[rules-dev] accumulate to acc

[Wolfgang Laun]

On 18 August 2011 19:27, Mark Proctor <mproctor at codehaus.org> wrote:

>  On 18/08/2011 18:17, Wolfgang Laun wrote:
>
> On 18 August 2011 18:38, Mark Proctor <mproctor at codehaus.org> wrote:
>
>> We are looking to tighten up accumulate, using a new keyword to
>> differentiate. It will use ; for separation, to follow a similar form to
>> a 'for' loop.
>>
>> acc( CE*;
>> <func>*;
>> <guard>? )
>>
>> so something like:
>>
>> acc( $o : Order();
>>         $min : min( $o.value ),
>>         $max : max($o.value);
>>         $min > 100 && $max < 100 )
>>
>
> Given that I can do this today using an eval after the accumulate CE:
> What's the big gain, as compared to the nuisance of yet another CE, with the
> need to document (which, traditionally, isn't done so eagerly) and teach and
> learn and getting it free of bugs?
>
> I find the above looks cleaner and easier to read, the more we can reduce
> the need for 'eval' the better. It is a common enough use case that I feel
> it is worth support.
>

Well, a condition that's never true isn't a good use case. Even after
repairing it, the example does not tell you *where *the min and max,
respectively, are. Apart from determining the exact value of mininimum and
maximum (which could easily be added, together with locating the containing
Order!)
   not Order( value <= 100 )
   not Order( value >= 200 )
is more descriptive that the rather procedural "for" hidden in the proposed
"acc".

Perhaps there are better use case; this one does not convince me.

-W





> Acc is used a lot for CEP use cases and we need a syntax that can compete
> succinctly with alternative approaches - if we look like a dog dinner, we'll
> lose out to alternative CEP syntaxes. The separation of the segments using
> ";" gives a clearer distinction too, and it's 'for' loop like nature should
> more natural to people new to the engine.
>
> Mark
>
>
> -W
>
>
>>
>> I have wondered if we could use pipes on our functions, to be able to
>> pass the results of one function into another - just not sure how that
>> will work or look yet.
>> func(...) in func(...)
>> func(...) | func(...)
>>
>> Mark
>>
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>>
>
>
>
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