On Sun, Mar 14, 2021 at 2:59 PM 'Dan Kortschak' via golang-nuts
<golang-nuts@googlegroups.com> wrote:
>
> Now that a proposal for an approach to generics has been approved[1],
> it seems like a good time to again[2] raise the issue of how to be able
> to write code that has correlated types where types are structured but
> built-in, and so fields are not available to examine. The only case of
> this in the language is the relationship between float and their
> corresponding complex types. So for example in the case of wanting to
> write a simple generic Eigen Decomposition functions we would have
>
> type Real interface {
> type float32, float64
> }
>
> func Eigen[T Real](m, n int, data []T) (left, values, right []?, ok bool) {
> ...
>
> but, there is currently no way to specify that []? is a slice of
> complex(T, T).
>
> Having a syntax for this is obvious; being able to write []complex(T,
> T) in this place is entirely consistent with doing the same thing with
> structs where the types of struct fields are visible to the language
> user. Indeed, in the current generics proposal, the Gonum quaternion,
> dual, hyperdual and dual quaternion number types are easier to
> integrate into a generics system than the built in complex number types
> because they are based on structs.
>
> Similarly, general utility functions that would be useful in DSP to
> interconvert between complex and real would be
>
> func AsComplex[T Real](v T) ? /* a complex(T, T) */ { ...
>
> type Complex interface {
> type complex64, complex128
> }
>
> func Abs[T Complex](v T) ? /* a float of the correct size */ { ...
>
> Where in the latter being able to write real(T) to specify the type of
> the return value.
>
> Dan
>
> [1]https://blog.golang.org/generics-proposal
> [2]https://groups.google.com/g/golang-nuts/c/dZIdMJTO5ws/m/nQbBk7NrBgAJ
For the record Dan followed up on this at https://golang.org/issue/45049.
Ian
--
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/CAOyqgcV_8ucEkHmWVs-oS9j8jb-%3DqO4zWAJYx1qZrwnxkDSC0w%40mail.gmail.com.
