>code is written once but read multiple times I'm familiar with the expression but it's not really written once, it's written and iterated upon. If I change so

>code is written once but read multiple times I'm familiar with the expression but it's not really written once, it's written and iterated upon. If I change something in a function that's called twice, I can be confident it will be the same change both places it's called: there's no programmatic way of verifying the change is the same if I copy and pasted, there I have to compare text. Humans aren't good at that. So in Carmack's example, what if someone adds side effects to the pure, inlined code which don't break anything at the time? They could cause issues when someone later assumes the inlined code is pure. Whereas, if you have pure function calls, this is all done for you by a machine designed for it.