# When is it safe to use Base.OneTo?

**URL:** <https://discourse.julialang.org/t/when-is-it-safe-to-use-base-oneto/12512>\
**Category:** Performance\
**Created:** [July 19, 2018, 8:45pm UTC](https://discourse.julialang.org/t/when-is-it-safe-to-use-base-oneto/12512 "2018-07-19T20:45:46Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![favba](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/favba/32/2735_2.png) [@favba](https://discourse.julialang.org/u/favba)\
**Post date:** [July 19, 2018, 8:45pm UTC](https://discourse.julialang.org/t/when-is-it-safe-to-use-base-oneto/12512/1 "2018-07-19T20:45:46Z")

</div>

Since `Base.OneTo` is not exported I am suspicious that there might be some gotchas with it.

I implemented a [padded array](https://github.com/JuliaMath/FFTW.jl/pull/54) interface to perform in-place r2c and c2r fft transformations.  
For that I have to create views that are always something like (pseudo-code) `@view a[begin:(end-2), : , : , ... , :]` where `begin` is the first index of the first dimension.  
As you can see below, using `OneTo`s gives me the best performance.  
I’ll be creating views of plain julia’s `Array`s, so no array with custom indices. So, is it safe to use `Base.OneTo` directly?

```julia-repl

julia> data = rand(130,128,128);

julia> a = view(data,1:128,1:128,1:128);

julia> b = view(data,1:128,:,:);

julia> c = view(data,Base.OneTo(128),Base.OneTo(128),Base.OneTo(128));

julia> using BenchmarkTools

julia> @btime sum($a)
  5.230 ms (0 allocations: 0 bytes)
1.0485345086366412e6

julia> @btime sum($b)
  4.549 ms (0 allocations: 0 bytes)
1.0485345086366412e6

julia> @btime sum($c)
  4.300 ms (0 allocations: 0 bytes)
1.0485345086366412e6

julia> versioninfo()
Julia Version 0.7.0-beta2.0
Commit b145832402* (2018-07-13 19:54 UTC)
Platform Info:
  OS: macOS (x86_64-apple-darwin17.6.0)
  CPU: Intel(R) Core(TM) i5-5287U CPU @ 2.90GHz
  WORD_SIZE: 64
  LIBM: libopenlibm
  LLVM: libLLVM-6.0.0 (ORCJIT, broadwell)
Environment:
  JULIA_NUM_THREADS = 2

```

Note that the `:` creates ranges of type ` Slice{OneTo{Int}}`, so it is taking the advantages of `OneTo`…