One thing that's missed in the common conception of DRY is that the original formulation in The Pragmatic Programmer spoke in terms of pieces of knowledge. I w

One thing that's missed in the common conception of DRY is that the original formulation in The Pragmatic Programmer spoke in terms of pieces of knowledge. I won't speak to which is "really" DRY, but I think the original formulation is more useful. The more typical focus on surface syntax misses out in two respects. First, a single piece of knowledge might be represented in multiple places even when they look different. For instance, if I'm saying "there's a button here" in HTML and in JavaScript and in CSS, there won't be any syntactic repetition but that's not DRY per TPP. Second, just because there is syntactic repetition doesn't mean you're encoding the same piece of knowledge. Sometimes two pieces of code happen to be the same, but each looks that way for different reasons and are more likely to change independently than together. In that case, unifying them isn't DRY (per TPP). I joke that you're not improving that code, simply compressing it. I think that original formulation is pretty spot on, although even then would note an exception for deliberately saying important things in different ways for error detection and clarity, but only if they are actually checked against each other.