The new gg format is based on a BNF file which can be found in the `gg`
directory. The code for decoding `.gg` files has been refactored to
mirror that file. The result is more resilient parsing, better errors,
and a greater ability to extend the format in the future.
The new decoder is notable in that it does not use a lexer. Both lexing
and parsing are done in a single step.
The format syntax itself has also been modified. Rather than using
semi-colons everywhere, commas are used as separators in tuples.
Additionally the final comma/semi-colon is no longer required.
This commit is the result of many days of picking vm apart and putting
it back together again. The result is an implementation which separates
compile and runtime into separate steps, and which functions (more)
correctly in the face of recursion.
Pretty much all aspects of vm have been modified or deleted, so it's not
even really worth it to describe specific changes. Just pretend this is
the original implementaiton and the old one was never done.
Getting `recur` to work required adding an Operation argument to a bunch
of places in a really hacky way. I don't like it at all, but I'm also
kind of out of mental energy to figure it out properly. The fibonacci
demo in the README _works_, at least, though I don't think it's actually
tail recursive.
The base graph implementation has been moved into its own package,
`graph`, and been made fully generic, ie the value on each vertex/edge
is a parameterized type. This will allow us to use the graph for both
syntax parsing (gg) and runtime evaluation (vm), with each use-case
being able to use slightly different Value types.
The vm does what it needs to do (evaluate the result of passing an input
to an operatio, where the input and the operation themselves may have
sub-inputs/operations to evaluate), with many caveats/misgivings.
