> Are you sure that's the only edge-case? Because this thread is kinda long 
> and there might even be things we are not thinking about. 

In the original discussion above I see one opinion toward comparing headers 
and four toward by element values (like strings). I didn't see any 
additional edge cases listed.

The usecase you mentioned above seems - to me - to be served by a 
> map[string]*T just fine. Did I misunderstand it?

Each path represented as a slice of coordinates could be easily encoded to 
a string and compared that way.

As far as resource expenses go, we'd need benchmarks to say much. I 
understand looking at expensive cases too, but that doesn't mean that there 
aren't smaller regular use cases. Goroutines can be overused too.


On Wednesday, January 31, 2018 at 10:24:30 AM UTC-6, rog wrote:
> On 30 January 2018 at 23:19,  <matthe...@gmail.com <javascript:>> wrote: 
> >> - When slices can be compared, they can be used as map keys. What 
> happens 
> >> if the contents of a slice are changed after it has been added to a 
> map? 
> > 
> > 
> > I’m not too familiar with Go map internals, but my thought is the key 
> hash 
> > would depend on the backing array values. Go maps also allow reading the 
> > keys back using iteration so the slice backing array (up to length) 
> would 
> > have to be copied. If the slice contents are changed then that would be 
> a 
> > different key and the original key would be intact. 
> Note that copying the slice contents to make a map key implies 
> that using a slice as a map key might imply copying a whole tree, 
> which seems rather expensive to me (especially as it might end up 
> using more memory than the original if some elements are duplicated, 
> unless an alias-aware copy algorithm is used which would be 
> more expensive still) 
> BTW you can already do something like this: 
> https://play.golang.org/p/q4bz8-AckN3 
> You can even do it without reflect, which I'll leave as an exercise 
> for the reader :) 

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