Is there any convenient way to create alias of indexes and data in Array2？

[qindazhu]

As we will declare many classes (Fsa, AuxLabels, Cfsa, etc.) with Array2, wondering if there is any convenient way to create alias of indexes and data so that we can use those alias in functions to make code clear (otherwise we may create those alias in functions again and again)

For example (pseudo code)

using Fsa = Array2<Arc*, int32_t>
alias Fsa::arc_indexes = Fsa::indexes;
alias Fsa::arcs = Fsa::data;

One possible approach I thought of is wrapping Array2 in a struct:

struct Fsa {
 Array2<Arc *, int32_t> m;
 Arc *&arcs = m.data;
 int32_t *&arc_indexes = m.indexes;
}；

(Two extra advantages of using struct here are that:

1. Users cannot misuse class as another class that has the same template parameters in Array2, for example they can not pass Fsa to a function that accepts Cfsa where Fsa = Cfsa = Array2<Arc*, int32_t>)
2. We can define extra methods in those structs, such as NumStates(), FinalStates(), NumArcs. Otherwise it seems we could just define those methods in Python code (and cannot do this in C++ code)?
   )

[danpovey]

We resolved this via in-person discussion. Will use the generic Array2 names like indexes and data, rather than Fsa-specific notation.

…

On Tue, Jun 9, 2020 at 4:43 PM Haowen Qiu ***@***.***> wrote: As we will declare many classes (Fsa, AuxLabels, Cfsa, etc.) with Array2, wondering if there is any convenient way to create alias of indexes and data so that we can use those alias in functions to make code clear (otherwise we may create those alias in functions again and again) For example (pseudo code) using Fsa = Array2<Arc*, int32_t> alias Fsa::arc_indexes = Fsa::indexes; alias Fsa::arcs = Fsa::data; One possible approach I thought of is wrapping Array2 in a struct: struct Fsa { Array2<Arc *, int32_t> m; Arc *&arcs = m.data; int32_t *&arc_indexes = m.indexes; }； (An extra advantage of using struct here is that users cannot misuse class as another class that has the same template parameters in Array2, for example they can not pass Fsa to a function that accepts Cfsa, where using Fsa = Array2<Arc*, int32_t>, using Cfsa = Array2<Arc*, int32_t>) — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub <https://github.com/danpovey/k2/issues/56>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAZFLO5VV7QYRHL76W56HETRVXY3NANCNFSM4NZF3MIA> .

[qindazhu]

Sure, and will add IndexT size2 in Array2 as the total number of elements in data (from indexes[0] to indexes[size])