You can use len to determine the sizeof a struct.
https://play.golang.org/p/f0x8p_04lP1 ;)
On Sun, 2021-10-24 at 16:44 -0700, jlfo...@berkeley.edu wrote:
> Thanks for the replies.
>
> I had been trying to translate the trick from C into Go where you can
> find how many structures are in an initialized array of structures
> by dividing the size of the array by the size of one structure. As
> I've learned, not only isn't this possible, because you can't get
> the size of one structure, but also because it isn't necessary.
> Instead, using a slice of structures rather than an array, I can just
> do "len(structslice)".
> That gives me what I need.
>
> But, I still have some questions about the responses. First, I think
> the expected value of len(struct) should be its size, in bytes,
> like with a string. Are there any examples of problems this would
> cause? I don't understand why this has to be
> unsafe. (It could even be done at compile time). I also don't
> understand the comment about recursive calls. Since it's possible
> to assign one structure to another I would think that the structure
> length is known. Since I'm new to Go I'm probably
> not aware of the finer points that would make this not so.
>
> Cordially,
> Jon Forrest
>
> On Sunday, October 24, 2021 at 11:29:58 AM UTC-7
> filipdimi...@gmail.com wrote:
> > len() works on indexed types - arrays, slices, maps, strings. It
> > also works on buffered channels but we can consider that a
> > sequence. I don't consider a struct a sequence. It's non-obvious
> > what the behaviour would be. Both of these sound reasonable: len()
> > should be the memory size of the struct like sizeof in C/C++ *or*
> > it should be the sum of the lengths of its (sequence) members.
> >
> > The first case is way too low-level for Go, because it belongs to
> > an unsafe operation so that's an easy no, ... and it already exists
> > as unsafe.Sizeof().
> >
> > The second case (len being the sum of its members' lengths) would
> > require recursive calls, and almost surely infinite cycles as we
> > eventually get to pointers.
> >
> > On Sunday, October 24, 2021 at 8:11:37 PM UTC+2
> > jlfo...@berkeley.edu wrote:
> > > I noticed that the len() function doesn't take a struct as an
> > > argument (see below).
> > > This is a big surprise. Can someone shed some light on why this
> > > restriction exists?
> > >
> > > Cordially,
> > > Jon Forrest
> > >
> > > ----------
> > > package main
> > >
> > > import "fmt"
> > >
> > > var s struct {
> > > i1 int
> > > i2 int
> > > }
> > >
> > > func main() {
> > > fmt.Printf("len(s) = %d\n", len(s)) // -- invalid argument
> > > s (type struct { i1 int; i2 int }) for len
> > > }
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