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/e3bae2b0-6f0b-4302-b7e3-04103954d361n%40googlegroups.com.
