Custom Shells

A custom Molt shell is simply an application that:

  • Creates a Molt interp
  • Adds any desired commands by the methods described in the previous section
  • Passes the interp to molt_shell::repl (for an interactive shell)
  • Passes the interp and a file to molt_shell::script

The sample Molt application provides a full example; here's a sketch:

fn main() {
    use std::env;

    // FIRST, get the command line arguments.
    let args: Vec<String> = env::args().collect();

    // NEXT, create and initialize the interpreter.
    let mut interp = Interp::new();

    // NOTE: commands can be added to the interpreter here, e.g.,

    // Add a single module
    interp.add_command("hello", cmd_hello);

    // Install a Molt extension crate
    molt_sample::install(&mut interp).expect("Could not install.");

    // NEXT, evaluate the file, if any.
    if args.len() > 1 {
        molt_shell::script(&mut interp, &args[1..]);
    } else {
        molt_shell::repl(&mut interp);

pub fn cmd_hello(_interp: &mut Interp,  _: ContextID, argv: &[Value]) -> MoltResult {
    // Correct number of arguments?
    check_args(1, argv, 2, 2, "name")?;

    println!("Hello, {}", argv[1].as_str());