As itinerary and the reslicing operation use the same backing array, you could just offset your indexes: https://play.golang.org/p/2ZzKST5J1g
I'm not sure if it's a good idea, could the sort.Slice implementation change in the future and make a regression? Le mercredi 8 mars 2017 18:22:48 UTC+1, Ain a écrit : > > > 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 >>>>> >>>> -- >>>> You received this message because you are subscribed to the Google >>>> Groups "golang-nuts" group. >>>> To unsubscribe from this group and stop receiving emails from it, send >>>> an email to golang-nuts...@googlegroups.com. >>>> For more options, visit https://groups.google.com/d/optout. >>>> >>> >>> -- You received this message because you are subscribed to the Google Groups "golang-nuts" group. To unsubscribe from this group and stop receiving emails from it, send an email to golang-nuts+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
