# General Usage

**URL:** https://discourse.julialang.org/c/usage/6.md?page=612

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

**Page:** 613

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## [Concatenate markdown strings](https://discourse.julialang.org/t/concatenate-markdown-strings/59385)

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**Author:** [@PhilipDLoewen](https://discourse.julialang.org/u/PhilipDLoewen)\
**Replies:** 5\
**Last updated:** [April 16, 2021, 2:43pm UTC](https://discourse.julialang.org/t/concatenate-markdown-strings/59385 "2021-04-16T14:43:30Z")

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For ordinary strings, "as"\*"df" produces "asdf". For markdown strings, md"as"\*md"df" produces an error. So does md\_str("as"\*"df"). Is there any way to reinterpret a string with a complicated history as markdown? Eventua…

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## [Run function with delay](https://discourse.julialang.org/t/run-function-with-delay/59404)

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**Author:** [@Javise](https://discourse.julialang.org/u/Javise)\
**Replies:** 1\
**Last updated:** [April 16, 2021, 2:42pm UTC](https://discourse.julialang.org/t/run-function-with-delay/59404 "2021-04-16T14:42:26Z")

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Hello, How can I make a function run automatically X seconds after another function has been run (with Pluto) ? Thank you

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## [What are the rules for qualified/unqualified symbols in macros? (or is it a bug?)](https://discourse.julialang.org/t/what-are-the-rules-for-qualified-unqualified-symbols-in-macros-or-is-it-a-bug/59293)

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**Author:** [@mobius-eng](https://discourse.julialang.org/u/mobius-eng)\
**Replies:** 5\
**Last updated:** [April 16, 2021, 2:20pm UTC](https://discourse.julialang.org/t/what-are-the-rules-for-qualified-unqualified-symbols-in-macros-or-is-it-a-bug/59293 "2021-04-16T14:20:46Z")

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Let’s say I want to automate making lots of very similar looking, but semantically distinct types: macro make\_struct(arg) quote struct $(esc(arg)) x end export $(esc(arg)) end…

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## [JSON3 filtering a JSON object](https://discourse.julialang.org/t/json3-filtering-a-json-object/59412)

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**Author:** [@mthelm85](https://discourse.julialang.org/u/mthelm85)\
**Replies:** 4\
**Last updated:** [April 16, 2021, 1:20pm UTC](https://discourse.julialang.org/t/json3-filtering-a-json-object/59412 "2021-04-16T13:20:14Z")

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How can I do this? using JSON3 json = """ { "type": "FeatureCollection", "features": \[ {"type":"Feature","geometry":{"type":"Polygon","coordinates":\[\[\[-120.8519857235256,49.00031611973458\],\[-121.7597100…

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## [DifferentialEquations.jl: running out of memory with large system size ODE](https://discourse.julialang.org/t/differentialequations-jl-running-out-of-memory-with-large-system-size-ode/59357)

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**Author:** [@Joh11](https://discourse.julialang.org/u/Joh11)\
**Replies:** 11\
**Last updated:** [April 16, 2021, 10:53am UTC](https://discourse.julialang.org/t/differentialequations-jl-running-out-of-memory-with-large-system-size-ode/59357 "2021-04-16T10:53:59Z")

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Hi everyone, I need to solve a first order, homogeneous, time independent ODE on a relatively big system size (3 \\times 3 \\times 144 \\times 144=186,624 dimensions). I had previously made a crude fixed step Dormand Princ…

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## [NeuralPDE/PINN: System of Equations Substitution and Inequalities](https://discourse.julialang.org/t/neuralpde-pinn-system-of-equations-substitution-and-inequalities/59379)

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**Author:** [@James\_Gorman](https://discourse.julialang.org/u/James_Gorman)\
**Replies:** 1\
**Last updated:** [April 16, 2021, 8:57am UTC](https://discourse.julialang.org/t/neuralpde-pinn-system-of-equations-substitution-and-inequalities/59379 "2021-04-16T08:57:41Z")

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After stumbling across physics-informed neural networks a couple weeks ago, and realizing julia had a framework for solving them, I realized I might have found an open-source method for solving PDEs that was powerful and…

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## [Precompiling most packages fails in Atom/Juno with 1.6.0](https://discourse.julialang.org/t/precompiling-most-packages-fails-in-atom-juno-with-1-6-0/59308)

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**Author:** [@maxkapur](https://discourse.julialang.org/u/maxkapur)\
**Replies:** 12\
**Last updated:** [April 16, 2021, 6:24am UTC](https://discourse.julialang.org/t/precompiling-most-packages-fails-in-atom-juno-with-1-6-0/59308 "2021-04-16T06:24:01Z")

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I wish I could narrow down the problem more precisely than this, but since updating to 1.6.0, I have begun to encounter very strange behavior when calling using Polyhedra (and various other packages) from the REPL embedd…

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## [Does @allocated not work with multithreading?](https://discourse.julialang.org/t/does-allocated-not-work-with-multithreading/59354)

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**Author:** [@nmayhall-vt](https://discourse.julialang.org/u/nmayhall-vt)\
**Replies:** 3\
**Last updated:** [April 16, 2021, 5:12am UTC](https://discourse.julialang.org/t/does-allocated-not-work-with-multithreading/59354 "2021-04-16T05:12:38Z")

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I’ve been trying to better undertstand how to find allocations in my code, and I stumbled on this simple MWE which either exposes some limitation of @allocated, or (more likely) a limitation of my understanding. functio…

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## [Syntax error](https://discourse.julialang.org/t/syntax-error/59378)

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**Author:** [@trodger88](https://discourse.julialang.org/u/trodger88)\
**Replies:** 1\
**Last updated:** [April 16, 2021, 1:42am UTC](https://discourse.julialang.org/t/syntax-error/59378 "2021-04-16T01:42:42Z")

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Using Gtk b=GtkBuilder(filename=“/home/tjr/Glade/test.glade”) win=b\[“Test Window”\] showall(win) When I try to run I get syntax: extra token “Gtk” after end of expression top-level scope at test.jl:1 include\_string…

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## [Use of Timer](https://discourse.julialang.org/t/use-of-timer/59350)

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**Author:** [@Javise](https://discourse.julialang.org/u/Javise)\
**Replies:** 3\
**Last updated:** [April 15, 2021, 8:14pm UTC](https://discourse.julialang.org/t/use-of-timer/59350 "2021-04-15T20:14:13Z")

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Hello, I would like to make a text appear and have each letter appear at X seconds intervals. I think it is possible to do this with the Timer function but I don’t know how to use it. I had thought of using an array tha…

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## [MbedTLS 1.0.2 failed to load on Julia 1.5.2 (solved by downgrading to MbedTLS 0.7.0)](https://discourse.julialang.org/t/mbedtls-1-0-2-failed-to-load-on-julia-1-5-2-solved-by-downgrading-to-mbedtls-0-7-0/47430)

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**Author:** [@awasserman](https://discourse.julialang.org/u/awasserman)\
**Replies:** 7\
**Last updated:** [April 15, 2021, 7:17pm UTC](https://discourse.julialang.org/t/mbedtls-1-0-2-failed-to-load-on-julia-1-5-2-solved-by-downgrading-to-mbedtls-0-7-0/47430 "2021-04-15T19:17:32Z")

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I had an issue with installing a few packages that ultimately depended on MbedTLS (via HTTP). Adding and building MbedTLS 1.0.2 seemed to work fine, but while precompiling it raised the following error with undefined s…

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## [Problem in understanding how to load data to estimate covariance matrix](https://discourse.julialang.org/t/problem-in-understanding-how-to-load-data-to-estimate-covariance-matrix/59365)

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**Author:** [@Shahal](https://discourse.julialang.org/u/Shahal)\
**Replies:** 2\
**Last updated:** [April 15, 2021, 6:06pm UTC](https://discourse.julialang.org/t/problem-in-understanding-how-to-load-data-to-estimate-covariance-matrix/59365 "2021-04-15T18:06:40Z")

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0 My aim is to estimate the covariance matrix using 10 Forex high-frequency data. I found the Julia package, HighFrequencyCovariance, HighFrequencyCovariance.jl - Algorithms for efficiently estimating covariance matric…

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## [How do model a sub type that can fall under two different abstract types?](https://discourse.julialang.org/t/how-do-model-a-sub-type-that-can-fall-under-two-different-abstract-types/59355)

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**Author:** [@anon60034542](https://discourse.julialang.org/u/anon60034542)\
**Replies:** 2\
**Last updated:** [April 15, 2021, 4:31pm UTC](https://discourse.julialang.org/t/how-do-model-a-sub-type-that-can-fall-under-two-different-abstract-types/59355 "2021-04-15T16:31:45Z")

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Suppose you’re building a medieval role playing game, you’re going to have weapons of different types, so you’ll create an abstract type called Weapon: abstract type GameObject end abstract type Weapon \<: GameObject end…

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## [Gadfly and controling colors and label](https://discourse.julialang.org/t/gadfly-and-controling-colors-and-label/59290)

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**Author:** [@Oto\_Brzobohaty](https://discourse.julialang.org/u/Oto_Brzobohaty)\
**Replies:** 9\
**Last updated:** [April 15, 2021, 4:15pm UTC](https://discourse.julialang.org/t/gadfly-and-controling-colors-and-label/59290 "2021-04-15T16:15:25Z")

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I like the syntax of plotting using Gadfly, but it is relatively far from my experience with plotting with Matlab and Plots. I wonder if there is an easy way how to control the colors and labels in the following example…

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## [Exact numerical logging](https://discourse.julialang.org/t/exact-numerical-logging/58766)

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**Author:** [@Tamas\_Papp](https://discourse.julialang.org/u/Tamas_Papp)\
**Replies:** 25\
**Last updated:** [April 15, 2021, 4:05pm UTC](https://discourse.julialang.org/t/exact-numerical-logging/58766 "2021-04-15T16:05:12Z")

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I have a long-running calculation, for which want to emit a log that allows recovery of exact numerical values, so that I can restart or debug the calculation. The typical logged item can be thought of as a (possibly nes…

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## [Why use subtypes instead of traits and duck typing?](https://discourse.julialang.org/t/why-use-subtypes-instead-of-traits-and-duck-typing/59146)

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**Author:** [@regier2302](https://discourse.julialang.org/u/regier2302)\
**Replies:** 32\
**Last updated:** [April 15, 2021, 3:58pm UTC](https://discourse.julialang.org/t/why-use-subtypes-instead-of-traits-and-duck-typing/59146 "2021-04-15T15:58:50Z")

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I have been tinkering with Julia and I am now trying to design a moderate-sized project. However, I have been struggling to come up with a type hierarchy and I realized that, in Julia, I don’t know why you should subtype…

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## [Performance difference between optional args and keyword args](https://discourse.julialang.org/t/performance-difference-between-optional-args-and-keyword-args/59272)

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**Author:** [@amrods](https://discourse.julialang.org/u/amrods)\
**Replies:** 8\
**Last updated:** [April 15, 2021, 2:26pm UTC](https://discourse.julialang.org/t/performance-difference-between-optional-args-and-keyword-args/59272 "2021-04-15T14:26:30Z")

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Is there any (theoretical) difference in performance between functions defined with optional arguments and functions defined with keyword arguments? The manual says: Keyword arguments behave quite differently from ordi…

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## [Help me with @eval](https://discourse.julialang.org/t/help-me-with-eval/59341)

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**Author:** [@Impressium](https://discourse.julialang.org/u/Impressium)\
**Replies:** 5\
**Last updated:** [April 15, 2021, 2:04pm UTC](https://discourse.julialang.org/t/help-me-with-eval/59341 "2021-04-15T14:04:56Z")

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Hey all :slight\_smile: Below I wrote a minimal working example of what I’m trying to do. But I can’t get it to work. I’m doing something wrong. julia\> mutable struct Test field\_1 field\_2 …

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## [How to save Conda path change permanently?](https://discourse.julialang.org/t/how-to-save-conda-path-change-permanently/59340)

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**Author:** [@jolly](https://discourse.julialang.org/u/jolly)\
**Replies:** 0\
**Last updated:** [April 15, 2021, 1:21pm UTC](https://discourse.julialang.org/t/how-to-save-conda-path-change-permanently/59340 "2021-04-15T13:21:55Z")

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Hello, I am using some Python packages, such as numpy. I am calling it in Julia using PyCall. Two things seems suboptimal and I cannot figure out how to solve it: The Python packages are not found and do not get imp…

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## [Small union type failure](https://discourse.julialang.org/t/small-union-type-failure/18640)

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**Author:** [@cstjean](https://discourse.julialang.org/u/cstjean)\
**Replies:** 15\
**Last updated:** [April 15, 2021, 10:52am UTC](https://discourse.julialang.org/t/small-union-type-failure/18640 "2021-04-15T10:52:05Z")

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I thought that missing wasn’t treated specially, and that all small type unions would be Unioned. Have I misunderstood? julia\> struct Blag end julia\> typeof(\[ifelse(randn() \< 0, 1.0, Missing()) for \_ in 1:100\]) Array{U…

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## [Problem with Qt dependency of Plots.jl](https://discourse.julialang.org/t/problem-with-qt-dependency-of-plots-jl/58765)

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**Author:** [@erans](https://discourse.julialang.org/u/erans)\
**Replies:** 2\
**Last updated:** [April 15, 2021, 10:37am UTC](https://discourse.julialang.org/t/problem-with-qt-dependency-of-plots-jl/58765 "2021-04-15T10:37:14Z")

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Hello, I’m having an issue with a package I’m developing that depends on Plots.jl. The gist is, that when I dev this package then I get a precompilation error: ERROR: LoadError: LoadError: InitError: could not load li…

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## [Is there already an auto-conversion macro for function signatures?](https://discourse.julialang.org/t/is-there-already-an-auto-conversion-macro-for-function-signatures/59320)

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**Author:** [@jules](https://discourse.julialang.org/u/jules)\
**Replies:** 0\
**Last updated:** [April 15, 2021, 9:05am UTC](https://discourse.julialang.org/t/is-there-already-an-auto-conversion-macro-for-function-signatures/59320 "2021-04-15T09:05:25Z")

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I’ve thought about making a macro to auto-convert a more general type-signature to a specific one. Is there already something like this? The reason is that often, a function realistically should only work for a couple o…

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## [After update, CUDA.jl not working](https://discourse.julialang.org/t/after-update-cuda-jl-not-working/59318)

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**Author:** [@Ferran\_Mazzanti](https://discourse.julialang.org/u/Ferran_Mazzanti)\
**Replies:** 0\
**Last updated:** [April 15, 2021, 8:57am UTC](https://discourse.julialang.org/t/after-update-cuda-jl-not-working/59318 "2021-04-15T08:57:58Z")

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Hi, yesterday I read the message about the new CUDA package. Today I just did an update (julia 1.6.0 on ubuntu mate 20.04) and the CUDA package did upgrade. After that julia\> using CUDA julia\> CUDA.zeros(10) ┌ Error:…

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## [Softmax applied to arrays?](https://discourse.julialang.org/t/softmax-applied-to-arrays/59299)

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**Author:** [@dadada\_dadada](https://discourse.julialang.org/u/dadada_dadada)\
**Replies:** 2\
**Last updated:** [April 14, 2021, 9:56pm UTC](https://discourse.julialang.org/t/softmax-applied-to-arrays/59299 "2021-04-14T21:56:01Z")

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Hi everybody, I would like to repeatedly apply (a variation of) the softmax function to parts of an array. I would like to know if there are ways to leverage packages like Tullio, Yeppp, and other Julianic features as …

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## [What does GKSwstype do?](https://discourse.julialang.org/t/what-does-gkswstype-do/59226)

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**Author:** [@feanor12](https://discourse.julialang.org/u/feanor12)\
**Replies:** 3\
**Last updated:** [April 14, 2021, 7:53pm UTC](https://discourse.julialang.org/t/what-does-gkswstype-do/59226 "2021-04-14T19:53:58Z")

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I can see GKSwstype being used in a lot of workarounds for Plots/GR. Is there documentation on what the different options do? I just found a list of options in the C code of GR and I think it sets the (interactive) ren…

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## [The REPL and character display](https://discourse.julialang.org/t/the-repl-and-character-display/59269)

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**Author:** [@Hermes](https://discourse.julialang.org/u/Hermes)\
**Replies:** 5\
**Last updated:** [April 14, 2021, 7:23pm UTC](https://discourse.julialang.org/t/the-repl-and-character-display/59269 "2021-04-14T19:23:09Z")

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What should I install so that in Julia REPL, symbols and special characters can be correctly seen. In the figure I show what happens: However in VS Code Terminal, the characters and symbols are correctly seen jul…

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## [DifferentialEquations.jl Solution handling with ArrayPartition?](https://discourse.julialang.org/t/differentialequations-jl-solution-handling-with-arraypartition/59279)

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**Author:** [@Antomek](https://discourse.julialang.org/u/Antomek)\
**Replies:** 1\
**Last updated:** [April 14, 2021, 3:07pm UTC](https://discourse.julialang.org/t/differentialequations-jl-solution-handling-with-arraypartition/59279 "2021-04-14T15:07:19Z")

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Hello everyone, I have a very simple question, yet one I can’t seem to work out easily. Is there a straighforward way to access the different parts of an ArrayPartition solution that we have obtained with DifferentialE…

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## [Ordered TOML?](https://discourse.julialang.org/t/ordered-toml/59278)

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**Author:** [@Amval](https://discourse.julialang.org/u/Amval)\
**Replies:** 3\
**Last updated:** [April 14, 2021, 2:28pm UTC](https://discourse.julialang.org/t/ordered-toml/59278 "2021-04-14T14:28:03Z")

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Hello everyone, I am on the process of upgrading to Julia 1.6, which includes a TOML package as part of the base libraries. Before, I was using my own TOMLpackage, forked from here to returned an OrderedDict instead of…

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## [Julia on Raspberry Pi: error building HDF5 package](https://discourse.julialang.org/t/julia-on-raspberry-pi-error-building-hdf5-package/29903)

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**Author:** [@sairus7](https://discourse.julialang.org/u/sairus7)\
**Replies:** 47\
**Last updated:** [April 14, 2021, 2:25pm UTC](https://discourse.julialang.org/t/julia-on-raspberry-pi-error-building-hdf5-package/29903 "2021-04-14T14:25:19Z")

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I’ve installed Julia language on Raspberry Pi as mentioned here: But then trying to \]add HDF5 the following error appears: (v1.2) pkg\> add HDF5 Resolving package versions... Installed CMakeWrapper ─────── v0.2.3 In…

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## [Separate array elements without adding spaces](https://discourse.julialang.org/t/separate-array-elements-without-adding-spaces/59191)

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**Author:** [@Arif\_Baloch](https://discourse.julialang.org/u/Arif_Baloch)\
**Replies:** 4\
**Last updated:** [April 14, 2021, 2:20pm UTC](https://discourse.julialang.org/t/separate-array-elements-without-adding-spaces/59191 "2021-04-14T14:20:28Z")

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can anyone tell me how to separate the elements of an array automatically.e.g A=\[1234\] to A=\[1 2 3 4\] without giving any space

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