add signatures for reverse

[mcol]

In stan-dev/math#1650 I added the implementation of reverse. We should expose the following signatures:

vector reverse(vector)
row_vector reverse(row_vector)
int[] reverse(int[])
real[] reverse(real[])

[bob-carpenter]

Is the C++ code general enough to reverse an arbitrary T[] and not just int[] and real[]? If so, we can add a lot more signatures than the above.

[mcol]

Yes, it should be, but I don't know how to express it in signature form.

[bob-carpenter]

In the functions manual, it'll just be T[] reverse(T[] x) I don't know if stanc3 makes this easier, but in the old compiler, we just did a loop over base types and array dimensions and added all the signatures up to a fixed depth.

…

On Jan 30, 2020, at 3:55 PM, Marco Colombo ***@***.***> wrote: Yes, it should be, but I don't know how to express it in signature form. — You are receiving this because you commented. Reply to this email directly, view it on GitHub, or unsubscribe.

[rok-cesnovar]

Should be fairly easy to add this in stanc3. Will make a PR once the release stuff settles.

[wds15]

This is still active? I just missed this neat function when writing the COVID model. Not urgent at all... just bumping (but @rok-cesnovar is probably busy with lots of other stuff which I throw at him - sorry).

[rok-cesnovar]

Yes, still active but I dropped the ball on this and #452
They both take 15 minutes, but it simply slipped my mind. @mcol did a good job adding them in Math and I feel bad I forgot. Ping me next time I forget Marco :)

On my TODO now so will add after the feature freeze.