On Jul 12, 2020, at 1:43 PM, Axel Wagner <axel.wagner...@googlemail.com> wrote: > > > > On Sun, Jul 12, 2020 at 9:33 PM Bakul Shah <ba...@iitbombay.org> wrote: > On Jul 12, 2020, at 11:11 AM, Gert <gert.cuyk...@gmail.com> wrote: > > > > https://play.golang.org/p/6xMgjr1IyFD > > > > var fn myHandler > > fn = func(w http.ResponseWriter, r *http.Request) { > > fn.GET(w, r) > > } > > > > Just wondering if it's possible somehow to write this in one line like so > > > > var fn myHandler = func(w http.ResponseWriter, r *http.Request) { > > fn.GET(w, r) > > } > > The issue is that fn's type can't be completely determined until > the RHS func is fully analyzed but for that to work fn must be > known! > > Why? ISTM the type is mentioned twice - once as "myHandler" on the LHS and > once in the signature on the RHS. And there isn't even a way to write down a > function literal without mentioning the full type. On the surface, this seems > like a relatively straightforward scoping issue, introduced by the fact that > the scope of a variable declaration starts at the end of it's VarSpec, not > the "=". Interestingly though, the initialization rules prevent this from > working at the package-level, where this scoping problem doesn't exist: > https://play.golang.org/p/IPMxtYETGsg
You're right. > > Also note that the first definition won't do what you may be thinking > it does. The`fn.GET` call will be to the existing value of fn, not > the result of the assignment. > > No, it won't. The function-literal closes over `fn`, so it will use whatever > is assigned at call-time. > https://play.golang.org/p/VCvCt8J8Zcw > I use this pattern all the time to define a recursive function without > polluting the package-scope. Right again. What matters is the value of fn when the function is called, not when it is defined. Clearly I wasn't thinking clearly. Thanks for setting me straight. And apologies to Gert. -- 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/9D3EE282-2C7A-42DA-8282-CBFFF9C3935A%40iitbombay.org.
