All:
    - multi-line read
    - loop/recur ?
    - hash-maps with non-string keys
    - hash-map with space in key string (make)
    - keyword type
    - gensym reader inside quasiquote

    - per impl tests for step5_tco (if possible)
    - regular expression matching in runtest
    - Print full exception when test gets EOF from expect

    - Break out impl eval into step0.5
    - Fix quasiquoting of vectors

    - Get self-host working at earlier step:
        - Move try* to step6
        - Remove macros from mal

    - Implement/fix interop: C#, Java, Mal, PHP, Postscript, Ruby

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

Bash:
    - explore using ${!prefix*} syntax (more like make impl)
    - GC

C:
    - come up with better way to do 20 vararg code
    - GC

C#:

Clojure:

Go:
    - consider variable arguments in places where it makes sense
        https://gobyexample.com/variadic-functions

Java:
    - Use gradle instead of mvn
        http://blog.paralleluniverse.co/2014/05/01/modern-java/

Javascript:
    - interop: callbacks using Mal functions

Make:
    - allow '_' in make variable names
    - errors should propagate up from within load-file

Mal:
    - line numbers in errors
    - step5_tco

Perl:
    - fix metadata on native functions

PHP:

Postscript:
    - add negative numbers

Python:
    - error: python ../python/stepA_interop.py ../mal/stepA_interop.mal ../mal/stepA_interop.mal
    - interop tests

Ruby:


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


Future Implementations:

    - Rust:
        - http://doc.rust-lang.org/index.html
        - http://doc.rust-lang.org/intro.html
        - http://doc.rust-lang.org/guide.html
        - http://rustbyexample.com/index.html
        - http://www.rustforrubyists.com/book/index.html
        - http://pzol.github.io/getting_rusty/

        - http://featherweightmusings.blogspot.com/2014/05/rust-for-c-programmers-part-6-rc-gc-and.html
        - http://pzol.github.io/getting_rusty/posts/20140417_destructuring_in_rust/ (destructuring)
        - http://featherweightmusings.blogspot.com/2014/07/rust-for-c-programmers-part-8.html (destructuring)
        - http://featherweightmusings.blogspot.co.nz/2014/07/rust-for-c-programmers-part-9.html (destructuruing and matching)
        - http://blog.thiago.me/notes-about-rust-modules/
        - http://doc.rust-lang.org/std/io/io
        - https://github.com/shaleh/rust-readline/blob/master/src/lib.rs
        - http://stackoverflow.com/questions/23942627/does-rust-0-10-have-a-rl-package
        - http://blog.skylight.io/rust-means-never-having-to-close-a-socket/

    - Redmonk languages from Jan 2014:
        http://sogrady-media.redmonk.com/sogrady/files/2014/01/lang-rank-114-wm.png
    
        - Tier 1
            * JavaScript
            * Java
            * PHP
            * C#
            * Python
            - C++
            * Ruby
            * C
            - Objective-C
            * Perl 
            * Shell (Bash 4)

        - Tier 2
            - R
            - Scala
            - Haskell
            * Clojure
            - CoffeeScript
            - Visual Basic
            - Groovy
            - Go
            - Lua
            - Erlang
            - Emacs Lisp
            - Assembly
            - Scheme
            - FORTRAN
            - Dart
            - F#
            - D

        - Tier 3
            - TypeScript
            - Racket
            - HaXe
            - Pascal
            - VimL
                - https://github.com/tpope/timl
            - Common Lisp
            - Rust
            - M (OpenM/MUMPS)
            - Factor (Stack-based)

    - Others:
        - Forth (Stack-based)
        - BF (Crazy)
        - TeX/LaTeX
            - Basic interpreter in TeX: http://ctanhg.scharrer-online.de/pkg/basix.html
            - Cheat Sheet: http://www.stdout.org/~winston/latex/latexsheet.pd
            - latex '\nonstopmode\input' blah.tex