Thinking about zero-cost abstractions. Thinking about how I found a bit of C# code that did: array = new_item + array; ...and realising a few things: 1. Knowing this is bad is instinctive. Didn't even need to think about it. 2. The person who wrote this has no idea why this is worse than "array = array+ new_item" 3. Nothing in the language would guide them towards this knowledge. 4. This is probably rampant in all the other bits of code I don't see. 5. Zero-cost abstractions never are.