On Monday, 12 April 2021 at 17:01:38 UTC+1 theluk...@gmail.com wrote:
> I've heard several times from members of the community (on Matrix and
> possibly on answers) that a simple iteration like
>
> const mixed = "\b5Ὂg̀9! ℃ᾭG"
> for _, c := range mixed {
> ... do something with c (but not write to it)
>
> will actually silently allocate a slice of runes and decode the string
> into it, before iteration. I've heard it is done to prevent problems that
> occur when a programmer might overwrite data being iterated, which should
> be a no-brainer for programmers in general, but sure, whatever. So is it
> true in the case for constants? Is it true always, or only when writes
> occur to the source string or `c` in that case?
>
Writing to c won't make any difference (because it's a completely separate
variable, an int32 which doesn't share any memory with the original
string); and writing to the source string is impossible (because strings
are immutable in go).
Could it be possible that you're thinking of the opposite case? Given an
input slice b []byte, if you choose to iterate over it as a series of UTF-8
codepoints using
for _, c := range string(b) {
...
}
then I would expect the string(b) conversion to make a byte-for-byte copy
of b, because a string is immutable but b isn't.
https://play.golang.org/p/3TN2TwdEhk7
This isn't the same as exploding the string into a slice of int32 runes
up-front, but it might explain where the rumour came from.
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