TODO

TODO - Darius's original (2008) list

Key to column 1:
X - done
N - won't do it
? - dunno what Darius meant


X basic interface to the hosting C program
X   (with wren_ prefixes & header file)

  better error reporting and recovery

  warn when memory gets low

  optional preloaded standard library
    (not in RAM -- I suppose we'd interpret the high bit of our 16-bit
    pointers as indicating it's in ROM space)

  write a bigger example, something vaguely useful

  fix remaining XXXs

  tauten and clean up the code

N optionally compile VM code into flash (I guess this'd obviate the 
N   separate ROM addressing, above)

X make it easier to add/remove primitives -- added CCALL

  improve safety in the face of pokes

? measure size of VM-compiled programs -- maybe Todd's "Nice little header" at end of boot.wren suffices?

  make VM encoding a bit more compact (the easy stuff)

  check for keyboard interrupt (or equivalent)

  basic debugging support
    * backtrace, at least
    * 'panic' primitive
    * decompiler?
  
X do something about (-1) as a literal? (parens ugly) - DONE - If last instruction is push, just negate.

  make 'else' clause optional? 

  require some end-of-function delimiter to reduce scope for ambiguity?
    (especially the treatment of newlines)
  
  a cleverer VM encoding vaguely along the lines of 'Little Smalltalk':
    * 4-bit split (opcode-family, parameter)
    * two 'misc' families with the opcode in the parameter part
    * extended-parameter families 
      (with 4-bit family code followed by 1- or 2-byte parameter value)
    * the obvious families like PUSH, FETCH_LOCAL, BRANCH, JUMP
    * the remaining space can go to combined superinstructions
      (interpreted from a 16-byte table for each such family; the
      peephole optimizer uses the same tables)
  along with:
    a 2-pass compiler, comprising:
      * parse and generate intermediate code forwards
        (intermediate code is pretty much like the current simple instruction
        set, but designed to be read only from the end backwards)
      * peephole-optimize backwards, converting to actual VM code
      * (and finally, memmove() the VM code into place; it will have shrunk)
    a self-hosted compiler, to take advantage of the above
      (it should be smaller overall than the C-compiled compiler)
  syntax extensible at runtime, using the above

  closures allocated into the dictionary, a la Forth's CREATE DOES>

  nested 'let' and 'fun'