[thesz]

You missed the word "usually". You really, really do not need a print within the body of a loop of any tightness. But you can have it.

The foldl example of yours should be split into a property checking and controlling for expected properties of the input. The first part is done via quickcheck and second part usually is done with assertions and/or traces.

But nothing preclude you from having your trace there, inside foldl argument. This is clearly wrong place to have it, but still you can have it there.

So I repeat, you can have your traceEvents everywhere.