R programming = adding random variable

I'm pretty new to R programming and having a minor problem. Here is the first part of the question which I was able to figure out:

1. Consider the experiment of rolling a pair of dice. Using R, show how would you define a random variable for the absolute value of the difference of the two rolls, using a user-defined function.

I'm stuck with part 2 which is:

Using R, add another random variable to the above probability space using a user defined function. The random variable is TRUE if the sum of the two rolls is even, and FALSE otherwise.

 I don't understand how to show how the random variable is TRUE if the sum of the two rolls is even

  Would really appreciate some help, thanks!

What I have tried:

S <- rolldie(2, makespace = TRUE)
  S <- addrv(S, U = X1 + X2)
  S <- addrv(S, FUN = is.even,
          invars = c("X1", "X2"), name = "V")