* Nomenclature

Since this is my internal notes on what I'm working on with Digamma, I thought I'd add a quick set of notes:

- Digamma: my Scheme dialect.
- PreDigamma: a restricted subset of Digamma meant for easier compilation.

- Vesta: The C Reference implementation of Digamma; relatively fast, but not my main focus area any more
- Enyo: The original PreDigamma compiler (never written)
- E' (E-prime): the "test compiler that actually became the compiler"; wasn't meant to test ideas for Enyo, but grew too big
- Enyalios: a complete rewrite of E' to be more modular (uses an IR) and easier to modify (well structured & documented)
- Hydra: a stack based VM written in Digamma that can self-host
- Typhon: modified Hydra, meant to compile with Enyalios

* Runtime only

- *DONE*: Add support for #;(datum) comments
- *DONE*: port that to Hydra's runtime

* Vesta/Hydra

- engines
- current-input-port, current-output-port, current-error-port
- with-output, with-input, with-error
- get/set current-X-port

* Enyalios

- *DONE*: top level Symbol for procedures, added to lparams\["env"\]
- *DONE*: top level static snil, strue, &c.
- *DONE*: add static snil &c to top level Symbol
- *DONE*: add that top level Symbol to procedure calls
- closures in HOFs (HIGH 1)
- free analysis for closures (HIGH 1)
- Internally-defined procedure lifting (HIGH 1)
- Inlining
- typing ala Stalin (recursive union types, soft-typing/gradul-typing)
- named-let (HIGH 2)
- do-loops (I guess?)
- fix apply!
- *DONE*: (was actually an issue with set!) fix deeply nested let issue with if: (let ((foo 1)) (if (> foo 0) (set! foo 1) #v))
- letrec
- *DONE*: let\* fix (doesn't correctly pass rewritten vars from above)
- *DONE*: fix load
- define-c-syntax
- *DONE*: define-syntax (HIGH 0)
- IL->JS, IL->C++, IL->JAVA, IL->X86\_64, IL->SPARC
- support %c, define-alien for self-hosting runtimes.
- *DONE*: %include, %prim
- inline or lift
- if lift, do free analysis & closure conversion
- if an inner proc is used in _tail position_, inline it (maybe only if tail rec?)
- beter param shaddowing; no reliance on another var? no shaddowing
- optimize more primitives: (*DONE*)+ - / \* < > >= <=
- open code fnumeq similar to eq?
- PARTIALLY *DONE* (for +)possibly look into destructive parameter updates? (foo (+ i 1)) could be AINT(i) += 1
- *DONE*: This fails to work correctly: (let ((i 0)) (set! i 10)) \[test more; you can see it in Typhon. Could be only when it is nested in an if\]
- *DONE*: check in on this: (foreach (fn (x) (write (keys x)) (newline)) some-var). Apparently generates the wrong environment in the output C code
- add merge-dict! procedure. It should default to _not_ overwriting keys that exist in the destination dictionary. (merge-dict! src : DICT dest : DICT overwrite? :BOOL)
- fix (string), (vector) compilation in IL->C
- *DONE*: fix (if SOME-COND #v SOME-OTHER CODE) in non-tail position
- *DONE*: fix COND in non-tail position
- add exception system (SRFI-34 via longjmp/setjmp)

* Hydra/Typhon

- *DONE*: fix closures
- *DONE*: port closure fix to Typhon
- *DONE*: review user of map, and potentially replace with bespoke, Enyalios\-friendly equivalent (SAC)
- idea: what if, instead of defining a list of primitives, &c., we just code primitives iff there is no other hit in the env? Users could do (define car (fn ...)), but it would not require having "car" defined in the env; a lookup against car could just hit a "default handler" of sorts. 
- *DONE*: Detect errors on the stack
- *DONE*: Detect errors on the stack in Typhon
- *DONE*: Move "display" instruction to be a call procedure instruction; top of stack is number of parameters.
- *DONE*: fix `(0 '(1 2 3 4 5)) => 1` (i.e. inserting the opcode for CAR allows a user to run CAR)
- Fix `(define x '(primitive . 0)) (x '(1 2 3 4))` which returns `1`, aka it is able to run CAR (Sandbox escape 0)
- Fix `(define y '(procedure . "display")) (display 13)` which displays 13 & returns 13, aka is able to run procedures (Sandbox escape 1)
- For the above two sandbox escapes: maybe test with eq? which would ensure we're only running the values that were pre-allocated...
- For the above sandbox issues: wrap/tag user provided data with a USER tag; unwrap in all Hydra@vm at the right time (i.e. prior to call, but not for dispatch)
- The "eq?" version is better, I think, because it requires less memory overall; the tagged version requires each user value to be tagged, which is needlessly wasteful
- Core version without repl/read, for use with IL->JS
- Move stack from pair to vector with fixed size, stack pointer, &c. (testing)
- *DONE*: add define-syntax and syntax-expand to Typhon
- *WON'T*: add define-syntax and syntax-expand to Hydra
- add define-macro and macro-expand to Typhon
- *WON'T*add define-macro and macro-expand to Hydra
- *DONE*: Move dump from pair to vector with fixed size, stack pointer, &c. (testing)
- *DONE*: hydra@\{operand, instruction\} => simple syntax
- *DONE*: add BEGIN form to Hydra
- *DONE*: add BEGIN form to Typhon
- Verify complete language coverage between Vesta and Typhon
- Errors buried deep within compiled code can bubble to the surface much later. Checkout Aneris.ss for a test (e.g. a call to "type" within an if block, when Hydra doesn't have the "type" procedure in its environment will call the error to be swallowed until much later. boo).
- *DONE*: Fix SegFault in Typhon with (append '() 3)
- *DONE*: fix the \*tlenv\* define from Aneris.
- Delimited Continuations in Typhon
- *DONE*: Cut down on calls to `pairlength`; see [http://lojikil.com/d/lisp/typhon-prof-13SEP2013.txt this profile set]
- add FAST-ADD, FAST-SUB, &c instructions for integers? (+ x 6) could be ((env-load x) (fast-add 6)); cuts down on one while-loop iteration
- *DONE* Fix `syntaxmystery.ss` weirdness; derived from [https://code.google.com/p/ypsilon/issues/detail?id=107 this issue in Ypsilon]

* Eurydice

- linting
- C-stress-style file system checks
- formatting (ala gofmt)
- refactoring: if<=>cond, cond<=>case, with<=>let, define<=>define-syntax, &c.

* All

- SRFI-0/7, for supporting different loads, different FFIs, different low-level runtimes...
- Scheme48-style modules.
- define-syntax
- fix giant HACK that is SRFI-55 support (require) + Libraries currently
- better typing (ala Stalin) support