Re: [rules-dev] accumulate to acc

On 19/08/2011 10:32, Ansgar Konermann wrote: The behaviour is the same, it's just more compact and provides a clause for a guard, I also want to explore function chaining, like with functional programming. I felt we made some mistakes on the accumulate syntax and this is an opportunity to try and get it right, without breaking backwards compability. The comma separation in the syntax makes it very hard to evolve, hence the; in the new 'acc' for the segments. further 'accumulate' is quite verbose. I also considered using 'for' instead of 'acc', as in essence it is a for loop over a stream of data, as I thought maybe developers might find that more familiar. acc( $o : Order() from list; $min : min( $o.value ), $max : max( $o.value ); $min > 100 && $max < 200 ); The above will take a list of Orders and for each value execute the function(s) on it. That is the same as if it was an accumulate. We allow the function result to be bound, $min and $max are bound to the result. We then allow a guard on the result of the accumulate which will only allow those results to propagate if the guard is true. Example with 'for' instead: for( $o : Order() from list; $min : min( $o.value ), $max : max( $o.value ); $min > 100 && $max < 200 ); You could do this on the old accumulate as follows: $m : Map() from accumulate( $o : Order() from list, minMaxFunction( $o ) ) // user plugged in function that executes two functions and binds results to a map. $min : Number() from $m.min $max : Number() from $m.max eval( $min > 100 && $max < 200 ) This is virgin territory, and we need to be free to make mistakes and evolve the syntax, while trying to keep backwards compatability as long as possible. At some point we can deprecate older syntaxes and produce something much cleaner. Mark