Another, OO-ish fix is to use method on custom type
(https://play.golang.org/p/a5S5rNog5h):
type itinerary []string
func (t itinerary) sort() {
sort.Slice(t, func(i, j int) bool {
return t[i] < t[j]
})
}
func main() {
itinerary := itinerary{"Philadelphia", "Chicago", "Boston", "Austin"}
itinerary[1:].sort()
fmt.Println("My new itinerary is", itinerary)
}
ain
On Wednesday, March 8, 2017 at 5:01:08 PM UTC+2, Val wrote:
>
> Sorry for not elaborating in the first place (I was trying to make the
> point very concise).
>
> This is the starting city : Philadelphia
>
> This are the other cities : Chicago, Boston, Austin
>
> The itinerary is the concatenation of starting city + other cities to be
> visited : [Philadelphia, Chicago, Boston, Austin]
>
> In this contrived example the first city is fixed, because this is where I
> am now, wherever I decide to go next. That's why I decide to reorder all
> cities of my itinerary except the first one.
>
> This is what my naive code what trying to achieve (expected value of slice
> itinerary after partial sort) : [Philadelphia Austin Boston Chicago]
>
> This is what the code actually produces (value of slice itinerary after
> partial sort) : [Philadelphia Boston Chicago Austin] , which is why i say
> it is broken : the last 3 items don't end up in alphabetical order like I
> expected them to be.
>
> In a real program, there would be various legit reasons to sort only part
> of a slice, and the items would not always have a builtin type like string,
> rather custom struct types.
>
> @CBanning Thanks, I had not thought of StringSlice! But it's not
> applicable in my real programs, which deal with custom struct types (not
> strings).
>
> @David Sorting the whole slice is not what I was trying to achieve,
> because I can't change my starting point.
>
> The bug in my code is that the two arguments I pass to sort.Slice are
> inconsistent : the portion to be sorted is a reslicing from itinerary,
> while the "less" closure indexes items of the whole itinerary.
>
> I brought up the "go vet" idea because I feel that whenever someone will
> do some reslicing directly in the first argument,
> - either the result will be "broken" like mine,
> - or the code in the less function will have to refer to the same
> (unnamed) resliced portion, which is imo convoluted : fix 1
> <https://play.golang.org/p/v0V8BQuJ_m> or fix 2
> <https://play.golang.org/p/z_52IQAhY4> .
>
> The most readable alternative I can think of while still using sort.Slice
> is to reslice in a new variable prior to sorting : fix 3
> <https://play.golang.org/p/ZgHyGOLiQO> .
>
> Best regards
> Val
>
> On Wednesday, March 8, 2017 at 3:25:48 PM UTC+1, David Peacock wrote:
>>
>> On Wed, Mar 8, 2017 at 8:32 AM, Valentin Deleplace <dele...@gmail.com>
>> wrote:
>>
>>> I did explain the expected result : "and I want to visit other cities
>>> in alphabetical order"
>>>
>>
>> Jan is correct; the characterization of a problem hinges on accurately
>> describing what you expect and what happened instead. Terms such as
>> "broken" and "does not work" are best avoided because others don't know
>> what your definitions are for these in the given context. :-)
>>
>> That being said, your alphabetical order is returned as you intend if you
>> adjust line 17 thusly:
>>
>> sort.Slice(itinerary[:], func(i, j int) bool {
>>
>> Cheers,
>> David
>>
>>
>>>
>>> Le 8 mars 2017 2:16 PM, "Jan Mercl" <0xj...@gmail.com> a écrit :
>>>
>>>> On Wed, Mar 8, 2017 at 2:10 PM Val <dele...@gmail.com> wrote:
>>>>
>>>> > What do you think?
>>>>
>>>> You should explain what you've expected to get instead of what you've
>>>> got. Without that, I for one, cannot figure out what you see as broken and
>>>> I have no idea why do you think it's not a good idea to sort a slice of a
>>>> slice. After all, it's just a slice as any other.
>>>>
>>>> --
>>>>
>>>> -j
>>>>
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>>
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