Re: [proto] Externalizing grammar pattern matching
On 11/23/2010 2:18 PM, joel falcou wrote:
> On 23/11/10 17:20, Eric Niebler wrote:
>> On 11/23/2010 10:19 AM, Joel Falcou wrote:
>>> So, question is: is there a way to have an extensible list of
>>> when that can be extended "from the outside", something
>>> like a proto::switch_ but with patterns instead of tag ?
>> No. The best you can do is document how to define a new Proto algorithm
>> from an old one:
>>
>>struct Old : proto::or_< ...> {};
>>
>>struct New : proto::or_< my_stuff, Old> {};
>>
>> Now everywhere in your library that you have the Old algorithm
>> hard-coded, you need to make it a template parameter so that your stuff
>> can be used with an extended algorithm.
> Can't the new extrnal_transform be of any help ?
No. You're not adding transforms. You're adding grammar rules. The
external transforms and proto::switch_ are extensible because they have
unique types off of which to key: rules and tags. There is no unique
type off of which to key in order to add new grammar rules. Phoenix uses
custom tag types with switch_. That's, or my above suggestion, are your
best bets.
--
Eric Niebler
BoostPro Computing
http://www.boostpro.com
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Re: [proto] Externalizing grammar pattern matching
On 23/11/10 17:20, Eric Niebler wrote:
On 11/23/2010 10:19 AM, Joel Falcou wrote:
So, question is: is there a way to have an extensible list of
when that can be extended "from the outside", something
like a proto::switch_ but with patterns instead of tag ?
No. The best you can do is document how to define a new Proto algorithm
from an old one:
struct Old : proto::or_< ...> {};
struct New : proto::or_< my_stuff, Old> {};
Now everywhere in your library that you have the Old algorithm
hard-coded, you need to make it a template parameter so that your stuff
can be used with an extended algorithm.
Can't the new extrnal_transform be of any help ?
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Re: [proto] Externalizing grammar pattern matching
On 11/23/2010 10:19 AM, Joel Falcou wrote:
> So, question is: is there a way to have an extensible list of
> when that can be extended "from the outside", something
> like a proto::switch_ but with patterns instead of tag ?
No. The best you can do is document how to define a new Proto algorithm
from an old one:
struct Old : proto::or_< ... > {};
struct New : proto::or_< my_stuff, Old > {};
Now everywhere in your library that you have the Old algorithm
hard-coded, you need to make it a template parameter so that your stuff
can be used with an extended algorithm.
--
Eric Niebler
BoostPro Computing
http://www.boostpro.com
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[proto] Externalizing grammar pattern matching
Here is some classical pattern matching using proto::or_ https://gist.github.com/711891 This is pretty canonical I guess (unless my proto-fu is rusting). As stated in the comments, my main concern is that adding new pattern->value rules need to edit or_<>. Also classical. For a long time it didn't bothered me until I needed to ship some code doing this AND wanting to be extended by random contributors to add new patterns. I brainstormed and conjured something like: https://gist.github.com/711895 (hold your horses on the crappiness of my MPL, it's a quick'n'dirty demo code trying to get around the fact that mpl::pair, for whatever silly reason, IS NOT a MPL RandomAccessSequence :| ) So it's slightly better. Now I dont have to touch the or_<>, just the mpl::vector. Close but no cigare. After some other hours, I found a way to make a MPL map look-a-like where the insertion is external: https://gist.github.com/711906 Alas, i can't find a way to put a decent mpl::iterator over this so both puzzles pieces fits. So, question is: is there a way to have an extensible list of when that can be extended "from the outside", something like a proto::switch_ but with patterns instead of tag ? My daydream being something akin to : https://gist.github.com/711914 So, now, I'll be grateful if you can answer this by some "you moron, use X" :D ___ proto mailing list proto@lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/proto
