# General Usage

**URL:** https://discourse.julialang.org/c/usage/6.md?page=21

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**Page:** 22

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## [Eigenvalues of large, sparse matrices](https://discourse.julialang.org/t/eigenvalues-of-large-sparse-matrices/135208)

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**Author:** [@pjk](https://discourse.julialang.org/u/pjk)\
**Replies:** 11\
**Last updated:** [January 23, 2026, 7:24pm UTC](https://discourse.julialang.org/t/eigenvalues-of-large-sparse-matrices/135208 "2026-01-23T19:24:55Z")

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Hi all, I am working on a problem which involves the calculation of the eigenvalues (specifically the spectral radius) of matrices with a particular structure. These are specifically sparse, asymmetric matrices with bin…

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## [Terminal interaction and precompile times](https://discourse.julialang.org/t/terminal-interaction-and-precompile-times/135225)

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**Author:** [@paulmelis](https://discourse.julialang.org/u/paulmelis)\
**Replies:** 3\
**Last updated:** [January 23, 2026, 5:07pm UTC](https://discourse.julialang.org/t/terminal-interaction-and-precompile-times/135225 "2026-01-23T17:07:02Z")

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Somewhat related to the other threads on precompile times (such as thread and thread), I was wondering about (perceived) long precompilation for very simple and common operations. These seem to have gotten worse as well,…

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## [How to extract the \*\*numerical differential equations\*\* from a model I built with ModelingToolkit.?](https://discourse.julialang.org/t/how-to-extract-the-numerical-differential-equations-from-a-model-i-built-with-modelingtoolkit/135221)

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**Author:** [@andreas1](https://discourse.julialang.org/u/andreas1)\
**Replies:** 1\
**Last updated:** [January 23, 2026, 1:44pm UTC](https://discourse.julialang.org/t/how-to-extract-the-numerical-differential-equations-from-a-model-i-built-with-modelingtoolkit/135221 "2026-01-23T13:44:54Z")

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hy, I want to extract the numerical differential equations from a model I built with ModelingToolkit. For example: @mtkbuild dgl = System(vcat(eqs\_1, eq2), t) Define problem prob = ODEProblem(dgl, bcs, tspan) Now I w…

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## [Pass Clustering.Hclust to Makie.dendrogram](https://discourse.julialang.org/t/pass-clustering-hclust-to-makie-dendrogram/135143)

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**Author:** [@alequa](https://discourse.julialang.org/u/alequa)\
**Replies:** 4\
**Last updated:** [January 22, 2026, 5:34pm UTC](https://discourse.julialang.org/t/pass-clustering-hclust-to-makie-dendrogram/135143 "2026-01-22T17:34:14Z")

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Hello, I would like to know how to convert the HClust object to a data format that can be processed by the dendrogram recipe for Makie. There is a quite long pull-request history for the dendrogram recipe, and it seems…

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## [GLMakie on vscode remote backend](https://discourse.julialang.org/t/glmakie-on-vscode-remote-backend/135195)

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**Author:** [@freeman](https://discourse.julialang.org/u/freeman)\
**Replies:** 4\
**Last updated:** [January 22, 2026, 4:05pm UTC](https://discourse.julialang.org/t/glmakie-on-vscode-remote-backend/135195 "2026-01-22T16:05:32Z")

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Does anybody know if it’s possible to use GLMakie with vscode remote backend? CairoMaike works. When I try, I get this: Failed to precompile GLMakie \[e9467ef8-e4e7-5192-8a1a-b1aee30e663a\] to "/home/user/.julia/compiled…

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## [Simple \`redirect\_stdout\` example](https://discourse.julialang.org/t/simple-redirect-stdout-example/135204)

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**Author:** [@mattsignorelli](https://discourse.julialang.org/u/mattsignorelli)\
**Replies:** 5\
**Last updated:** [January 22, 2026, 2:02pm UTC](https://discourse.julialang.org/t/simple-redirect-stdout-example/135204 "2026-01-22T14:02:45Z")

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I am struggling to get any example with redirect\_stdout to work. There isn’t any documentation on it. E.g. julia\> f, io = mktemp(); julia\> fout = open(f, "w+"); julia\> redirect\_stdout(fout) do println("Hello!")…

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## [Convergence of SDE solvers](https://discourse.julialang.org/t/convergence-of-sde-solvers/135179)

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**Author:** [@diffeqslvr](https://discourse.julialang.org/u/diffeqslvr)\
**Replies:** 6\
**Last updated:** [January 22, 2026, 11:22am UTC](https://discourse.julialang.org/t/convergence-of-sde-solvers/135179 "2026-01-22T11:22:52Z")

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I am wondering how to make sure that an SDE solver has converged on a trajectory level. In other words, I want to make sure that I have chosen abstol and reltol small enough. What I would do in the deterministic case is…

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## [Solving an SDE with a Continuous Callback](https://discourse.julialang.org/t/solving-an-sde-with-a-continuous-callback/135180)

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**Author:** [@diffeqslvr](https://discourse.julialang.org/u/diffeqslvr)\
**Replies:** 5\
**Last updated:** [January 22, 2026, 8:51am UTC](https://discourse.julialang.org/t/solving-an-sde-with-a-continuous-callback/135180 "2026-01-22T08:51:49Z")

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I am solving a stochastic differential equation with a ContinuousCallback. Every time the continuous callback is activated, I modify my state vector discontinuously. All the randomness comes from a phase, which follows …

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## [\`@infiltry\` usage](https://discourse.julialang.org/t/infiltry-usage/135198)

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**Author:** [@Alec\_Loudenback](https://discourse.julialang.org/u/Alec_Loudenback)\
**Replies:** 2\
**Last updated:** [January 22, 2026, 8:21am UTC](https://discourse.julialang.org/t/infiltry-usage/135198 "2026-01-22T08:21:35Z")

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I’m exploring Infiltrator.jl and I am not clear on the use case or purpose of @infiltry. I thought that it would help me debug by catching the state of the code when the exception occurred, but this does not seem to be t…

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## [General-relativistic coordinates transformation support](https://discourse.julialang.org/t/general-relativistic-coordinates-transformation-support/135196)

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**Author:** [@raman\_kumar](https://discourse.julialang.org/u/raman_kumar)\
**Replies:** 0\
**Last updated:** [January 22, 2026, 1:08am UTC](https://discourse.julialang.org/t/general-relativistic-coordinates-transformation-support/135196 "2026-01-22T01:08:43Z")

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I am looking for package that supports general-relativistic coordinates transformation to Cartesian etc. I would like to transform the following coordinates to Cartesian and vice versa. What will be the code if i have to…

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## [What's the fastest way to fill an array with random bits without using private Random.jl internals?](https://discourse.julialang.org/t/whats-the-fastest-way-to-fill-an-array-with-random-bits-without-using-private-random-jl-internals/135089)

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**Author:** [@npbarnes](https://discourse.julialang.org/u/npbarnes)\
**Replies:** 16\
**Last updated:** [January 21, 2026, 6:59pm UTC](https://discourse.julialang.org/t/whats-the-fastest-way-to-fill-an-array-with-random-bits-without-using-private-random-jl-internals/135089 "2026-01-21T18:59:25Z")

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Suppose I have an array of type e.g. Array{Float64} and I want to fill it with random bits as fast as possible. Note that that’s different from filling it with random floats between 0 and 1. A straight forward way to do …

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## [Sometimes cannot reclaim memory by manual GC.gc()](https://discourse.julialang.org/t/sometimes-cannot-reclaim-memory-by-manual-gc-gc/135158)

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**Author:** [@WalterMadelim](https://discourse.julialang.org/u/WalterMadelim)\
**Replies:** 9\
**Last updated:** [January 21, 2026, 10:09am UTC](https://discourse.julialang.org/t/sometimes-cannot-reclaim-memory-by-manual-gc-gc/135158 "2026-01-21T10:09:24Z")

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Edit: Please see the #7 post directly if you’re interested. Thanks. The idea is: I at first create a Vector v = Vector{Matrix{Float64}}(undef, 100); Then I need to fill it with some concrete objects (here are matric…

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## [Idiomatic evaluate for scalar, allocate and broadcast for array?](https://discourse.julialang.org/t/idiomatic-evaluate-for-scalar-allocate-and-broadcast-for-array/135147)

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**Author:** [@bremez](https://discourse.julialang.org/u/bremez)\
**Replies:** 7\
**Last updated:** [January 21, 2026, 7:01am UTC](https://discourse.julialang.org/t/idiomatic-evaluate-for-scalar-allocate-and-broadcast-for-array/135147 "2026-01-21T07:01:58Z")

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In several cases I’ve come across the following pattern: function f(x; kwargs...) #intense pre-computation that depend on kwargs but not x result = 0.0 \* x; # one way to preallocate for e.g. x::Vector, but not for scala…

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## [External model inputs with time delay using DDEproblem](https://discourse.julialang.org/t/external-model-inputs-with-time-delay-using-ddeproblem/135059)

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**Author:** [@amaliebm](https://discourse.julialang.org/u/amaliebm)\
**Replies:** 1\
**Last updated:** [January 21, 2026, 5:04am UTC](https://discourse.julialang.org/t/external-model-inputs-with-time-delay-using-ddeproblem/135059 "2026-01-21T05:04:34Z")

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How do you add time delays to the external model inputs using ModelingToolkit and DDEProblem? In the example below, adding a time delay to the input Q, gives the error “KeyError: key Q not found” using ModelingToolkit,…

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## [Problems trying to compile with JuliaC.jl: "Parameters not found"](https://discourse.julialang.org/t/problems-trying-to-compile-with-juliac-jl-parameters-not-found/135168)

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**Author:** [@JJMerelo](https://discourse.julialang.org/u/JJMerelo)\
**Replies:** 0\
**Last updated:** [January 20, 2026, 7:33pm UTC](https://discourse.julialang.org/t/problems-trying-to-compile-with-juliac-jl-parameters-not-found/135168 "2026-01-20T19:33:31Z")

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I’m trying t compile a script using JuliaC.jl and julia version 1.12.3, and I’m getting this error: ◓ Compiling... Activating project at \`/home/jmerelo/Code/julia/BraveNewAlgorithm.jl\` ◓ Compiling...ArgumentError: Pack…

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## [How to change repl keybindings](https://discourse.julialang.org/t/how-to-change-repl-keybindings/135167)

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**Author:** [@jar1](https://discourse.julialang.org/u/jar1)\
**Replies:** 1\
**Last updated:** [January 20, 2026, 7:22pm UTC](https://discourse.julialang.org/t/how-to-change-repl-keybindings/135167 "2026-01-20T19:22:38Z")

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REPL: allow editing current input in editor (via Meta-e) by rfourquet · Pull Request #33759 · JuliaLang/julia · GitHub uses Meta+e for edit command line in editor. I want to use Ctrl+xCtrl+e for that because that’s what…

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## [Issues customizing \`JULIAUP\_DEPOT\_PATH\` for VSCode](https://discourse.julialang.org/t/issues-customizing-juliaup-depot-path-for-vscode/135152)

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**Author:** [@jlchan](https://discourse.julialang.org/u/jlchan)\
**Replies:** 2\
**Last updated:** [January 19, 2026, 11:37pm UTC](https://discourse.julialang.org/t/issues-customizing-juliaup-depot-path-for-vscode/135152 "2026-01-19T23:37:53Z")

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I’m having some trouble customizing JULIA\_DEPOT\_PATH through juliaup based on the juliaup repo is that Before installing Julia/juliaup, I add export JULIAUP\_DEPOT\_PATH=/workspace/.julia to my ~/.bashrc file. I then in…

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## [How to render string to html / escape for html](https://discourse.julialang.org/t/how-to-render-string-to-html-escape-for-html/135146)

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**Author:** [@jar1](https://discourse.julialang.org/u/jar1)\
**Replies:** 1\
**Last updated:** [January 19, 2026, 9:55pm UTC](https://discourse.julialang.org/t/how-to-render-string-to-html-escape-for-html/135146 "2026-01-19T21:55:40Z")

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How do I render a string into html? For example s = "x \< y"; render(s) should become "x &lt; y". This works but it’s a little verbose: using HypertextLiteral let io = IOBuffer() print(io, HypertextLiteral.Result(H…

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## [Documenter.jl says \`git remote\` failed - why?](https://discourse.julialang.org/t/documenter-jl-says-git-remote-failed-why/135142)

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**Author:** [@floswald](https://discourse.julialang.org/u/floswald)\
**Replies:** 9\
**Last updated:** [January 19, 2026, 8:49pm UTC](https://discourse.julialang.org/t/documenter-jl-says-git-remote-failed-why/135142 "2026-01-19T20:49:48Z")

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I don’t understand this error reported by Documenter.jl - in particular, why is Documenter prefixing my PATH with the strange artifact? why: floswald@PTL11077 ~/.j/d/P/docs (main)\> /Users/floswald/.julia/artifacts/9a049…

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## [Identical input in Zygote leads to different outputs](https://discourse.julialang.org/t/identical-input-in-zygote-leads-to-different-outputs/135120)

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**Author:** [@Chrysoberyl](https://discourse.julialang.org/u/Chrysoberyl)\
**Replies:** 1\
**Last updated:** [January 19, 2026, 12:27am UTC](https://discourse.julialang.org/t/identical-input-in-zygote-leads-to-different-outputs/135120 "2026-01-19T00:27:54Z")

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In this script, the forward pass has no error: using GNNGraphs, GraphNeuralNetworks, NNlib, Flux graph = GNNHeteroGraph( Dict( (:A, :a, :B) =\> (\[1, 2\], \[3, 4\]), (:B, :a, :A) =\> (\[1\], \[2\]), ); …

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## [How to get the device name and the number of Compute units when using oneAPI.jl or AMDGPU.jl?](https://discourse.julialang.org/t/how-to-get-the-device-name-and-the-number-of-compute-units-when-using-oneapi-jl-or-amdgpu-jl/128361)

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**Author:** [@bpsomu](https://discourse.julialang.org/u/bpsomu)\
**Replies:** 1\
**Last updated:** [January 18, 2026, 5:31pm UTC](https://discourse.julialang.org/t/how-to-get-the-device-name-and-the-number-of-compute-units-when-using-oneapi-jl-or-amdgpu-jl/128361 "2026-01-18T17:31:01Z")

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I am working on making a GPU vendor agnostic code with KerneAbstractions.jl. I am getting the device name with device = CUDA.device() and getting the number of Streaming Multiprocessors with sm\_count = CUDA.attribute(…

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## [Documenter.jl: Running external commands asynchronously in \`@example\` blocks](https://discourse.julialang.org/t/documenter-jl-running-external-commands-asynchronously-in-example-blocks/135085)

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**Author:** [@klafyvel](https://discourse.julialang.org/u/klafyvel)\
**Replies:** 1\
**Last updated:** [January 18, 2026, 4:16pm UTC](https://discourse.julialang.org/t/documenter-jl-running-external-commands-asynchronously-in-example-blocks/135085 "2026-01-18T16:16:15Z")

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Hello, I am trying to run the following @example block in a Documenter page: pinocchio = PipeBuffer() listener = run(\`go-sendxmpp -n -p plopiplop -u pinocchio@localhost -l\`, devnull, pinocchio, stderr, wait = false) Bu…

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## [Is the allocation from @time the total at the end, or during a calculation?](https://discourse.julialang.org/t/is-the-allocation-from-time-the-total-at-the-end-or-during-a-calculation/135111)

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**Author:** [@dankelley](https://discourse.julialang.org/u/dankelley)\
**Replies:** 4\
**Last updated:** [January 17, 2026, 7:02pm UTC](https://discourse.julialang.org/t/is-the-allocation-from-time-the-total-at-the-end-or-during-a-calculation/135111 "2026-01-17T19:02:52Z")

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As a newcomer to Julia, I am writing some code to work with oceanographic datasets that are fairly large. A test file is 138MiB in size but the instrument that creates the data can emit files up to about 4GiB in size. …

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## [How to arrange a package with submodules and multiple files?](https://discourse.julialang.org/t/how-to-arrange-a-package-with-submodules-and-multiple-files/21709)

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**Author:** [@Gu\_Junhua](https://discourse.julialang.org/u/Gu_Junhua)\
**Replies:** 7\
**Last updated:** [January 16, 2026, 10:17pm UTC](https://discourse.julialang.org/t/how-to-arrange-a-package-with-submodules-and-multiple-files/21709 "2026-01-16T22:17:14Z")

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Say I’m writing a package P, which contains two sub-modules M1 and M2. Both submodules share some common codes, so I extract the common codes and wrap it in another sub module C I decide to split the codes into four fil…

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## [Standard function name to skip intermediate step piping getindex call into vec](https://discourse.julialang.org/t/standard-function-name-to-skip-intermediate-step-piping-getindex-call-into-vec/135088)

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**Author:** [@croberts](https://discourse.julialang.org/u/croberts)\
**Replies:** 4\
**Last updated:** [January 16, 2026, 8:23pm UTC](https://discourse.julialang.org/t/standard-function-name-to-skip-intermediate-step-piping-getindex-call-into-vec/135088 "2026-01-16T20:23:08Z")

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I am wondering about Julia conventions - is there a function or kwarg for skipping an intermediate type when taking an array through getindex and then vec? More concretely, suppose we are doing a getindex call on a Spar…

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## [Revise.jl never works for me](https://discourse.julialang.org/t/revise-jl-never-works-for-me/135072)

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**Author:** [@fireking07](https://discourse.julialang.org/u/fireking07)\
**Replies:** 6\
**Last updated:** [January 16, 2026, 11:53am UTC](https://discourse.julialang.org/t/revise-jl-never-works-for-me/135072 "2026-01-16T11:53:40Z")

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I have been trying to configure Revise.jl on VS Code (I am new to VS Code since I found Julia to be fiddly with emacs). I enabled using Revise.jl to be executed when I start a new REPL. I am developing a package. Essent…

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## [Save module/function using PackageCompiler](https://discourse.julialang.org/t/save-module-function-using-packagecompiler/135064)

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**Author:** [@stelmo](https://discourse.julialang.org/u/stelmo)\
**Replies:** 7\
**Last updated:** [January 16, 2026, 1:01am UTC](https://discourse.julialang.org/t/save-module-function-using-packagecompiler/135064 "2026-01-16T01:01:46Z")

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Is it possible to save the compiled version of a function, f, which is not in a package, using PackageCompiler? For example, suppose I have a file model.jl which contains: module Model include("func.jl") end f(rand(2…

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## [Best practice for calling Julia functions via API](https://discourse.julialang.org/t/best-practice-for-calling-julia-functions-via-api/135086)

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**Author:** [@Chrysoberyl](https://discourse.julialang.org/u/Chrysoberyl)\
**Replies:** 0\
**Last updated:** [January 15, 2026, 8:04pm UTC](https://discourse.julialang.org/t/best-practice-for-calling-julia-functions-via-api/135086 "2026-01-15T20:04:30Z")

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In my setup, a Julia function calls a C/Rust function play(agent, environment), which spawns some threads, and call functions on agent. agent and environment are Julia objects. Each of these foreign threads gets registe…

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## [Unit testing iterators](https://discourse.julialang.org/t/unit-testing-iterators/135078)

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**Author:** [@Tamas\_Papp](https://discourse.julialang.org/u/Tamas_Papp)\
**Replies:** 0\
**Last updated:** [January 15, 2026, 1:49pm UTC](https://discourse.julialang.org/t/unit-testing-iterators/135078 "2026-01-15T13:49:12Z")

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Is there a package to test that a type implements the iteration interface correctly? Just some basic sanity checks, eg if get the size/eltype traits, check that they are consistent, compare repeatedly calling iterate un…

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## [Bonito.jl color picker](https://discourse.julialang.org/t/bonito-jl-color-picker/135075)

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**Author:** [@gdkrmr](https://discourse.julialang.org/u/gdkrmr)\
**Replies:** 0\
**Last updated:** [January 15, 2026, 1:07pm UTC](https://discourse.julialang.org/t/bonito-jl-color-picker/135075 "2026-01-15T13:07:06Z")

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I want to enable users to change a color in a Bonito.jl app. Is there a preexisting color picker? Also: If I have a simple TextField, is it safe to parse this as colorant"$(textfield.value)"?

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