According to code design mostly. It's not a syntax issue (both are fine syntax) but a logic issue. You should be able to trust that as long as your dimensions a

According to code design mostly. It's not a syntax issue (both are fine syntax) but a logic issue. You should be able to trust that as long as your dimensions are valid, any for loop over the resulting list works. And in graphics contexts, zero is typically a perfectly valid value to set one (or both) dimensions to (negative values, however, are not). Of course, you _can_ say "I think 0 is an invalid dimension" but given that plenty of frameworks and applications consider 0 just fine, that's kind of an unnecessary restriction for the sake of writing a conditional that is arguably irrelevantly "easier" to read.