# Latest

**URL:** https://discourse.julialang.org/latest.md?page=1711

[Latest](https://discourse.julialang.org/latest.md) · [Categories](https://discourse.julialang.org/categories.md) · [Tags](https://discourse.julialang.org/tags.md)

**Page:** 1712

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## [Create empty constraint with JuMP](https://discourse.julialang.org/t/create-empty-constraint-with-jump/41777)

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**Author:** [@Henrique\_Becker](https://discourse.julialang.org/u/Henrique_Becker)\
**Replies:** 11\
**Last updated:** [June 21, 2020, 1:55am UTC](https://discourse.julialang.org/t/create-empty-constraint-with-jump/41777 "2020-06-21T01:55:57Z")

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I have a part of my code in which it is simpler (far less ifs and edge cases) if I add empty constraints first and then, knowing all constraints I need are present in the model, change the coefficient of some variables i…

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## [Continuing bugs for SecondOrderODE problem solvers](https://discourse.julialang.org/t/continuing-bugs-for-secondorderode-problem-solvers/41559)

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**Author:** [@CosmoProf](https://discourse.julialang.org/u/CosmoProf)\
**Replies:** 34\
**Last updated:** [June 21, 2020, 12:43am UTC](https://discourse.julialang.org/t/continuing-bugs-for-secondorderode-problem-solvers/41559 "2020-06-21T00:43:22Z")

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Hi, working in DiffferentialEquations.jl, I find that a bunch of solvers don’t work with SecondOrderODE. This seems to be a bug at least a couple of years old, is there any way to use these solvers without reducing the p…

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## [Keyword arguments is causing allocations](https://discourse.julialang.org/t/keyword-arguments-is-causing-allocations/41798)

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**Author:** [@Ronis\_BR](https://discourse.julialang.org/u/Ronis_BR)\
**Replies:** 4\
**Last updated:** [June 21, 2020, 12:03am UTC](https://discourse.julialang.org/t/keyword-arguments-is-causing-allocations/41798 "2020-06-21T00:03:23Z")

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Hi! I am getting an allocation when using a keyword in the following MWE: julia\> function teste(a::AbstractVector{T}; b::Integer = 0, c::Integer = 0) where T return a\[1\] + b + c end teste (generic functio…

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## [Matrix to array of tuples: Avoiding many small allocations](https://discourse.julialang.org/t/matrix-to-array-of-tuples-avoiding-many-small-allocations/41796)

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**Author:** [@decardinb](https://discourse.julialang.org/u/decardinb)\
**Replies:** 2\
**Last updated:** [June 20, 2020, 11:35pm UTC](https://discourse.julialang.org/t/matrix-to-array-of-tuples-avoiding-many-small-allocations/41796 "2020-06-20T23:35:25Z")

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How do I convert a matrix to an array of tuples while avoiding many small allocations in a loop? My current code is function matrixtotuple(x::AbstractMatrix{T}) where T r,c = size(x) pts = Vector{Tuple}(undef,r) @ti…

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## [Frequent error](https://discourse.julialang.org/t/frequent-error/41784)

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**Author:** [@mayar](https://discourse.julialang.org/u/mayar)\
**Replies:** 4\
**Last updated:** [June 20, 2020, 10:29pm UTC](https://discourse.julialang.org/t/frequent-error/41784 "2020-06-20T22:29:01Z")

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Hello, I am new here and I do get this error often…I revise my code several time…I didnot specify the type of the variables in my function yet I get this error when I call the function…What is the meaning of this erro…

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## [Cannot install any Package](https://discourse.julialang.org/t/cannot-install-any-package/41787)

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**Author:** [@Geor](https://discourse.julialang.org/u/Geor)\
**Replies:** 8\
**Last updated:** [June 20, 2020, 6:59pm UTC](https://discourse.julialang.org/t/cannot-install-any-package/41787 "2020-06-20T18:59:50Z")

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Hello, I am new to Julia. I have not been able to install any package. I use the following: using Pkg Pkg.add(“IJulia”) And I get the below error: ERROR: SystemError: opening file “C:\\Users\\UserName\\.julia\\registri…

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## [Investigating numerical change in function return value between v1.4 vs v1.5](https://discourse.julialang.org/t/investigating-numerical-change-in-function-return-value-between-v1-4-vs-v1-5/41332)

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**Author:** [@jmert](https://discourse.julialang.org/u/jmert)\
**Replies:** 7\
**Last updated:** [June 20, 2020, 6:29pm UTC](https://discourse.julialang.org/t/investigating-numerical-change-in-function-return-value-between-v1-4-vs-v1-5/41332 "2020-06-20T18:29:33Z")

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I’ve got a function which is exhibiting a change to the numerical return value when comparing Julia versions 1.2 through 1.4 versus the 1.5beta (and master). I think this is actually an LLVM “error” (or a misunderstandin…

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## [Losing link between REPL and code window in Juno](https://discourse.julialang.org/t/losing-link-between-repl-and-code-window-in-juno/41778)

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**Author:** [@erlebach](https://discourse.julialang.org/u/erlebach)\
**Replies:** 1\
**Last updated:** [June 20, 2020, 4:16pm UTC](https://discourse.julialang.org/t/losing-link-between-repl-and-code-window-in-juno/41778 "2020-06-20T16:16:52Z")

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I have been comfortably been using Juno for Julia development and becoming happier with the workflow. Precompilation becoming less of an issue. However, this morning, I was working on Atom, and then took a break for abo…

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## [Finding MAP estimate in Turing?](https://discourse.julialang.org/t/finding-map-estimate-in-turing/41761)

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**Author:** [@dlakelan](https://discourse.julialang.org/u/dlakelan)\
**Replies:** 1\
**Last updated:** [June 20, 2020, 4:07am UTC](https://discourse.julialang.org/t/finding-map-estimate-in-turing/41761 "2020-06-20T04:07:19Z")

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I’m working on one of my Data Analysis tutorials. This one involves fitting a nonlinear function to an economic time series. The basic idea is that I have a radial basis function + some annual periodicity + a step funct…

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## [Reverse domain notation?](https://discourse.julialang.org/t/reverse-domain-notation/41774)

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**Author:** [@Gilga](https://discourse.julialang.org/u/Gilga)\
**Replies:** 3\
**Last updated:** [June 20, 2020, 4:04pm UTC](https://discourse.julialang.org/t/reverse-domain-notation/41774 "2020-06-20T16:04:34Z")

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The reverse domain notation is used by companies to name their Java packages. So I’m wondering if this would also be practical for Julia projects? Example: Imagine an organisation has a domain called mycompany.org and…

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## [Compiler optimization challenge: Bayer pattern image unpacking](https://discourse.julialang.org/t/compiler-optimization-challenge-bayer-pattern-image-unpacking/41779)

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**Author:** [@xor0110](https://discourse.julialang.org/u/xor0110)\
**Replies:** 0\
**Last updated:** [June 20, 2020, 3:16pm UTC](https://discourse.julialang.org/t/compiler-optimization-challenge-bayer-pattern-image-unpacking/41779 "2020-06-20T15:16:17Z")

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I’ve found an interesting example of a slightly convoluted for-loop that might be a good showcase of Julia’s ability to generate efficient code. I need help optimizing this code, though, because I’m not sure I have eithe…

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## [Deleteat!(trues(3), \[true, false, false\]) got "ArgumentError: indices must be unique and sorted"](https://discourse.julialang.org/t/deleteat-trues-3-true-false-false-got-argumenterror-indices-must-be-unique-and-sorted/41716)

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**Author:** [@Jieyi\_Xiong](https://discourse.julialang.org/u/Jieyi_Xiong)\
**Replies:** 18\
**Last updated:** [June 20, 2020, 2:00pm UTC](https://discourse.julialang.org/t/deleteat-trues-3-true-false-false-got-argumenterror-indices-must-be-unique-and-sorted/41716 "2020-06-20T14:00:14Z")

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I tested it in Julia 1.4.1 julia\> deleteat!(trues(3), \[true, false, false\]) ERROR: ArgumentError: indices must be unique and sorted Stacktrace: \[1\] deleteat!(::BitArray{1}, ::Array{Bool,1}) at ./bitarray.jl:976 \[2\] to…

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## [Anyone used PackageCompiler to build a distributable app with an Interact/Blink GUI?](https://discourse.julialang.org/t/anyone-used-packagecompiler-to-build-a-distributable-app-with-an-interact-blink-gui/39761)

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**Author:** [@mthelm85](https://discourse.julialang.org/u/mthelm85)\
**Replies:** 3\
**Last updated:** [June 20, 2020, 1:37pm UTC](https://discourse.julialang.org/t/anyone-used-packagecompiler-to-build-a-distributable-app-with-an-interact-blink-gui/39761 "2020-06-20T13:37:04Z")

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I have some code that I run a couple of times per month and I’d like to be able to build a GUI for it, compile it as an app, and then distribute the .exe to others in my organization (non-programmers) so that they can ma…

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## [Typeof(n\*n) in factorial](https://discourse.julialang.org/t/typeof-n-n-in-factorial/41700)

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**Author:** [@binarygcd](https://discourse.julialang.org/u/binarygcd)\
**Replies:** 29\
**Last updated:** [June 20, 2020, 12:01pm UTC](https://discourse.julialang.org/t/typeof-n-n-in-factorial/41700 "2020-06-20T12:01:29Z")

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The implementation of factorial in Base is function factorial(n::Integer) n \< 0 && throw(DomainError(n, "\`n\` must be nonnegative.")) f::typeof(n\*n) = 1 for i::typeof(n\*n) = 2:n f \*= i end ret…

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## [Construct an immutable type from a Dict](https://discourse.julialang.org/t/construct-an-immutable-type-from-a-dict/26709)

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**Author:** [@singularitti](https://discourse.julialang.org/u/singularitti)\
**Replies:** 9\
**Last updated:** [June 20, 2020, 9:55am UTC](https://discourse.julialang.org/t/construct-an-immutable-type-from-a-dict/26709 "2020-06-20T09:55:16Z")

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In development, I sometimes have an immutable type (for some reason, I do not want it to be mutable) with a large number of fields (5 in the following example), like struct A mass::Int velocity::String coordina…

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## [How do I find out, what makes GMP\_jll v6.2.0+0 downgrade to v6.1.2+5](https://discourse.julialang.org/t/how-do-i-find-out-what-makes-gmp-jll-v6-2-0-0-downgrade-to-v6-1-2-5/41763)

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**Author:** [@StevenSiew](https://discourse.julialang.org/u/StevenSiew)\
**Replies:** 2\
**Last updated:** [June 20, 2020, 8:50am UTC](https://discourse.julialang.org/t/how-do-i-find-out-what-makes-gmp-jll-v6-2-0-0-downgrade-to-v6-1-2-5/41763 "2020-06-20T08:50:44Z")

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How do I find out, what makes GMP v6.2.0+0 downgrade to v6.1.2+5 (@v1.4) pkg\> up Updating registry at \`~/.julia/registries/General\` Updating git-repo \`https://github.com/JuliaRegistries/General.git\` Updating gi…

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## [Histogram Equalization](https://discourse.julialang.org/t/histogram-equalization/41682)

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**Author:** [@Mohammed\_Sabiya](https://discourse.julialang.org/u/Mohammed_Sabiya)\
**Replies:** 28\
**Last updated:** [June 20, 2020, 8:25am UTC](https://discourse.julialang.org/t/histogram-equalization/41682 "2020-06-20T08:25:36Z")

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Hey, I’m trying a histogram equalization. I’m getting the following error. Can someone please help me with this? Thanks in advance!

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## [LU Decomposition - return permutation matrix instead of vector](https://discourse.julialang.org/t/lu-decomposition-return-permutation-matrix-instead-of-vector/41745)

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**Author:** [@ander](https://discourse.julialang.org/u/ander)\
**Replies:** 7\
**Last updated:** [June 20, 2020, 7:17am UTC](https://discourse.julialang.org/t/lu-decomposition-return-permutation-matrix-instead-of-vector/41745 "2020-06-20T07:17:53Z")

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Dear Community, Is there any way to return in Julia full permutation matrix instead of vector? using LinearAlgebra A = \[0 4 2; 10 2 1; 1 1 1\] L,U,P = lu(A) P is returned as \[2,1,3\]. However, I would like to have …

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## [Https://juliaobserver.com/ is completely black](https://discourse.julialang.org/t/https-juliaobserver-com-is-completely-black/41711)

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**Author:** [@schlichtanders](https://discourse.julialang.org/u/schlichtanders)\
**Replies:** 2\
**Last updated:** [June 20, 2020, 4:35am UTC](https://discourse.julialang.org/t/https-juliaobserver-com-is-completely-black/41711 "2020-06-20T04:35:51Z")

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Hi, I truly appreciate to support Black Lives Matter, however it would be great to have an option to somehow get to normal mode. Currently when going to julaobserver.com, I need to open HTML developer tools via inspect…

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## [Juliapackages and Juliaobserver](https://discourse.julialang.org/t/juliapackages-and-juliaobserver/41301)

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**Author:** [@sbacelar](https://discourse.julialang.org/u/sbacelar)\
**Replies:** 4\
**Last updated:** [June 20, 2020, 4:35am UTC](https://discourse.julialang.org/t/juliapackages-and-juliaobserver/41301 "2020-06-20T04:35:36Z")

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Are Juliapackages and Juliaobserver down?

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## [Juliapackages.com and juliaobserver "down"/black, anyone know why?](https://discourse.julialang.org/t/juliapackages-com-and-juliaobserver-down-black-anyone-know-why/41126)

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**Author:** [@Palli](https://discourse.julialang.org/u/Palli)\
**Replies:** 4\
**Last updated:** [June 20, 2020, 4:34am UTC](https://discourse.julialang.org/t/juliapackages-com-and-juliaobserver-down-black-anyone-know-why/41126 "2020-06-20T04:34:45Z")

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Maybe this is only happening for me, I can view source for both, but at least do not work in my Firefox on Linux.

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## [Do you suggest using ArrayFire?](https://discourse.julialang.org/t/do-you-suggest-using-arrayfire/41766)

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**Author:** [@BMval](https://discourse.julialang.org/u/BMval)\
**Replies:** 1\
**Last updated:** [June 20, 2020, 4:24am UTC](https://discourse.julialang.org/t/do-you-suggest-using-arrayfire/41766 "2020-06-20T04:24:32Z")

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I am new in GPU programming. Do you suggest or not using ArrayFire?

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## [Julia Intetnal](https://discourse.julialang.org/t/julia-intetnal/41768)

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**Author:** [@Ravinder\_Ram](https://discourse.julialang.org/u/Ravinder_Ram)\
**Replies:** 1\
**Last updated:** [June 20, 2020, 3:32am UTC](https://discourse.julialang.org/t/julia-intetnal/41768 "2020-06-20T03:32:50Z")

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I want to know each process from source code to native code… for ex:- “function sum(x,y) x+y end” how this source code compile?

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## [How to get the values in NDSparse as a matrix](https://discourse.julialang.org/t/how-to-get-the-values-in-ndsparse-as-a-matrix/41762)

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**Author:** [@Stephen](https://discourse.julialang.org/u/Stephen)\
**Replies:** 0\
**Last updated:** [June 20, 2020, 2:01am UTC](https://discourse.julialang.org/t/how-to-get-the-values-in-ndsparse-as-a-matrix/41762 "2020-06-20T02:01:07Z")

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julia\> Distance = loadndsparse("distance matrix.csv",indexcols = 1) 1-d NDSparse with 5 values (12 field named tuples): │ BO BR CO HA MN NA NH NL PO PR SP WO ─────┼───────────────────────────…

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## [Create a 2D array from a 1D array with reference](https://discourse.julialang.org/t/create-a-2d-array-from-a-1d-array-with-reference/41758)

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**Author:** [@sunjin](https://discourse.julialang.org/u/sunjin)\
**Replies:** 4\
**Last updated:** [June 20, 2020, 1:58am UTC](https://discourse.julialang.org/t/create-a-2d-array-from-a-1d-array-with-reference/41758 "2020-06-20T01:58:05Z")

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Hi I am trying to use FiniteDiff package to compute a gradient of a function with an N-vector as input and a scalar as output. I need to write the gradient (an N-vector) to a pre-allocated vector (supplied by an optimiz…

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## [Shared Memory with MPI.jl](https://discourse.julialang.org/t/shared-memory-with-mpi-jl/41747)

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**Author:** [@aditya\_314](https://discourse.julialang.org/u/aditya_314)\
**Replies:** 1\
**Last updated:** [June 20, 2020, 1:46am UTC](https://discourse.julialang.org/t/shared-memory-with-mpi-jl/41747 "2020-06-20T01:46:48Z")

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Sorry if this question is silly, I am new to parallel programming, I am using MPI.jl for writing distributed code. I want the processes to share an array. Is is possible to do this ? I know one way is to let one process …

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## [String getindex problem?](https://discourse.julialang.org/t/string-getindex-problem/41743)

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**Author:** [@Ronneesley](https://discourse.julialang.org/u/Ronneesley)\
**Replies:** 4\
**Last updated:** [June 20, 2020, 1:37am UTC](https://discourse.julialang.org/t/string-getindex-problem/41743 "2020-06-20T01:37:40Z")

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Why Julia have this accentuation problem? How to deal with this? julia\> length("cão") 3 julia\> "cão"\[3\] ERROR: StringIndexError("cão", 3) Stacktrace: \[1\] string\_index\_err(::String, ::Int64) at ./strings/string.jl:12 …

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## [Mismatch tree error when installing package in NFS location](https://discourse.julialang.org/t/mismatch-tree-error-when-installing-package-in-nfs-location/41757)

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**Author:** [@Fritz\_Ratnasamy](https://discourse.julialang.org/u/Fritz_Ratnasamy)\
**Replies:** 0\
**Last updated:** [June 20, 2020, 12:06am UTC](https://discourse.julialang.org/t/mismatch-tree-error-when-installing-package-in-nfs-location/41757 "2020-06-20T00:06:16Z")

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Issues occurs when installing packages (like OpenSpecFun, Zlib,CompilerSupportLibraries) or after package installation (Flux). \`\`using ("Flux") Installed OpenSpecFun\_jll ────────────── v0.5.3+3 Installed CodecZlib ─…

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## [Documentation "would like"](https://discourse.julialang.org/t/documentation-would-like/41683)

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**Author:** [@nevermind](https://discourse.julialang.org/u/nevermind)\
**Replies:** 9\
**Last updated:** [June 19, 2020, 11:16pm UTC](https://discourse.julialang.org/t/documentation-would-like/41683 "2020-06-19T23:16:11Z")

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Julia Documentation: Entering and Outputting Information In the Julia documentation section “Manual,” it would be practical if, after the subsection “Getting Started” and before the subsection “Variables,” there was a s…

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## [How do you open a "Choose File" prompt from Julia?](https://discourse.julialang.org/t/how-do-you-open-a-choose-file-prompt-from-julia/41748)

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**Author:** [@laut](https://discourse.julialang.org/u/laut)\
**Replies:** 5\
**Last updated:** [June 19, 2020, 11:12pm UTC](https://discourse.julialang.org/t/how-do-you-open-a-choose-file-prompt-from-julia/41748 "2020-06-19T23:12:53Z")

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I use file.choose() in R to open a “Choose File” window prompt to print a file path for files that I want to reference in my scripts. Is there a Julia equivalent for this?

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