On Sun, Oct 16, 2016 at 5:32 PM, Ian Lance Taylor <i...@golang.org> wrote:

> On Sun, Oct 16, 2016 at 5:25 PM, Liam <networkimp...@gmail.com> wrote:
> >
> > On Sunday, October 16, 2016 at 5:13:36 PM UTC-7, Ian Lance Taylor wrote:
> >>
> >> On Sun, Oct 16, 2016 at 3:34 PM, Liam <networ...@gmail.com> wrote:
> >> >
> >> > On Sunday, October 16, 2016 at 2:56:42 PM UTC-7, Ian Lance Taylor
> wrote:
> >> >
> >> >> To argue that this should go into the standard library, look at some
> >> >> corpus of Go code and find out how often it occurs.  If it occurs
> >> >> fairly often, you've got a good case.
> >> >
> >> >
> >> > Fairly often; i.e. as often as Replace or Trim*? In my experience it
> >> > passes
> >> > that test.
> >>
> >> This is something that can actually be measured.
> >
> >
> > By doing grep 'append.*append' ? And '\[:.*len\(.*\).*\+[0-9]+.*\]' ?
> > Neither of these will be accurate.
> >
> > Part of my point is that Insert operations are semantically obscured.
> Understood.  But my guess is that insertion operations are fairly
> rare--much less common than Replace or Trim.  People obviously append
> to slices all the time, but I suspect that they tend to write their
> slice operations to not require inserting a single element in the
> middle of the slice, because insertion is by definition O(N) rather
> than O(1).  I could certainly be wrong, but that guess leads me to
> suspect that adding a function for something that can easily be
> written in a single expression is overkill.  Since I am only guessing,
> and since it seems to me that you are also guessing, I think we should
> measure rather than guess.

You characterize optimization as a widespread habit. Most code isn't
optimized, as it doesn't need to be. Most coders follow the first advice
found, which in my case was Insert() on [1]. If you wish the most optimal
solution to be widespread, stdlib would be a good vehicle :-)

I would attempt to provide data confirming my guess, but I can't see how to
do that without spending a lot of time hunting for semantically invisible
operations. Since there are two authoritative suggestions for this op, it's
a reasonable guess that it's widely done.

BTW, we are having this discussion because fmt does not support thousands
grouping, which also seems like a common need.

[1] https://blog.golang.org/slices

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