Recursive Descent Parser

Parser for a JavaScript-like language. Outputs a JSON abstract syntax tree (AST).

Example

./parse -e 'let x = 2 + 3;'

Output:

{
  "type": "Program",
  "body": [
    {
      "type": "VariableStatement",
      "declarations": [
        {
          "type": "VariableDeclaration",
          "id": {
            "type": "Identifier",
            "name": "x"
          },
          "init": {
            "type": "BinaryExpression",
            "left": {
              "type": "NumericLiteral",
              "value": 2
            },
            "operator": "+",
            "right": {
              "type": "NumericLiteral",
              "value": 3
            }
          }
        }
      ]
    }
  ]
}

Usage

# Enter your program inline
./parse -e '<your program>'

# Read your program from a file
./parse -f path/to/file

Language Features

• Math

  4 * (5 + 6) / 2;

• Variable declarations with no explicit typing

  let x, y = 10, z = "hello";

• Supported types: integer (123), string ("hello"), boolean (true/false), null

• Assignment

  x = 10;
  y += 2;

• Block scopes

  let x = 2;
  {
    let y = 3;
  }

• If-else statements

  if (x > 3) {
    y = 1;
  } else {
    y = 2;
  }

• Loops

  while (x < 3) {
    x += 1;
  }
  
  for (let i = 0; i < 3; i += 1) {
    x += i;
  }

How to Build

This project uses CMake.

mkdir build && cd build && cmake .. && make

The executable created is build/parse.

Run automated tests

Run build/run-tests. Tests are defined in tests folder.

Tests are also run on GitHub Actions runners using ubuntu-22.04 and macos-14.

Third Party Libraries used

• nlohmann/json