Let me ask the question slightly differently. Without constraining yourself to legal Julia syntax, what would you like to go in, and what do you want to come out? I get the feeling there's a design here that doesn't have this complexity--my intuition is that a generic function can be used to drive this just fine (called within a macro to facilitate the final splice.) But that's still hard to concretely suggest.
On Saturday, April 4, 2015 at 9:39:57 PM UTC-5, Abe Schneider wrote: > > I don't understand how what I'm trying to do falls outside the domain of > transforming code. My main goal is to take a user-defined grammar and > create relevant code. > > More to the point, I think the general ability to generate expressions > based on functions/namespaces is also solidly in the domain of transforms. > I can imagine plenty of use-cases for language-bindings, communication, etc. > > Yes, there are many simple macros one can create, which are useful, but > there exists many useful things one can do with macros that can get more > complex. > > A > > On Saturday, April 4, 2015 at 10:11:25 PM UTC-4, Jameson wrote: >> >> I think the underlying issue may be that you are trying to have the macro >> do too much, when you should instead be just doing source-code transforms >> and preprocessing. One such example of a great use of a macro is simply: >> >> macro special_foo(syntax_tree) >> return quote >> special_foo( $(QuoteNode(syntax_tree) ) >> end >> end >> >> >> On Sat, Apr 4, 2015 at 8:05 PM Abe Schneider <abe.sc...@gmail.com> wrote: >> >>> The issue I'm dealing with is that I have a macro that I want to pass a >>> list of functions that the macro can employ for parsing grammars. The macro >>> itself exists already, and it currently has its own static list of >>> functions. I'm trying to figure out a way to allow the user of the library >>> to customize it. >>> >>> For example: >>> @grammar foo begin >>> start = list(integer, r", ") >>> end >>> >>> where `list` is a user supplied function. The issue that I keep running >>> into is that there doesn't seem to be any easy way of just passing in a >>> function to a macro. Turning an expression into a function is problematic, >>> because `eval`s are: (a) only work in the modules namespace, and (b) are >>> frowned on. >>> >>> I've thought about manually looking up the symbol name in the various >>> namespaces, but while I've found methods to list the functions, I haven't >>> found a way to do the reverse. >>> >>> Ideally, it would be nice to generate an expression with `call` that >>> took a symbol and a namespace, that way no lookups would have to be done. >>> >>> Having hit a dead end in this direction, it occurred to me that it might >>> be possible to do something like this: >>> @set_parsers(list, etc) >>> @grammar foo begin >>> ... >>> end >>> >>> >>> where '@set_parsers` would generate the `@grammar` macro with the static >>> list it already has plus whatever else the user adds in. >>> >>> Which works, except for the whole module issue. >>> >>> >>> Thanks, >>> A >>> >>> >>> On Saturday, April 4, 2015 at 12:41:27 PM UTC-4, Patrick O'Leary wrote: >>>> >>>> On Saturday, April 4, 2015 at 9:04:10 AM UTC-5, Abe Schneider wrote: >>>>> >>>>> I should start off, not entirely sure this is an okay thing to do with >>>>> Julia. Suppose I want to create a macro that generates another macro... >>>>> >>>> >>>> I'm not sure whether this should work or not, but either way I'm not >>>> sure how it's any more expressive than macros alone? Can you describe what >>>> it is you want to do at a high level in a little more detail? There might >>>> be another way. >>>> >>>
