I am trying to implement a rule in Drools language. I need to add up two integer values from two variables. I have tried some different ways but none of them seem to work. I get either failure due to the "+" symbol or due to the "eval" function. I need to do the summation and then compare its value to another one for the rule to fire. These are the combinations I have already tried

```
     $generationGrain : ($smallerGenerationIndex.intValue() + App.GENERATION_TIME.intValue() ) 

     $generationGrain : $smallerGenerationIndex.intValue() + App.GENERATION_TIME.intValue()

     $generationGrain : eval($smallerGenerationIndex.intValue() + App.GENERATION_TIME.intValue())

     $generationGrain : eval($smallerGenerationIndex + App.GENERATION_TIME)

     $generationGrain : ($smallerGenerationIndex + App.GENERATION_TIME )  

     $generationGrain : ($smallerGenerationIndex.intValue() + App.GENERATION_TIME.intValue() ) 

```

Is it just not possible to do it or am I missing something? Should I just create an rule with the summation after the `then` and then another rule with the conditional and the other value?