Why no axes(::Tuple)?

New to Julia
1

Is there a good reason why axes (source) isn’t defined for tuples? My (perhaps naive) guess was they would be treated much the same as vectors.

(My reason for wondering is that this is what made me implement my own version of searchsortedlast that works for tuples in another question.)

1 Like
2

Tuples only have one dimension, so I don’t think axes make much sense. Is not eachindex good for what you are looking for?

2 Likes
3

It is. But some functions (such as mentioned searchsortedlast) depend on axes.

And by that logic axes(::AbstractVector) doesn’t make much sense either and yet it is that implementation that searchsortedlast rely on :slight_smile:

4

This seems like a bigger reason to change searchsortedlast than it does to add axes(::Tuple)

1 Like
5

FWIW here are the docstrings

axes(A)

  Return the tuple of valid indices for array A.

eachindex(A...)

  Create an iterable object for visiting each index of an AbstractArray A in an efficient manner

Both seem to be written keeping arrays in mind, and it’s not clear why one should be preferred for indexing Tuples over the other.

The correct function here seems to be keys:

julia> keys((1,2))
Base.OneTo(2)

which has the docstring

keys(iterator)

  For an iterator or collection that has keys and values (e.g. arrays and dictionaries), return an iterator over the keys.

This is more general than axes.

6

To me it seems that axes works for tuples.

julia> a = (1,2,3,4,'a')
(1, 2, 3, 4, 'a')

julia> typeof(a)
Tuple{Int64, Int64, Int64, Int64, Char}

julia> axes(a)
(Base.OneTo(5),)

julia> @which axes(a)
axes(t::Tuple) in Base at tuple.jl:28
3 Likes
7

Yeah, there’s been a functional axes(::Tuple) since Julia v1.1.

3 Likes
8

I must have done something wrong. Sorry for taking up everybody’s time. It works for me too. I felt sure that I had tested. But I guess that I must have only tested with a tuple in searchsortedlast, and that function isn’t defined for tuples. I guess that I should submit a pull request on sort.jl instead.

1 Like
9

Should this be documented? Currently the docstring for axes seems to suggest that it’s only for arrays

2 Likes