add allcombinations

[bkamins]

add allcombinations function. see JuliaData/DataFrames.jl#3031 for an example implementation.

[codecov]

Codecov Report

Merging #47 (35723d7) into main (3e905a6) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main      #47   +/-   ##
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  Coverage   95.12%   95.12%           
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  Files           1        1           
  Lines          41       41           
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  Hits           39       39           
  Misses          2        2           

Impacted Files	Coverage Δ
src/DataAPI.jl	95.12% <ø> (ø)

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[bkamins]

@nalimilan - now I realized that the approach proposed here (and discussed on slack) cannot be used.
The reason is that we cannot dispatch on DataFrame since its type is DataType (it is not a function).

Maybe we should leave JuliaData/DataFrames.jl#3031 as it is then? Or do you see any other solution? The only I can see is that allcombinations would define a table-like type that then would be passed to DataFrame constructor. But then we would need to provide implementation of the logic of the function in DataAPI.jl, which I think we should not do.

[nalimilan]

Can't we just define methods like allcombinations(::Type{DataFrame}, ...)?

[bkamins]

Ah - right. We can 😄. In this case can you please review this PR?

[nalimilan]

@quinnj We could mention in the docstring that TableOperations owns allcombinations(NamedTuple, ...) and implement a method there.

[bkamins]

@quinnj - could you have a look at this PR before I merge it and make a release (and finish JuliaData/DataFrames.jl#3031 a follow-up PR in DataFrames.jl)? Thank you!

[bkamins]

Thank you!