The 'diff' package you showed identifies the changed object index by means of a "Path" attribute in the Changelog entry. If the top level object is a slice, then Atoi(change.Path[0]) is the index into the slice.
On Friday, 14 July 2023 at 10:47:47 UTC+1 Mark wrote: > Hi Brian, > Your code certainly identifies the different items. > However, that's not a diff tool in the sense I mean. > Unix diff and tools like it don't just say x[i] != y[i], they find the > longest common subsequences and in essence produce a series of edit > commands that would turn slice x into slice y. > There are quite a few go diff tools that will do this, including my own > <https://pkg.go.dev/github.com/mark-summerfield/go-diff> based on > Python's difflib sequence matcher. > What I want to do is find one that does this for slices of structs where > only one struct field is considered for comparison purposes. > > On Friday, July 14, 2023 at 10:00:34 AM UTC+1 Brian Candler wrote: > >> I forgot you wanted generics: >> https://go.dev/play/p/PhGVjsWWTdB >> >> On Friday, 14 July 2023 at 09:47:21 UTC+1 Brian Candler wrote: >> >>> You seem to be saying "if the S field is different then I want to >>> consider these two structs different, and get pointers to the two structs. >>> If the S field is the same then I want to skip the pair entirely". Is that >>> right? >>> >>> The required semantics are not entirely clear, but it sounds like a >>> handful of lines of code to implement - there's no point importing and >>> learning a third party library. >>> >>> On the assumption that all the elements to be compared are in >>> corresponding positions in a and b: >>> https://go.dev/play/p/Y71sLUpftzR >>> >>> On Friday, 14 July 2023 at 09:11:35 UTC+1 Mark wrote: >>> >>>> In fact the diff pkg mentioned above does work but is of no use to me >>>> since for each change it gives back only the field(s) used, not the >>>> original structs (or pointers to them), so I can't see any way back to the >>>> original structs (or their slice indexes). >>>> >>>> On Friday, July 14, 2023 at 8:58:41 AM UTC+1 Mark wrote: >>>> >>>>> What I really want to do is to be able to diff slices of structs on >>>>> the basis of one single field. >>>>> For example, given: >>>>> ``` >>>>> type Item struct { >>>>> I int >>>>> S string >>>>> } >>>>> ``` >>>>> and given `a` and `b` are both of type`[]Item`, I want to diff these >>>>> slices based purely on the `S` field, ignoring the `I` field. >>>>> >>>>> This diff pkg <https://pkg.go.dev/github.com/r3labs/diff/v3> claims >>>>> to be able to do this (something I'm testing, so I don't know either way >>>>> yet), but in any case, it is incredibly slow. >>>>> >>>>> On Friday, July 14, 2023 at 8:31:39 AM UTC+1 Peter Galbavy wrote: >>>>> >>>>>> As a slight digression - I thought I was going mad, but 'slices' and >>>>>> 'maps' are new :-) Only in 1.21 though... >>>>>> >>>>>> Well, there is a lot of boiler plate that maps.Keys() will get rid of. >>>>>> >>>>>> On Thursday, 13 July 2023 at 10:06:01 UTC+1 Brian Candler wrote: >>>>>> >>>>>>> Structs are already comparable, but all fields must be the same: >>>>>>> https://go.dev/play/p/XwhSz4DEDwL >>>>>>> >>>>>>> I think your solution with function 'eq' is fine. You can see the >>>>>>> same thing in the standard library in slices.CompactFunc and >>>>>>> slices.EqualFunc >>>>>>> https://pkg.go.dev/slices#CompactFunc >>>>>>> https://pkg.go.dev/slices#EqualFunc >>>>>>> >>>>>>> For the case of "ordered" rather than "comparable", have a look at >>>>>>> slices.BinarySearchFunc and related functions. >>>>>>> >>>>>>> On Thursday, 13 July 2023 at 09:29:38 UTC+1 Mark wrote: >>>>>>> >>>>>>>> I have a package which has a function `Do[T comparable](a, b []T) >>>>>>>> Result`. >>>>>>>> I have a struct: >>>>>>>> ```go >>>>>>>> type N struct { >>>>>>>> x int >>>>>>>> y int >>>>>>>> t string >>>>>>>> } >>>>>>>> ``` >>>>>>>> Is it possible to make `N` comparable; in particular by a field of >>>>>>>> my choice, e.g., `t`? >>>>>>>> >>>>>>>> Or will I have to make, say, `DoFunc(a, b []N, eq func(i, j N) >>>>>>>> bool) Result` with, say, >>>>>>>> `func eq(i, j N) { return i.t == j.t }`? >>>>>>>> >>>>>>> -- 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. To view this discussion on the web visit https://groups.google.com/d/msgid/golang-nuts/5cc6237b-1dcc-49f8-b426-69edf2405484n%40googlegroups.com.
