stuff.sh

command {
  name = "ls",
  
  options = [
    Flag{ name = "long", short = 'l' },
    Flag{ name = "recursive", short = 'R', long = "recursive" },
    Option{ name = "block-size", long = "block-size", type = Int, default = None },
    Option{ 
      name = "color",
      long = "color", 
      type = < Always | Auto | Never >, 
      default = Some Always 
    }
  ],
  
  arguments = [
    { name = "files", type = List Filepath }
  ],
  
  type Output = 
    \opts -> 
    let
      FileEntry = 
        if opts.long
        then { 
          file : String, 
          owner : String,
          permissions : Permissions, 
          size : Int, 
          modified : Datetime
        }
        else { file : String }
      DirEntry = 
        if opts.long
        then {
          path : Filepath,
          count : Int,
          files : List FileEntry
        }
        else {
          path : Filepath,
          files : List FileEntry
        }
    in
      if opts.recursive
      then List DirEntry
      else List FileEntry
  
  program = 
    # type signatures can be omitted, but I've put them here for clarity
    \(opts : { 
        long : Bool, 
        recursive : Bool, 
        block-size : Int, 
        color : < Always | Auto | Never >
      }, 
      args : {
        files : List Filepath
      }
    ) ->
    if opts.recursive
    then 
      # IO (List DirEntry)
      if opts.long
      then do
        # IO (List {
        #   path : Filepath,
        #   count : Int,
        #   files : List { 
        #     file : String, 
        #     owner : String,
        #     permissions : Permissions, 
        #     size : Int, 
        #     modified : Datetime
        #   }
        # })
        
        result <- call("ls", [ "-l", "-R" ] ++ map toString args.files)
        
        # TODO: parse `result` and good error handleing
        _ result
      else 
        # IO (List {
        #   path : Filepath,
        #   files : List { file : String }
        # })
        _
    else
      # List FileEntry
      # etc.
      _ 
}

-----------------------------------

repl> :t ls -l
IO (List { 
  file : String, 
  owner : String,
  permissions : Permissions, 
  size : Int, 
  modified : Datetime
})