args

import args

A small argument parser over env.args(). The functions are pure fn, not effect fn, so they can be called from an ordinary fn main.

Function	Signature
args.raw()	() -> List[String]
args.flag(name)	String -> Bool
args.option(name)	String -> Option[String]
args.option_or(name, fallback)	(String, String) -> String
args.positional()	() -> List[String]
args.positional_at(i)	Int -> Option[String]

args.raw() is env.args() verbatim, which does not include the program path — the first element is the user’s first argument.

import args

fn main() -> Unit = {
  let name = args.option_or("name", "world")
  if args.flag("verbose") then println("verbose mode")
  println("hello, ${name}")
}

$ almide run greet.almd -- --name=ada --verbose
verbose mode
hello, ada

Matching rules

flag(name) is true for the long form --name or the short form built from its first letter — flag("verbose") matches both --verbose and -v.

option(name) reads the long form only, in either spelling: --name=value or --name value. A short option with a separate value (-n value) is not recognised.

positional() returns the arguments that do not start with -. Because it filters rather than parses, the value of a --name value option stays in the list.

With no arguments at all, everything degrades quietly: raw() is empty, flag is false, option is none.

One open bug

Calling positional_at twice with different indices hangs on the wasm target (#903). Reading positional() once and indexing the list is a safe workaround.

Command-line arguments are unavailable in a browser sandbox; a WASI host such as wasmtime supplies them normally.