While working on a problem, I was using
EvenQ in a
RegionPlot. I came across this interesting case (simplified here for specificity). I expected to see a bunch of stripes, but got nothing:
However, it was fine if I used
Mod to the same effect instead:
I also get the correct results if I substitute
EvenQ. I also tried a version with
Assert[Head[#]==Integer]& included appropriately, and it did not ever raise an error, but the Mathematica evaluation model is still a bit mystical to me in some bits.