.== not defined for tuples

[jiahao]

Having .== work on tuples would simplify a lot of dimensions checking in the linear algebra routines.

julia> A=randn(10,10);

julia> any(size(A).==10)
ERROR: no method .==((Int64,Int64),Int64)

julia> all([size(A)...].==10)
true

[StefanKarpinski]

That seems like a reasonable feature to me.

[mlubin]

Wouldn't checking the dimension like that have a hidden memory allocation for the temporary boolean array?

[jiahao]

for the [size(A)…] code, yes. However,
(a) .== on tuples doesn’t have to be implemented via a temporary array, and
(b) when used to check array dimensions, this is hardly a time- or memory-critical application.

[JeffBezanson]

We are pretty close to being able to do any(size(A).==size(B)) without any intermediate tuples.

The painful case here is tuple .== array. Do we iterate over both, or compare the array to each element of the tuple, or the other way?

[IainNZ]

@jiahao is this still a desired feature?

[jiahao]

yes

[mbauman]

Implemented by #17623, which has also answered how to handle tuple .== array. It's also super-efficient when using same-length tuples, but comparisons against scalars could probably be optimized further if you want to use this for linear algebra dimension checks.