elvish-clone/TODO.md

Next steps

• Editor (edit)
  • Multiline editing
• Syntax (parse, eval)
  • Globbing?
  • Adopt value/address duality of $a, so that set a [] is written as set $a [] - like Perl, but unlike old shell or Tcl
  • Introduce the distinction of special forms vs. functions
• Code structure (eval)
  • STATIC ANALYSER AND TYPE CHECKER

  • Implement variable capturing of closures, so that the following sets $v:

    var $v
    { set $v 2 }
    

  • Implement control structures - as special syntax or high-order function?

  • Support evaluating script

  • Determine namespacing mechanism (importable modules; relationship of functions vs. external commands, variables vs. environmental variables)

• Failing/exception/error (eval)
  • Determine failing mechanism
    • Exception handling a la Python/Lua/...?
    • Error parallel to value a la Icon?
    • Error as return value a la golang?
    • Error as special $status variable a la old Shell?

  • Failing behavior of builtins; intermediate state:

    var (echo a | tee /tmp/a) b = 1
    

    Should arity mismatch be detected early and avoid the side-effect of writing /tmp/a? Should $a and $b be defined? (var is going to be a special form, needs another subtle example)

• Data semantics, data passing (eval)
  • Determine mutability (mutable tables like in conventional imperative languages, or immutable data structure a la clojure?)
  • Allow functions to declare and use channel I/O
• Unix process stuff
  • Signal handling
  • Simple job control: support suspending and resuming jobs; no need for too complex job control, the role is which is largely subsumed by screen/tmux today
• All the TODO, XXX and BUG's in source :)