13.29. Functions of the Conditional Element Accumulate

  • average
  • min
  • max
  • count
  • sum
  • collectList
  • collectSet
These common functions accept any expression as input. For instance, if someone wants to calculate the average profit on all items of an order, a rule could be written using the average function: 
rule "Average profit"
when
    $order : Order()
    accumulate( OrderItem( order == $order, $cost : cost, $price : price );
                $avgProfit : average( 1 - $cost / $price ) )
then
    // average profit for $order is $avgProfit
end
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