open CS334

(**
 * This program takes the first input given to `dotnet run`
 * and attempts to parse and evaluate the expression.
 * This program should probably do a bit more input validation
 * and also provide a usage() message when things go wrong,
 * but it is intentionally minimal so that you can focus your
 * attention on the new ideas.
 *
 * Note that the course packet chapter on Evaluation also
 * discusses a version of pluslang with a slightly different syntax
 * than the one here, however, the two languages are still
 * very similar.
 *)
[<EntryPoint>]
let main args =
    let input = args[0]
    let ast_maybe = parse input
    match ast_maybe with
    | Some ast ->
        printfn "%A" ast
        let res = eval ast
        printfn "result: %d" res
    | None ->
        printfn "Invalid program."
    0