Hi, what do you think about dsl version using map?
Nice Idea was proposed here
http://www.reddit.com/r/Clojure/comments/1djbio/growing_a_lanugage_with_clojure_and_instaparse/c9qwv4d
On Tuesday, April 9, 2013 12:41:38 PM UTC+3, puzzler wrote:
>
> 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.e., symbols denote non-terminals, strings denote terminals, and the
>> dot indicates the end of a rule.
>>
>> Bye,
>> Tassilo
>>
>
> 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.
>
> I understand where you're coming from, though. It definitely is part of
> the Clojure culture to avoid string representations for many kinds of data
> (e.g., SQL queries). We do accept it for regular expressions, and for
> things like #inst "2011-12-31T19:00:00.000-05:00", though, and that's the
> kind of feel I was going for. Would it be more psychologically palatable
> to type:
> #insta/parser "S = 'a' 'b'"
> rather than
> (insta/parser "S = 'a' 'b'")
> ?
>
> What do you think would be gained by making it a macro? From my
> perspective, a macro is essentially just a string that is being processed
> by the Clojure reader (and thus subject to its constraints). If the
> grammar were expressed in the way you propose, is it any easier to build up
> a grammar programmatically? Is it any easier to compose grammars? If
> anything, I think it might be harder.
>
> Thanks for the comments,
>
> Mark
>
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