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John Carmack on mutable variables

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498 points azhenley | 1 comments | 31 Oct 25 02:34 UTC | HN request time: 0.271s | source
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nixpulvis ◴[31 Oct 25 13:49 UTC] No.45771961[source]▶
I try to keep deeper mutation to where it belongs, but I'll admit to shadowing variables pretty often.

If I have a `result` and I need to post-process it. I'm generally much happier doing `result = result.process()` rather than having something like `preresult`. Works nicely in cases where you end up moving it into a condition, or commenting it out to test an assumption while developing. If there's an obvious name for the intermediate result, I'll give it that, but I'm not over here naming things `result_without_processing`. You can read the code.

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1. swid ◴[31 Oct 25 21:29 UTC] No.45776914[source]▶
I'm going to ignore the actual names used here - you can use any name you want. I think this pattern is vulnerable to introducing bugs that allow security bugs. I'm imagining process being some kind of sanitization or validation. Then, you have this thing called result, and some of the time it might be "safe" or processed, and sometimes not. Sometimes people will process it more or less than once with real consequences.

So yeah, definitely it is much better to name the first one in a way that makes it more clear it hasn't been processed yet.