let preferred_customer = customer.TotalPurchases > 10000 ?

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.

Is it crying for the 'why'?

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...

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

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.

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.

Maybe having a look at Specifications. by Eric Evans evans@acm.org and Martin Fowler fowler@acm.org

order_shipped_specification

new_order_specification

has_credit_specification

should_be_locked_up_specification

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

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

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

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

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.

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.