https://github.com/juliaarrays/identityranges.jl

Ranges that preserve indices of views
https://github.com/juliaarrays/identityranges.jl

Last synced: 22 days ago
JSON representation

Ranges that preserve indices of views

• Host: GitHub
• URL: https://github.com/juliaarrays/identityranges.jl
• Owner: JuliaArrays
• License: other
• Created: 2017-03-15T21:46:56.000Z (over 9 years ago)
• Default Branch: master
• Last Pushed: 2023-03-16T08:50:15.000Z (over 3 years ago)
• Last Synced: 2025-01-02T23:30:08.986Z (over 1 year ago)
• Language: Julia
• Size: 18.6 KB
• Stars: 2
• Watchers: 6
• Forks: 5
• Open Issues: 4
• Metadata Files:
  • Readme: README.md
  • License: LICENSE.md

Awesome Lists containing this project

README

          
# IdentityRanges

[![Build Status](https://travis-ci.org/JuliaArrays/IdentityRanges.jl.svg?branch=master)](https://travis-ci.org/JuliaArrays/IdentityRanges.jl)

[![codecov.io](http://codecov.io/github/JuliaArrays/IdentityRanges.jl/coverage.svg?branch=master)](http://codecov.io/github/JuliaArrays/IdentityRanges.jl?branch=master)

IdentityRanges are Julia-language a helper type for creating "views"

of arrays. They are a custom type of `AbstractUnitRange` that makes it

easy to preserve the indices of array views. The key property of an

`IdentityRange` `r` is that `r[i] == i` (hence the name of the

type/package), and that they support arbitrary start/stop indices

(i.e., not just starting at 1).

```julia

julia> A = reshape(1:24, 4, 6)

4×6 reshape(::UnitRange{Int64}, 4, 6) with eltype Int64:

 1  5   9  13  17  21

 2  6  10  14  18  22

 3  7  11  15  19  23

 4  8  12  16  20  24

julia> V = view(A, 2:3, 3:5)

2×3 view(reshape(::UnitRange{Int64}, 4, 6), 2:3, 3:5) with eltype Int64:

 10  14  18

 11  15  19

julia> axes(V)

(Base.OneTo(2),Base.OneTo(3))

julia> V[1,1]

10

julia> using IdentityRanges

julia> Vp = view(A, IdentityRange(2:3), IdentityRange(3:5))

view(reshape(::UnitRange{Int64}, 4, 6), IdentityRange(2:3), IdentityRange(3:5)) with eltype Int64 with indices 2:3×3:5:

 10  14  18

 11  15  19

julia> axes(Vp)

(2:3,3:5)

julia> Vp[1,1]

ERROR: BoundsError: attempt to access view(reshape(::UnitRange{Int64}, 4, 6), IdentityRange(2:3), IdentityRange(3:5)) with eltype Int64 with indices 2:3×3:5 at index [1, 1]

Stacktrace:

 [1] throw_boundserror(::SubArray{Int64,2,Base.ReshapedArray{Int64,2,UnitRange{Int64},Tuple{}},Tuple{IdentityRange{Int64},IdentityRange{Int64}},false}, ::Tuple{Int64,Int64}) at ./abstractarray.jl:484

 [2] checkbounds at ./abstractarray.jl:449 [inlined]

 [3] getindex(::SubArray{Int64,2,Base.ReshapedArray{Int64,2,UnitRange{Int64},Tuple{}},Tuple{IdentityRange{Int64},IdentityRange{Int64}},false}, ::Int64, ::Int64) at ./subarray.jl:206

 [4] top-level scope at none:0

julia> Vp[2,3]

10

julia> A[2,3]

10

```