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stan-dev / stanc3

The Stan transpiler (from Stan to C++ and beyond).
BSD 3-Clause "New" or "Revised" License
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How should tuples be represented in get_dims()? #1242

Closed WardBrian closed 1 year ago

WardBrian commented 2 years ago

In the spirit of https://github.com/stan-dev/stanc3/issues/820, we need to decide how tuples should be represented by get_dims. The return value being type vector<vector<size_t> strongly implies rectangular objects, which tuples are not.

WardBrian commented 1 year ago

During today's language meeting @bob-carpenter suggested we may just be able to deprecate and remove this function. The CmdStan source only uses it twice, and it's largely redundant with get_param_names (especially if we go with #1245)

WardBrian commented 1 year ago

Another possibility besides deleting it is doing the same thing var_context has to do and building it up such that each tuple sub-part has a dimension, e.g. array[2] tuple(real, array[3] int) x would result in a length-2 get_dims, { { 2 }, { 2, 3 } }.

This would probably only make sense if we changed get_param_names to have the same behavior and return { "x.1", "x.2" } for the above (currently it would return just { "x" })

WardBrian commented 1 year ago

Looking at where get_param_names and get_dims are typically used, it seems like they are almost always used in conjunction with a var_context, so doing what they do (described in the previous comment) seems correct.

WardBrian commented 1 year ago

With the addition of unconstrain_array in #1305, we should probably deprecate the get_dims function, especially since ragged arrays etc don't even have the hacky workaround from above.