On 2/19/20 10:25 AM, Jonathan Spratte wrote:
> Hi,
> 
>> - Defining an environment that sets up active characters to emulate
>>   traditional BNF syntax is very concise, but comes at the cost of
>>   delimited arguments and catcode madness.
> 
> You could as well use a letter-by-letter parser that doesn't need altered
> category codes. Take a look at the pgf module `parser`. That's not `expl3`
> but could give you an idea on what's possible.
> 
> Best,
> Jonathan
> 

I've been *toying* for a long time (haven't gone very far) with the idea
of writing a parser generator, but I couldn't decide how powerful to
make it.  One option would be to support "parsing expression grammars"
(PEGs), which can be parsed in linear time using a packrat parser (but
use a lot of memory, possibly problematic).  Another option would be to
stick with more traditional things like LL or LR parser.  To be honest,
I don't know enough about parsers and what useful languages they cover
to decide.  Thoughts welcome.

Best,
Bruno