Getting Started

RocketLang started as a complete implementation of MonkeyLang — the language built in Writing an Interpreter in Go — and has been extended since with features both useful and not so useful.

Latest Version

Quick Start

// Values carry methods.
name = "rocket-lang"
print(name.uppercase())       // ROCKET-LANG
print(name.split("-").size()) // 2

// Arrays and hashes, both with methods of their own.
crew = ["ada", "grace", "alan"]
print(crew.size())            // 3
print(crew.contains?("ada"))  // true

ages = {"ada": 36, "grace": 45}
print(ages["grace"])          // 45

// Functions are values, so they can be passed around.
double = def(n)
  return n * 2
end
print(double(21))             // 42

// Blocks close with `end`, and parentheses around a condition are optional.
foreach i, member in crew
  if i > 0
    print(i.to_string() + ": " + member)
  end
end

// Errors are values you can catch.
begin
  print(1 / 0)
rescue e
  print("caught: " + e.message())
end

Split a program across files with modules, and pull in someone else's with planets:

import "./helpers" as helpers

For longer programs, the examples directory has solutions to several Advent of Code puzzles.

Help

Launch RocketLang with -h or --help for an overview of the CLI.

$ rocket-lang -h
Usage: rocket-lang [flags] [program file] [arguments]
       rocket-lang planet <command>

Available flags:
  -e, --exec string   Runs the given code.
  -v, --version       Prints the version and build date.

Run a file, evaluate a snippet, or start a REPL with no arguments at all:

$ rocket-lang program.rl
$ rocket-lang -e 'print("hi")'
$ rocket-lang