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Updated LoopvarExperiment (markdown)

David Chase 2023-06-05 14:03:55 -04:00
parent 75f0dd04aa
commit 51a037acb5
1 changed files with 2 additions and 2 deletions
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4
LoopvarExperiment.md

@ -116,7 +116,7 @@ For full details, see [the design document](https://go.googlesource.com/proposal
## Can this change break programs? ## Can this change break programs?
Yes, it is possible to write programs that this change would break. For example, here is a surprising way to add the values in a list using a single-element map: Yes, it is possible to write programs that this change would break. For example, here is a surprising way to add the values in a list using a single-element map:
```
func sum(list []int) int { func sum(list []int) int {
m := make(map[*int]int) m := make(map[*int]int)
for _, x := range list { for _, x := range list {
@ -127,7 +127,7 @@ func sum(list []int) int {
} }
return 0 return 0
} }
```
It depends on the fact that there is only one `x` in the loop, so that `&x` is the same in each iteration. With `GOEXPERIMENT=loopvar`, `x` escapes the iteration, so `&x` is different on each iteration, and the map now has multiple entries instead of a single entry. It depends on the fact that there is only one `x` in the loop, so that `&x` is the same in each iteration. With `GOEXPERIMENT=loopvar`, `x` escapes the iteration, so `&x` is different on each iteration, and the map now has multiple entries instead of a single entry.
And here is a surprising way to print the values 0 through 9: And here is a surprising way to print the values 0 through 9: