descent with Pratt parsing.
• Lexer Conflicts: Context for *~ and CSS.
• While Loops: Iteration limit to prevent hangs.
• Standard Library: Testing on unstable interpreter.

Key Takeaways

• Full stack: lexer, parser, interpreter on Node.js.
• Custom syntax with pipes, pattern matching, and crypto module.
• HTML DSL for markup generation.
• Safeguards against infinite loops and lexer conflicts.
• Version 7.0.0 with RSA and AES.

— Editorial Team