#tonyfettes/starlark

#Features

• Core Starlark types: None, bool, int, string, list, tuple, dict
• Functions with closures, default parameters, *args, and **kwargs
• List/dict comprehensions
• 25+ built-in functions (len, range, sorted, enumerate, zip, ...)
• 50+ methods on strings, lists, and dicts
• Module loading via host-provided callback
• Custom built-in functions for host integration
• 660+ tests including conformance tests against starlark-go

#Usage

{
  "deps": {
    "tonyfettes/starlark": "0.1.0"
  }
}

#Evaluate a module

let env = @starlark.new_environment()
let globals = @starlark.eval(
  #|def greet(name):
  #|    return "Hello, " + name + "!"
  #|message = greet("MoonBit")
  ,
  environment=env,
)
println(globals["message"]) // String("Hello, MoonBit!")

#Evaluate an expression

let env = @starlark.new_environment()
let result = @starlark.eval_expr("[x * x for x in range(5)]", environment=env)
println(result) // List({val: [Int(0), Int(1), Int(4), Int(9), Int(16)]})

#Register custom built-in functions

let env = @starlark.new_environment()
@starlark.set_builtin(env, "double", fn(args, _kwargs) {
  match args[0] {
    @value.Value::Int(n) => @value.Value::Int(n * 2L)
    _ => fail!("expected int")
  }
})
let globals = @starlark.eval("result = double(21)\n", environment=env)
println(globals["result"]) // Int(42)

#Load modules

let loader : (String) -> String raise Error = fn(mod) {
  if mod == "math.star" {
    "pi = 3  # int-only, no floats\ndef square(x):\n    return x * x\n"
  } else {
    fail!("module not found: " + mod)
  }
}
let env = @starlark.new_environment(loader=Some(loader))
let globals = @starlark.eval(
  #|load("math.star", "square")
  #|result = square(7)
  ,
  environment=env,
)
println(globals["result"]) // Int(49)

#Starlark Spec Coverage

#Architecture

Source String -> Lexer -> Tokens -> Parser -> AST -> Evaluator -> Value

#Development

moon check          # Type check
moon test           # Run all tests
moon fmt            # Format code
moon test --update  # Update snapshot expectations

#License