Ayende @ Rahien

pb commented on Challenge: Don't stop with the first DSL abstraction

Fri, 05 Sep 2008 01:56:38 GMT

C#: The ultimate DSL rules engine It seems somewhat simple to split things up to make a fluent interface in C# that makes sense. But this is much more work.

Ayende Rahien commented on Challenge: Don't stop with the first DSL abstraction

Thu, 04 Sep 2008 17:02:19 GMT

See the next post to see how I think we can introduce it. A scenario with actions based on this scenario is actually very easy to explain

Avish commented on Challenge: Don't stop with the first DSL abstraction

Thu, 04 Sep 2008 16:45:14 GMT

From your reply to Gilligan, I reckon that you think this snippet should convey chunked concepts like "preferred customers get 5 percent discount and extra credit" and "regular customers don't get no discount and we set feds after 'em soon as they try to f*ck with us". I'm not sure the users of this DSL will be able to grok the non-trivial concept of introducing new "thingies" into the DSL, and using them later. That's a very code-ish concept: declaration and usage.

Ayende Rahien commented on Challenge: Don't stop with the first DSL abstraction

Thu, 04 Sep 2008 16:34:38 GMT

That is just playing with the syntax, and not really changing the abstraction

Tobin Harris commented on Challenge: Don't stop with the first DSL abstraction

Thu, 04 Sep 2008 16:32:03 GMT

How about the ability to vary the language to make it read more naturally? This might mean adding synonyms. Also, you could have "fluff" keywords that make it read better but which are ignored by the interpreter. This could be a totally *terrible* idea, I'm just thinking out loud :) Example: when a bounced_check arrives or refused_credit: if customer.TotalPurchases > 10000: # preferred ask_authorizatin_for_more_credit otherwise call_the cops when a new_order arrives: if customer.TotalPurchases > 10000: # preferred apply_discount of 5.precent when order_shipped happens: send_marketing_stuff unless the customer.RequestedNoSpam Synonyms else => otherwise Ignored Words (fluff keywords) a arrives the of happens

Ayende Rahien commented on Challenge: Don't stop with the first DSL abstraction

Thu, 04 Sep 2008 15:49:17 GMT

Gilligan, I _hate_ the syntax, but you got the right idea

Gilligan commented on Challenge: Don't stop with the first DSL abstraction

Thu, 04 Sep 2008 15:48:05 GMT

Perhaps something roughly like this (excuse any bad syntax): def: preferred_customer_status payment_failed = ask_authorization_for_more_credit discount = 5.percent end def def: regular_customer_status payment_failed = call_the_cops discount = 0.percent end def Then you would apply the rules as such: if customer.TotalPurchases > 10000: customer_status = preferred_customer_status else: customer_status = regular_customer_Status upon bounced_check or refused_credit: customer_status.payment_failed upon new_order: apply_discount customer_status.discount upon order_shipped: send_marketing_stuff unless customer.RequestedNoSpam

Ayende Rahien commented on Challenge: Don't stop with the first DSL abstraction

Thu, 04 Sep 2008 14:38:48 GMT

Joseph, Your approach is somewhat better, but still suffers from the same fundamental issue

Joseph Gutierrez commented on Challenge: Don't stop with the first DSL abstraction

Thu, 04 Sep 2008 14:32:51 GMT

Try this: ask_authorization_for_more_credit with preferred upon bounced_check or refused_credit: call_the_cops without preferred upon bounced_check or refused_credit: apply_discount 5.precent with preferred upon new_order send_marketing_stuff unless customer.RequestedNoSpam upon order_shipped

Bunter commented on Challenge: Don't stop with the first DSL abstraction

Thu, 04 Sep 2008 13:27:38 GMT

If number of rules grow, this DSL will be long as the river of amazon.

James commented on Challenge: Don't stop with the first DSL abstraction

Thu, 04 Sep 2008 13:19:45 GMT

Maybe having a look at Specifications. by Eric Evans and Martin Fowler order_shipped_specification new_order_specification has_credit_specification should_be_locked_up_specification

Gilligan commented on Challenge: Don't stop with the first DSL abstraction

Thu, 04 Sep 2008 13:03:57 GMT

I have no experience with DSLs, but I sense something there I cannot quite wrap my brain around. Some things that I would toy around with: 1) bounced_check and refused_credit could probably be combined into some sort of payment_failed object or state on the order. 2) I would really like to keep things focused on the order instead of both the customer and the order, like Benny mentioned. Perhaps setting a "doNotSendMarketingStuff" property on the order (this would also allow you to track the history of a customer's "nospam" setting, to a point). Actually, I do not even like my second point. I am back to square one.

Benny Thomas commented on Challenge: Don't stop with the first DSL abstraction

Thu, 04 Sep 2008 10:51:39 GMT

I'm no DSL man, but this seems a bit odd: upon order_shipped: send_marketing_stuff unless customer.RequestedNoSpam Every other place you are using if, and suddenly you are using unless. Inkonsistence in my world. But i miss order handling stuff in your DSL, everything is about a customer, but nothing about the order.

John commented on Challenge: Don't stop with the first DSL abstraction

Thu, 04 Sep 2008 09:37:54 GMT

You saw cockroaches at Starbucks? Did you call the environmental services?

firefly commented on Challenge: Don't stop with the first DSL abstraction

Thu, 04 Sep 2008 06:39:49 GMT

the unless part? :) upon bounced_check or refused_credit: ask_authorizatin_for_more_credit unless IsNotPrefered call_the cops unless Prefered upon new_order: apply_discount 5.precent unless IsNotPrefered upon order_shipped: send_marketing_stuff unless customer.RequestedNoSpam This way it's more uniform = easier for a parsing engine... or even a gui...

Ayende Rahien commented on Challenge: Don't stop with the first DSL abstraction

Thu, 04 Sep 2008 04:51:41 GMT

Demis, As I mentioned, this is a valuable part, but not by far the most important thing.

Ayende Rahien commented on Challenge: Don't stop with the first DSL abstraction

Thu, 04 Sep 2008 04:49:06 GMT

Joao, No, I try no to do things twice.

Ayende Rahien commented on Challenge: Don't stop with the first DSL abstraction

Thu, 04 Sep 2008 04:47:29 GMT

Bob, If you click on the book link on the side bar, you will go to a site where you can buy a PDF copy of the pre release version.

João Bragança commented on Challenge: Don't stop with the first DSL abstraction

Thu, 04 Sep 2008 04:34:18 GMT

Is it crying for the 'why'?

Bob commented on Challenge: Don't stop with the first DSL abstraction

Thu, 04 Sep 2008 03:09:24 GMT

Is there anyway to get your pre-release copy of your "Building DSL in Boo"? I'm completely lost in DSL world, and it extremely lacks of resources out there.

Demis commented on Challenge: Don't stop with the first DSL abstraction

Thu, 04 Sep 2008 00:41:16 GMT

let preferred_customer = customer.TotalPurchases > 10000 ?