elvish/TODO.md

Next steps

• Editor (edit)
  • Multiline editing
• Syntax (parse, eval)
  • Sigil as shorthand for function invocation
    • vim =yaourt is equivalent to vim (= yaourt)
    • Implement globbing as a sigil to avoid cluttering the lexical structure (which sigil to use?)
    • Sigils are lexically scoped (they are just functions after all)
    • A closed set of characters eligible as sigils
• 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)
• Value semantics and data passing (eval)
  • First class IO values
  • Immutable by default, a la Clojure
    • Believed to faciliate concurrency
    • Just makes more sense
    • But namespace and $env need to be mutable - $env as a namespace?
  • Allow functions to declare and use channel I/O
• 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)
• 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 :)