# General Usage

**URL:** https://discourse.julialang.org/c/usage/6.md?page=446

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**Page:** 447

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## [Set Up Julia Pro](https://discourse.julialang.org/t/set-up-julia-pro/81530)

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**Author:** [@brett\_knoss](https://discourse.julialang.org/u/brett_knoss)\
**Replies:** 0\
**Last updated:** [May 23, 2022, 7:26pm UTC](https://discourse.julialang.org/t/set-up-julia-pro/81530 "2022-05-23T19:26:15Z")

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Is it still possible to set up JuliaPro? I’d like to use JuliaInXL. If this is not valid, is there another option to integrate Julia into Excel?

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## [JuliaInXl installation failed](https://discourse.julialang.org/t/juliainxl-installation-failed/60942)

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**Author:** [@DavyB](https://discourse.julialang.org/u/DavyB)\
**Replies:** 1\
**Last updated:** [May 23, 2022, 7:23pm UTC](https://discourse.julialang.org/t/juliainxl-installation-failed/60942 "2022-05-23T19:23:50Z")

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Dear all, I’m trying to install JuliaInXl without success. (Windows 10, Julia 1.5 and Office 2013) When I launch the command Pkg.add(“JuliaInXl”), I have the following error message : ERROR: The following package nam…

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## [How to use ldiv! correctly?](https://discourse.julialang.org/t/how-to-use-ldiv-correctly/81378)

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**Author:** [@Amro](https://discourse.julialang.org/u/Amro)\
**Replies:** 8\
**Last updated:** [May 23, 2022, 6:40pm UTC](https://discourse.julialang.org/t/how-to-use-ldiv-correctly/81378 "2022-05-23T18:40:12Z")

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How to solve the below error when using ldiv!? julia\> Sn=\[1 2 3;0 4 0;0 0 1\] 3×3 Matrix{Int64}: 1 2 3 0 4 0 0 0 1 julia\> Rn =\[1,2,3\] 3-element Vector{Int64}: 1 2 3 julia\> Qn= zeros(3) 3-element Vector{Floa…

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## [Vline and hline don't work with ticks=:native Plotly](https://discourse.julialang.org/t/vline-and-hline-dont-work-with-ticks-native-plotly/81509)

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**Author:** [@Wikunia](https://discourse.julialang.org/u/Wikunia)\
**Replies:** 1\
**Last updated:** [May 23, 2022, 5:34pm UTC](https://discourse.julialang.org/t/vline-and-hline-dont-work-with-ticks-native-plotly/81509 "2022-05-23T17:34:14Z")

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It seems like vline and hline have problems with ticks=:native in Plotly. using Plots plotly() plt1 = plot(ticks=:native) plot!(plt1, \[now()\], \[1\]) vline!(plt1, \[now()\]) Doesn’t work but without the vline! it does. The…

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## [If mutiple dispatch is done at compile time, wouldn't that make things faster?](https://discourse.julialang.org/t/if-mutiple-dispatch-is-done-at-compile-time-wouldnt-that-make-things-faster/81496)

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**Author:** [@thisismygitrepo](https://discourse.julialang.org/u/thisismygitrepo)\
**Replies:** 3\
**Last updated:** [May 23, 2022, 1:44pm UTC](https://discourse.julialang.org/t/if-mutiple-dispatch-is-done-at-compile-time-wouldnt-that-make-things-faster/81496 "2022-05-23T13:44:11Z")

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I’m not an expert in any sense, but can we not get MOAR speed if we don’t have to check types at runtime? So, if my code is statically styled, would that make it faster?

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## [ModelingToolkit, Symbolics, Complex{}](https://discourse.julialang.org/t/modelingtoolkit-symbolics-complex/81505)

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**Author:** [@Rohan\_Rajagopal](https://discourse.julialang.org/u/Rohan_Rajagopal)\
**Replies:** 2\
**Last updated:** [May 23, 2022, 1:12pm UTC](https://discourse.julialang.org/t/modelingtoolkit-symbolics-complex/81505 "2022-05-23T13:12:11Z")

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Greetings everyone, I have recently started using ModelingToolkit.jl. I am facing the following error with exponentiation, eqs\_1 = \[D(z1) ~ z1 \* ( μ + im \* ω\_1 - abs(z1)) + A \* ((cos(θ/ω\_2) + im\*sin(θ/ω\_2)) \* z2^μ), …

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## [Bug with @threads? Getting error iot instruction (core dumped)](https://discourse.julialang.org/t/bug-with-threads-getting-error-iot-instruction-core-dumped/81508)

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**Author:** [@davibarreira](https://discourse.julialang.org/u/davibarreira)\
**Replies:** 0\
**Last updated:** [May 23, 2022, 12:48pm UTC](https://discourse.julialang.org/t/bug-with-threads-getting-error-iot-instruction-core-dumped/81508 "2022-05-23T12:48:30Z")

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I’m facing a strange problem, and I’m having some trouble figuring out why it’s happening. I have a script that donwloads a pdf from an S3 bucket, extracts the text from the pdf and writes the document to a MongoDB, usi…

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## [Should large exponentials not yield Inf?](https://discourse.julialang.org/t/should-large-exponentials-not-yield-inf/81143)

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**Author:** [@nil](https://discourse.julialang.org/u/nil)\
**Replies:** 15\
**Last updated:** [May 23, 2022, 12:41pm UTC](https://discourse.julialang.org/t/should-large-exponentials-not-yield-inf/81143 "2022-05-23T12:41:40Z")

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I am wondering why some large exponentials yield wrong values, specifically always 1 or 0 julia\> 123^(456^789) 1 julia\> (0.1)^(456^789) 1.0 julia\> 456^789 0 This results in wrong values inside functions julia\> atan(…

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## [Problem with surface() when using plots.jl and gr() backend](https://discourse.julialang.org/t/problem-with-surface-when-using-plots-jl-and-gr-backend/81458)

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**Author:** [@mcreel](https://discourse.julialang.org/u/mcreel)\
**Replies:** 4\
**Last updated:** [May 23, 2022, 7:49am UTC](https://discourse.julialang.org/t/problem-with-surface-when-using-plots-jl-and-gr-backend/81458 "2022-05-23T07:49:59Z")

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I’m having a problem with a surface plot, using Plots.jl and the gr() backend. A minimal example is using Plots gr() #plotlyjs() x = range(0.9, length=100, stop=1.1) y= range(0.9, length=100, stop=1.1) p1 = surface(x, y…

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## [Question about round?](https://discourse.julialang.org/t/question-about-round/81479)

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**Author:** [@Raymond](https://discourse.julialang.org/u/Raymond)\
**Replies:** 3\
**Last updated:** [May 23, 2022, 1:33am UTC](https://discourse.julialang.org/t/question-about-round/81479 "2022-05-23T01:33:12Z")

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Dear all, In Matlab , \>\> round(2.5) ans = 3 But in Julia, julia\> round(2.5) 2.0 If I want to get the same result which is from Matlab, how to write the code in Julia?

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## [Three million linear regressions](https://discourse.julialang.org/t/three-million-linear-regressions/81439)

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**Author:** [@Baba\_Yara\_Fahiz](https://discourse.julialang.org/u/Baba_Yara_Fahiz)\
**Replies:** 4\
**Last updated:** [May 23, 2022, 12:52am UTC](https://discourse.julialang.org/t/three-million-linear-regressions/81439 "2022-05-23T00:52:39Z")

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I am running three million regressions of the form below and I feel like I am leaving a lot of performance on the table. Can I get some tips to help speed things up? function test\_1(data\_0) EignVectors = rand(100, 12) …

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## [Question about sort?](https://discourse.julialang.org/t/question-about-sort/81475)

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**Author:** [@Raymond](https://discourse.julialang.org/u/Raymond)\
**Replies:** 3\
**Last updated:** [May 22, 2022, 11:03pm UTC](https://discourse.julialang.org/t/question-about-sort/81475 "2022-05-22T23:03:50Z")

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Dear all, how to get the index when using sort in Julia? In Matlab ,we can get the index easily when using sort, \>\> A = \[7, 3, 6, 4\]; \>\> \[A, inds\] = sort(A) A = 3 4 6 7 inds = 2 4 3 …

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## [Joystick driver for Windows](https://discourse.julialang.org/t/joystick-driver-for-windows/81473)

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**Author:** [@ufechner7](https://discourse.julialang.org/u/ufechner7)\
**Replies:** 6\
**Last updated:** [May 22, 2022, 10:37pm UTC](https://discourse.julialang.org/t/joystick-driver-for-windows/81473 "2022-05-22T22:37:42Z")

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I am quite happy with the Joystick driver for Linux GitHub - ufechner7/Joysticks.jl: Joystick interface for Julia , but now people also want to have it on Windows. That seams to be difficult. As far as I understand ther…

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## [Can \`where\` constrain type parameters that are instances, like \`where {T isa Symbol}\`](https://discourse.julialang.org/t/can-where-constrain-type-parameters-that-are-instances-like-where-t-isa-symbol/81443)

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**Author:** [@Benny](https://discourse.julialang.org/u/Benny)\
**Replies:** 6\
**Last updated:** [May 22, 2022, 6:56pm UTC](https://discourse.julialang.org/t/can-where-constrain-type-parameters-that-are-instances-like-where-t-isa-symbol/81443 "2022-05-22T18:56:43Z")

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where clauses can constrain type parameters that are types e.g. where T \<: Number, but I’m interested in constraining instances e.g. where T isa Symbol vs. where T isa Integer, which is not valid syntax. Is there a way t…

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## [Julia user's guide for the positive semidefinite program with variables in {-1,1}](https://discourse.julialang.org/t/julia-users-guide-for-the-positive-semidefinite-program-with-variables-in-1-1/81460)

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**Author:** [@Huyen26n](https://discourse.julialang.org/u/Huyen26n)\
**Replies:** 1\
**Last updated:** [May 22, 2022, 5:31pm UTC](https://discourse.julialang.org/t/julia-users-guide-for-the-positive-semidefinite-program-with-variables-in-1-1/81460 "2022-05-22T17:31:25Z")

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Dear all, I am using Julia for the first time to work on the positive semidefinite program. I’m trying to solve the PSD with variables in {-1,1}. I don’t understand how to write objective functions or variables, … I wis…

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## [Question about Julia zeros matrix?](https://discourse.julialang.org/t/question-about-julia-zeros-matrix/81350)

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**Author:** [@Raymond](https://discourse.julialang.org/u/Raymond)\
**Replies:** 12\
**Last updated:** [May 22, 2022, 3:06pm UTC](https://discourse.julialang.org/t/question-about-julia-zeros-matrix/81350 "2022-05-22T15:06:58Z")

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Dear all, In matlab, we can add complex values into zeros matrix, but in Julia I cannot .Can you help me to modify my codes to add complex values into zeros matrix in Julia? This is the matlab code. \>\> A = zeros(2, 2)…

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## [Printing in a background process](https://discourse.julialang.org/t/printing-in-a-background-process/81453)

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**Author:** [@FedeClaudi](https://discourse.julialang.org/u/FedeClaudi)\
**Replies:** 10\
**Last updated:** [May 22, 2022, 12:51pm UTC](https://discourse.julialang.org/t/printing-in-a-background-process/81453 "2022-05-22T12:51:07Z")

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Hi everyone, I’m trying to do something that feels like should be easy but I can’t figure it out. Basically, let’s say I have a function (doer) which takes a while to run and I want to have another function printer pri…

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## [Linting stage in CI pipeline - which to use and how?](https://discourse.julialang.org/t/linting-stage-in-ci-pipeline-which-to-use-and-how/80697)

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**Author:** [@FireCrumb](https://discourse.julialang.org/u/FireCrumb)\
**Replies:** 13\
**Last updated:** [May 22, 2022, 10:30am UTC](https://discourse.julialang.org/t/linting-stage-in-ci-pipeline-which-to-use-and-how/80697 "2022-05-22T10:30:04Z")

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Hello, I have a CI/CD pipeline in GitLab, and I want to run a lintig stage to fail the build on detected bugs. What is the proper way to do this? Found Lint.jl but it’s abandoned (last update 2019) Found StaticLint.jl …

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## [What does the REPL keybinding ctrl + \< + t correspond to?](https://discourse.julialang.org/t/what-does-the-repl-keybinding-ctrl-t-correspond-to/81424)

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**Author:** [@jishnub](https://discourse.julialang.org/u/jishnub)\
**Replies:** 2\
**Last updated:** [May 22, 2022, 10:14am UTC](https://discourse.julialang.org/t/what-does-the-repl-keybinding-ctrl-t-correspond-to/81424 "2022-05-22T10:14:42Z")

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Because of a weird keyboard layout, I often end up pressing ctrl + \< + t instead of ctrl + shift + t, and I obtain the following output: julia\> \<┌ Error: Error in the keymap │ exception = │ EOFError: read end of fi…

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## [Problem after discretizing a PDE to ODE and solve with DifferentialEquations.jl](https://discourse.julialang.org/t/problem-after-discretizing-a-pde-to-ode-and-solve-with-differentialequations-jl/81451)

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**Author:** [@Molox](https://discourse.julialang.org/u/Molox)\
**Replies:** 1\
**Last updated:** [May 22, 2022, 9:42am UTC](https://discourse.julialang.org/t/problem-after-discretizing-a-pde-to-ode-and-solve-with-differentialequations-jl/81451 "2022-05-22T09:42:01Z")

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Hi, I was reading https://www.stochasticlifestyle.com/solving-systems-stochastic-pdes-using-gpus-julia/ And I would like to know if it is possible to discretize a 4th derivative PDE to ODE: ddt(u) = ddddx(u) and solve w…

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## [Type of composition of functions is not predictable](https://discourse.julialang.org/t/type-of-composition-of-functions-is-not-predictable/81446)

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**Author:** [@Veenty](https://discourse.julialang.org/u/Veenty)\
**Replies:** 1\
**Last updated:** [May 22, 2022, 6:08am UTC](https://discourse.julialang.org/t/type-of-composition-of-functions-is-not-predictable/81446 "2022-05-22T06:08:15Z")

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I’m trying to figure out why the type of this function is not predictable function η\_const(r, η\_) if r\>=1 return convert( typeof(r), 0.0) elseif r\<=0.8 return convert( typeof(r), 1.0) els…

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## [@everywhere and PackageCompiler build\_executable()](https://discourse.julialang.org/t/everywhere-and-packagecompiler-build-executable/16121)

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**Author:** [@waldoc](https://discourse.julialang.org/u/waldoc)\
**Replies:** 1\
**Last updated:** [May 21, 2022, 9:33am UTC](https://discourse.julialang.org/t/everywhere-and-packagecompiler-build-executable/16121 "2022-05-21T09:33:44Z")

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I am trying to build an executable using a package I created. The code makes use of pmap to run on multiple workers. I created a new module with the function name as per PackageCompiler recommendations and compiled with…

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## [Understand why type stability depends on number of methods](https://discourse.julialang.org/t/understand-why-type-stability-depends-on-number-of-methods/81434)

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**Author:** [@bgctw](https://discourse.julialang.org/u/bgctw)\
**Replies:** 2\
**Last updated:** [May 22, 2022, 12:01am UTC](https://discourse.julialang.org/t/understand-why-type-stability-depends-on-number-of-methods/81434 "2022-05-22T00:01:50Z")

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I am reading the of Julia book of Kwong (@tk3369) and Karpinski 2020 and like to use the singleton type dispatch pattern. However, when I check type stability (on Julia 1.7.3), I find that it suddenly fails when more me…

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## [Make documentation for package under Julia 1.8beta3](https://discourse.julialang.org/t/make-documentation-for-package-under-julia-1-8beta3/81437)

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**Author:** [@Joris\_Pinkse](https://discourse.julialang.org/u/Joris_Pinkse)\
**Replies:** 0\
**Last updated:** [May 21, 2022, 9:53pm UTC](https://discourse.julialang.org/t/make-documentation-for-package-under-julia-1-8beta3/81437 "2022-05-21T21:53:05Z")

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I’m working on developing a new package that uses some features only available in Julia 1.8. It runs fine under the nightly, except that the documentation (Documenter) does not get deployed because the package requires …

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## [How to define and integrate a HamiltonianProblem?](https://discourse.julialang.org/t/how-to-define-and-integrate-a-hamiltonianproblem/81303)

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**Author:** [@cdawg](https://discourse.julialang.org/u/cdawg)\
**Replies:** 5\
**Last updated:** [May 21, 2022, 6:51pm UTC](https://discourse.julialang.org/t/how-to-define-and-integrate-a-hamiltonianproblem/81303 "2022-05-21T18:51:49Z")

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Dear friends. I have a hamiltonian for the cart and pole system which is a standard problem in RL. Lagrangian version shown here, I just legendre transformed it. I don’t need a full solution. I just want to step it forw…

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## [Plot image in memory how to get at a pixel on a line](https://discourse.julialang.org/t/plot-image-in-memory-how-to-get-at-a-pixel-on-a-line/81312)

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**Author:** [@anon69491625](https://discourse.julialang.org/u/anon69491625)\
**Replies:** 1\
**Last updated:** [May 21, 2022, 6:07pm UTC](https://discourse.julialang.org/t/plot-image-in-memory-how-to-get-at-a-pixel-on-a-line/81312 "2022-05-21T18:07:42Z")

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hi all I am thinking about how to access a memory location that represents a pixel on an image. So in the image below the first pixel of the first line or the first pixel of the 2nd row line. I’d like to keep it si…

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## [How to read without blocking](https://discourse.julialang.org/t/how-to-read-without-blocking/81409)

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**Author:** [@ufechner7](https://discourse.julialang.org/u/ufechner7)\
**Replies:** 6\
**Last updated:** [May 21, 2022, 1:41pm UTC](https://discourse.julialang.org/t/how-to-read-without-blocking/81409 "2022-05-21T13:41:31Z")

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How can I read from an input device on Linux in a non-blocking way, perhaps with a timeout? I have this function: function read\_event(js::JSDevice) event = read(js.device, sizeof(JSEvent); all = false) if sizeo…

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## [From recursive to iterative](https://discourse.julialang.org/t/from-recursive-to-iterative/81411)

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**Author:** [@rocco\_sprmnt21](https://discourse.julialang.org/u/rocco_sprmnt21)\
**Replies:** 0\
**Last updated:** [May 21, 2022, 10:56am UTC](https://discourse.julialang.org/t/from-recursive-to-iterative/81411 "2022-05-21T10:56:06Z")

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Given a table nxn and a starting position, it is required to determine a sequence of steps / moves that allow you to go through all the cells once and only once. The allowed moves are those that move vertically and hori…

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## [Documentation about using anonymous and named functions with pmap](https://discourse.julialang.org/t/documentation-about-using-anonymous-and-named-functions-with-pmap/19337)

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**Author:** [@zsunberg](https://discourse.julialang.org/u/zsunberg)\
**Replies:** 9\
**Last updated:** [May 21, 2022, 8:23am UTC](https://discourse.julialang.org/t/documentation-about-using-anonymous-and-named-functions-with-pmap/19337 "2022-05-21T08:23:14Z")

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I noticed that anonymous functions behave differently from regular functions w.r.t. serialization and code availability on other processes. e.g., when julia is run with multiple processes, f(x) = x^2 pmap(f, 1:10) thro…

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## [Module correctly loaded from LOAD\_PATH but still getting a dependencies warning](https://discourse.julialang.org/t/module-correctly-loaded-from-load-path-but-still-getting-a-dependencies-warning/58087)

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**Author:** [@essenciary](https://discourse.julialang.org/u/essenciary)\
**Replies:** 1\
**Last updated:** [May 21, 2022, 3:02am UTC](https://discourse.julialang.org/t/module-correctly-loaded-from-load-path-but-still-getting-a-dependencies-warning/58087 "2022-05-21T03:02:27Z")

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I have a folder added to LOAD\_PATH, and in this folder the TestsController.jl module. In another file I have using TestsController. Everything works as expected, but upon loading the app/script I’m getting a warning abou…

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