[Proposal] {Enum, Stream}.zip_all

[Greg Rychlewski]

Hi,

Would the community be interested in adding versions of of the Enum/Stream zip functions that allow for a default value to be set when the enumerables aren't all the same length?  I was thinking of the following name/arity combos:

{Enum, Stream}.zip_all/2 

{Enum, Stream}.zip_all/3 

{Enum, Stream}.zip_all_with/3

{Enum, Stream}.zip_all_with/4

Enum.zip_all_reduce/4

Enum.zip_all_reduce/5

I had some ideas for how to implement this and could work on a PR if the proposal is accepted.

Thanks

[Christopher Keele]

Not commenting on the feature itself, but I believe there's a convention in the collection stdlib of keeping the same function names, but accept an extra parameter, for default values. See:

• Enum.find/3
• Enum.find_value/3
• Map.pop/3
• Keyword.get/3

[Greg Rychlewski]

Thanks. I was thinking about that too, but for this particular feature I believe there would be an issue. Please let me know what you think: 

If we take Enum.zip as an example, it has a 1-arity version for accepting a list of enumerables and a 2-arity version accepting two single enumerables as arguments. If we wanted to allow for a default value in the zip/1 version it would conflict with the existing zip/2.