Am Dienstag, 9. April 2013 11:41:38 UTC+2 schrieb puzzler:
>
> On Tue, Apr 9, 2013 at 1:33 AM, Tassilo Horn <ts...@gnu.org
> <javascript:>>wrote:
>
>> Nice, but providing the grammar as a plain string looks somewhat
>> unnatural to me. Why not something like this (parser being a macro)?
>>
>> (def as-and-bs
>> (parser
>> S = AB* .
>> AB = A B .
>> A = "a" + .
>> B = "b" + .))
>>
>>
> I played around with that, but even if you suppress evaluation by using a
> macro, Clojure's reader makes strong assumptions about certain symbols.
> For example, it is standard in EBNF notation for {} to mean zero-or-more.
> But if you include {A B C} in your grammar using the macro approach,
> Clojure's reader will throw an error because it treats {} as a map and
> expects an even number of forms to follow. That was the main reason, but
> it also makes the notation much more sensitive to whitespace (for example,
> AB * versus AB*). Gradually, those little issues start making it look less
> and less like traditional notation. There's something really nice about
> just being able to copy and paste a grammar off of a website and have it
> just work.
>
>
What about something like this, a little like enlive does encode selectors?
(insta/parser :S [:AB :*] :AB [:A :B] :A ["a" :*] :B ["b" :*])
-billy.
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