[rules-dev] accumulate to acc

[Mark Proctor]

On 19/08/2011 05:53, Wolfgang Laun wrote:
>
>
> On 18 August 2011 19:27, Mark Proctor <mproctor at codehaus.org 
> <mailto: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
>>     <mailto: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".
I wasn't showing it as a use case, I was showing it as illustrative of 
the syntax. I could have just done
acc( $o : MyClass();
         $f1 : fun1( $o ),
         $f2 : fun2( $o );
         somBooleanFunc( $f1, $f2 ) )

Mark
>
> 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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