Hi Brian, Ah, thank you, that helped a lot. On Friday, July 14, 2023 at 11:54:51 AM UTC+1 Brian Candler wrote:
> 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/eb4db5e8-598f-4ce9-bc6d-38f9c5ed6861n%40googlegroups.com.
