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logicchains • yesterday at 5:56 PM • 4 replies • view on HN

Your handwritten one has a major performance bug:

    found := false
    for _, v := range s {
        if v == needle {
            found = true
            break
        }
    }
Do you see it? It copies the v into a local variable, which could be tremendously wasteful if it's a large struct. You should instead be taking a pointer to s[i] and comparing the value there with `needle`.

If you'd used `slices.Contains(s, needle)`, on the other hand, it could have such a performance bug in it and you'd never know.

Replies

kajman • yesterday at 7:23 PM

> If you'd used `slices.Contains(s, needle)`, on the other hand, it could have such a performance bug in it and you'd never know.

Perhaps you're much better at programming than I am, but I prefer these semantics in a language because I figure they're much more likely to have been optimized empirically, support vectorization, and be less buggy than another rote loop I'm trying to speed through.

irq-1 • yesterday at 8:59 PM

You're right. Just for information, slices.Contains() uses the index, not a copied value.

https://cs.opensource.google/go/go/+/refs/tags/go1.26.5:src/...

boredatoms • yesterday at 7:37 PM

or contains() could be written by those who can write performant code, ..once

mathisfun123 • yesterday at 7:19 PM

> on the other hand, it could have such a performance bug in it and you'd never know.

wut...? the debate isn't between closed (incompetent) source and open (competent) source - the debate is between verbose language and expressive language.