Display NTuples with more than one element as NTuples rather than Tuples?

Internals & Design
1

This example is somewhat specific to making displayed types more legible, although this might help more generally.
Currently, we have

julia> Tuple{Int, Int, Int}
Tuple{Int64, Int64, Int64}

julia> Tuple{Int, Int, Int, Int}
NTuple{4, Int64}

I feel the latter form is much more readable, and would prefer this display for 2 or 3-element NTuples as well. This becomes especially important if the individual elements are long:

julia> using BlockArrays, ArrayLayouts

julia> T = BlockedUnitRange{ArrayLayouts.RangeCumsum{Int64, StepRange{Int64, Int64}}};

julia> Tuple{T, T, T}
Tuple{BlockedUnitRange{RangeCumsum{Int64, StepRange{Int64, Int64}}}, BlockedUnitRange{RangeCumsum{Int64, StepRange{Int64, Int64}}}, BlockedUnitRange{RangeCumsum{Int64, StepRange{Int64, Int64}}}}

julia> Tuple{T, T, T, T}
NTuple{4, BlockedUnitRange{RangeCumsum{Int64, StepRange{Int64, Int64}}}}

The latter is certainly more concise and easier to parse than the former.

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2

PR created:

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3

Would this constitute a breaking change? I should hope that nobody is using string(typeof(some_tuple))) in Julia code but it might matter to some shell script.

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4

There have been quite a few changes to displayed forms in minor releases, e.g. named tuples in a recent release, and the Array{T,1} to Vector{T} change sometime bank. This isn’t seen as breaking.

5

This is really a taste/preference thing. Personally, I like the current print-up-to-three behavior; I often find three is used as a cutoff before eliding in many contexts.

If you just have a handful of commonly-used long types like that, you could export them from your package and then printing will use those shorthands:

julia> import BlockArrays, ArrayLayouts

julia> @eval BlockArrays begin
       const StepAxis = BlockedUnitRange{ArrayLayouts.RangeCumsum{Int64, StepRange{Int64, Int64}}}
       export StepAxis
       end

julia> T = BlockArrays.BlockedUnitRange{ArrayLayouts.RangeCumsum{Int64, StepRange{Int64, Int64}}}
StepAxis (alias for BlockArrays.BlockedUnitRange{ArrayLayouts.RangeCumsum{Int64, StepRange{Int64, Int64}}})

julia> Tuple{T,T,T}
Tuple{BlockArrays.StepAxis, BlockArrays.StepAxis, BlockArrays.StepAxis}
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