# General Usage

**URL:** https://discourse.julialang.org/c/usage/6.md?page=669

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

**Page:** 670

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## [Edit PNG PLTE](https://discourse.julialang.org/t/edit-png-plte/51305)

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**Author:** [@HugoTrentesaux](https://discourse.julialang.org/u/HugoTrentesaux)\
**Replies:** 6\
**Last updated:** [December 7, 2020, 2:05pm UTC](https://discourse.julialang.org/t/edit-png-plte/51305 "2020-12-07T14:05:05Z")

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The PNG format specifies an optional color palette (PLTE chunk). I want to edit this palette with Julia but do not find a starting point. Is there an existing library which provides this kind of “low level” control over …

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## [Types, strange behavior](https://discourse.julialang.org/t/types-strange-behavior/51384)

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**Author:** [@rapasite](https://discourse.julialang.org/u/rapasite)\
**Replies:** 2\
**Last updated:** [December 7, 2020, 10:38am UTC](https://discourse.julialang.org/t/types-strange-behavior/51384 "2020-12-07T10:38:44Z")

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Julia Version 1.5.3 (2020-11-09) Hi, looking at this vector=\[\[1,2\],\[3,\[4,5\]\]\] vector\[1\] typeof(vector\[1\]) julia\> vector=\[\[1,2\],\[3,\[4,5\]\]\] 2-element Array{Array{Any,1},1}: \[1, 2\] \[3, \[4, 5\]\] julia\> vector\[1\] 2-eleme…

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## [Incremental compilation may be fatally broken for this module](https://discourse.julialang.org/t/incremental-compilation-may-be-fatally-broken-for-this-module/51373)

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**Author:** [@Ravinder\_Ram](https://discourse.julialang.org/u/Ravinder_Ram)\
**Replies:** 1\
**Last updated:** [December 7, 2020, 8:01am UTC](https://discourse.julialang.org/t/incremental-compilation-may-be-fatally-broken-for-this-module/51373 "2020-12-07T08:01:37Z")

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warning why this come? how to remove it

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## [Why Can not My Recursive Function Work?](https://discourse.julialang.org/t/why-can-not-my-recursive-function-work/51378)

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**Author:** [@KyleJT](https://discourse.julialang.org/u/KyleJT)\
**Replies:** 2\
**Last updated:** [December 7, 2020, 7:04am UTC](https://discourse.julialang.org/t/why-can-not-my-recursive-function-work/51378 "2020-12-07T07:04:35Z")

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I want to write a function to add all the arguments, using a recursive function as followed: function add\_Varargs(b...) if length(b) == 1 return b else t=b\[1:end-1\] println(b\[end\]) …

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## [How do I install node.js to use jupyter?](https://discourse.julialang.org/t/how-do-i-install-node-js-to-use-jupyter/51372)

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**Author:** [@brett\_knoss](https://discourse.julialang.org/u/brett_knoss)\
**Replies:** 1\
**Last updated:** [December 7, 2020, 5:28am UTC](https://discourse.julialang.org/t/how-do-i-install-node-js-to-use-jupyter/51372 "2020-12-07T05:28:56Z")

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I need node.js to access extensions in jupyter, as well as to execute certain types of plots in Jupyter or Pluto. How do I add this?

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## [DIfferentialEquations and GPU](https://discourse.julialang.org/t/differentialequations-and-gpu/21219)

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**Author:** [@fedoroff](https://discourse.julialang.org/u/fedoroff)\
**Replies:** 15\
**Last updated:** [December 7, 2020, 2:44am UTC](https://discourse.julialang.org/t/differentialequations-and-gpu/21219 "2020-12-07T02:44:24Z")

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Hello, According to the following blog post http://www.stochasticlifestyle.com/solving-systems-stochastic-pdes-using-gpus-julia/ it is very easy to turn on GPU parallelism with DifferentialEquations.jl. The only thing o…

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## [Meshfree methods](https://discourse.julialang.org/t/meshfree-methods/51247)

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**Author:** [@FrootLoops](https://discourse.julialang.org/u/FrootLoops)\
**Replies:** 4\
**Last updated:** [December 6, 2020, 7:55pm UTC](https://discourse.julialang.org/t/meshfree-methods/51247 "2020-12-06T19:55:27Z")

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Hi, are there any known packages or modifications for meshfree methods like IGA Galerkin? I cannot find much in the internet. Maybe someone already modified JuAFEM for these kind of applications?

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## [UndefVarError: P not defined](https://discourse.julialang.org/t/undefvarerror-p-not-defined/51358)

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**Author:** [@Ernesto\_Diaz](https://discourse.julialang.org/u/Ernesto_Diaz)\
**Replies:** 2\
**Last updated:** [December 6, 2020, 6:59pm UTC](https://discourse.julialang.org/t/undefvarerror-p-not-defined/51358 "2020-12-06T18:59:21Z")

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qp=0.6 function Plist(xi,qp) for i=0.001:5:xi push!(P,qp\*i) end return P end P=Plist(240,qp) Previous code return: UndefVarError: P not defined Stracktrace: \[1\]Plist(::Int64, ::Float64) at .\\In\[12\]:5 \[2…

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## [Where pre-compiled package stored in computer?](https://discourse.julialang.org/t/where-pre-compiled-package-stored-in-computer/51355)

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**Author:** [@Ravinder\_Ram](https://discourse.julialang.org/u/Ravinder_Ram)\
**Replies:** 1\
**Last updated:** [December 6, 2020, 6:50pm UTC](https://discourse.julialang.org/t/where-pre-compiled-package-stored-in-computer/51355 "2020-12-06T18:50:57Z")

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whenever pre-compiling happen where compiled package is store can i see it?

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## [\*\* incremental compilation may be fatally broken for this module \*\*](https://discourse.julialang.org/t/incremental-compilation-may-be-fatally-broken-for-this-module/31443)

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**Author:** [@Qiyamah](https://discourse.julialang.org/u/Qiyamah)\
**Replies:** 3\
**Last updated:** [December 6, 2020, 5:58pm UTC](https://discourse.julialang.org/t/incremental-compilation-may-be-fatally-broken-for-this-module/31443 "2020-12-06T17:58:01Z")

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This keeps popping up, when I try to redefine the same macro or function in a module? Is this ok? It tells me that I have overwritten a method, which I did intentionally… Thanks

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## [How confgurate IJulia with python 3.9-64?](https://discourse.julialang.org/t/how-confgurate-ijulia-with-python-3-9-64/51354)

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**Author:** [@HerAdri](https://discourse.julialang.org/u/HerAdri)\
**Replies:** 0\
**Last updated:** [December 6, 2020, 5:57pm UTC](https://discourse.julialang.org/t/how-confgurate-ijulia-with-python-3-9-64/51354 "2020-12-06T17:57:48Z")

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How to configure Ijulia to run correctly with python 3.9-64? Jupyter notebook works fine with python installation C:\\Users\\user\>py -0 Installed Pythons found by py Launcher for Windows -3.9-64 \* C:\\Users\\user\>jupyter …

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## [@code\_lowered vs @code\_typed](https://discourse.julialang.org/t/code-lowered-vs-code-typed/51346)

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**Author:** [@cscherrer](https://discourse.julialang.org/u/cscherrer)\
**Replies:** 9\
**Last updated:** [December 6, 2020, 5:12pm UTC](https://discourse.julialang.org/t/code-lowered-vs-code-typed/51346 "2020-12-06T17:12:20Z")

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Where can I find documentation of the difference between these? The main Julia docs aren’t very clear about it. I have an example of two functions where @code\_typed is identical, but @code\_lowered is not. There’s a diff…

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## [Csv error reading numbers as string](https://discourse.julialang.org/t/csv-error-reading-numbers-as-string/51341)

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**Author:** [@mayar](https://discourse.julialang.org/u/mayar)\
**Replies:** 16\
**Last updated:** [December 6, 2020, 3:16pm UTC](https://discourse.julialang.org/t/csv-error-reading-numbers-as-string/51341 "2020-12-06T15:16:26Z")

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Hello all, I have always used csv.read for my csv files but now after the new julia update , I have troubles with csv.read it sometimes reads numbers as integers and sometime doesnot how do I avoid this problem ? tha…

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## [Kron and shared data, not the right amount of sharing?](https://discourse.julialang.org/t/kron-and-shared-data-not-the-right-amount-of-sharing/48080)

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**Author:** [@malacroi](https://discourse.julialang.org/u/malacroi)\
**Replies:** 1\
**Last updated:** [December 6, 2020, 2:34pm UTC](https://discourse.julialang.org/t/kron-and-shared-data-not-the-right-amount-of-sharing/48080 "2020-12-06T14:34:30Z")

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The kron function on vectors seems to be inappropriately holding on to its input. As a simple example, the input s = \[2,5\]; k=kron(s,\[3,1\]); push!(s,4) produces the error: cannot resize array with shared data Stackt…

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## [Better compression for JLD2 (Discussion)](https://discourse.julialang.org/t/better-compression-for-jld2-discussion/51306)

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**Author:** [@JonasIsensee](https://discourse.julialang.org/u/JonasIsensee)\
**Replies:** 2\
**Last updated:** [December 6, 2020, 2:25pm UTC](https://discourse.julialang.org/t/better-compression-for-jld2-discussion/51306 "2020-12-06T14:25:03Z")

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Hi all, I’m working on bringing faster / more flexible compression to JLD2. Currently you can do @save "test.jld2" {compress=true} a b c and JLD2 will then compress sufficiently large arrays using CodecZlib. This wor…

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## [Best Data format for Tabular Data plus Vector](https://discourse.julialang.org/t/best-data-format-for-tabular-data-plus-vector/51315)

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**Author:** [@Jake](https://discourse.julialang.org/u/Jake)\
**Replies:** 3\
**Last updated:** [December 6, 2020, 2:22pm UTC](https://discourse.julialang.org/t/best-data-format-for-tabular-data-plus-vector/51315 "2020-12-06T14:22:08Z")

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Coming from a background in Matlab, where I do mostly signal processing kinds of things, and am considering switching to Julia, I was looking for good alternatives for data storage in Julia. The type of data I would lik…

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## [Fractional MIME types? what about style/class attribute values?](https://discourse.julialang.org/t/fractional-mime-types-what-about-style-class-attribute-values/51263)

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**Author:** [@cce](https://discourse.julialang.org/u/cce)\
**Replies:** 2\
**Last updated:** [December 6, 2020, 2:12pm UTC](https://discourse.julialang.org/t/fractional-mime-types-what-about-style-class-attribute-values/51263 "2020-12-06T14:12:15Z")

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Hello. I’m finalizing the implementation of an HTML generation library, HypertextLiteral.jl based upon @mbostock’s Hypertext Literal (HTM). The goal of this is to provide server-side HTML generation, using Julia interpo…

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## [Loading setup script for JuliaCall in R not working](https://discourse.julialang.org/t/loading-setup-script-for-juliacall-in-r-not-working/51285)

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**Author:** [@clement](https://discourse.julialang.org/u/clement)\
**Replies:** 6\
**Last updated:** [December 6, 2020, 12:44am UTC](https://discourse.julialang.org/t/loading-setup-script-for-juliacall-in-r-not-working/51285 "2020-12-06T00:44:49Z")

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Hi everybody, I managed to successfully install Julia on my Ubuntu machine into a specific folder. Path to the Julia bin is /home/clement/Julia\_download/julia-1.5.3/bin Now, the goal is to call or run julia in R. I h…

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## [Documentation fails to deploy](https://discourse.julialang.org/t/documentation-fails-to-deploy/51340)

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**Author:** [@Christopher\_Fisher](https://discourse.julialang.org/u/Christopher_Fisher)\
**Replies:** 0\
**Last updated:** [December 6, 2020, 10:51am UTC](https://discourse.julialang.org/t/documentation-fails-to-deploy/51340 "2020-12-06T10:51:25Z")

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Hi all- I am trying to add documentation to a repo according to the instructions for Documenter.jl. I added a key to github with read/write access, and the corresponding key to Travis-CI. Unfortunately, it returns the e…

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## [Very fancy package updating 1.6](https://discourse.julialang.org/t/very-fancy-package-updating-1-6/51227)

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**Author:** [@PetrKryslUCSD](https://discourse.julialang.org/u/PetrKryslUCSD)\
**Replies:** 27\
**Last updated:** [December 6, 2020, 9:38am UTC](https://discourse.julialang.org/t/very-fancy-package-updating-1-6/51227 "2020-12-06T09:38:15Z")

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Animated progress. Beautiful!

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## [Programatically get return type of \`broadcast\`?](https://discourse.julialang.org/t/programatically-get-return-type-of-broadcast/51071)

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**Author:** [@jdh62043](https://discourse.julialang.org/u/jdh62043)\
**Replies:** 10\
**Last updated:** [December 6, 2020, 8:07am UTC](https://discourse.julialang.org/t/programatically-get-return-type-of-broadcast/51071 "2020-12-06T08:07:09Z")

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Is there some way to get what a call to broadcast would return, possibly similar to how promote works? An example of what I need is something like this: using StaticArrays a1 = SA\_F32\[1, 2, 3\] # SArray{Tuple{3}, Float3…

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## [ODEs using Element-wise vector multiplication](https://discourse.julialang.org/t/odes-using-element-wise-vector-multiplication/51332)

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**Author:** [@jonlym](https://discourse.julialang.org/u/jonlym)\
**Replies:** 2\
**Last updated:** [December 6, 2020, 3:36am UTC](https://discourse.julialang.org/t/odes-using-element-wise-vector-multiplication/51332 "2020-12-06T03:36:35Z")

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Hi All, I’m new to Julia. I would like to solve a series of ODEs but noticed the solution does not update when I use element-wise vector multiplication (see the code snippet and plot below). Why does f1! solve correctly…

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## [Memory usage with large JSON](https://discourse.julialang.org/t/memory-usage-with-large-json/51277)

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**Author:** [@evanfields](https://discourse.julialang.org/u/evanfields)\
**Replies:** 5\
**Last updated:** [December 6, 2020, 12:45am UTC](https://discourse.julialang.org/t/memory-usage-with-large-json/51277 "2020-12-06T00:45:19Z")

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I was using JSON to parse a large (1.6 GB) JSON file, and the memory usage was surprising. More surprisingly, perhaps, was that even after removing the reference to the parsed object and garbage collecting, the memory us…

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## [RecipesBase: Reuse a @series and use/work with provided limits](https://discourse.julialang.org/t/recipesbase-reuse-a-series-and-use-work-with-provided-limits/51290)

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**Author:** [@kellertuer](https://discourse.julialang.org/u/kellertuer)\
**Replies:** 2\
**Last updated:** [December 5, 2020, 9:15am UTC](https://discourse.julialang.org/t/recipesbase-reuse-a-series-and-use-work-with-provided-limits/51290 "2020-12-05T09:15:34Z")

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I am starting to really appreciate how RecipesBase works, now that I slowly understand the scheme. Maybe for now this is limited to user recipes, but nevertheless, really neat! Currently I have one point left, where I a…

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## [JLD2: How to @load a file from string](https://discourse.julialang.org/t/jld2-how-to-load-a-file-from-string/51214)

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**Author:** [@neo\_abs](https://discourse.julialang.org/u/neo_abs)\
**Replies:** 3\
**Last updated:** [December 5, 2020, 9:31am UTC](https://discourse.julialang.org/t/jld2-how-to-load-a-file-from-string/51214 "2020-12-05T09:31:09Z")

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I have series of files saved via JLD2. I want to load them, one by one and do some operations on them. Generally I want to do following: filename = "somefilename.jld" @load filename When I do it I get: julia\> @lo…

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## [Dot operators of hcat failed for CuArray](https://discourse.julialang.org/t/dot-operators-of-hcat-failed-for-cuarray/51174)

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**Author:** [@zqn](https://discourse.julialang.org/u/zqn)\
**Replies:** 2\
**Last updated:** [December 5, 2020, 4:22am UTC](https://discourse.julialang.org/t/dot-operators-of-hcat-failed-for-cuarray/51174 "2020-12-05T04:22:07Z")

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Hi. I’m trying to combining elements with the same locations from two arrays. It’s easy to do that with dot hcat like this. a = randn(5,2) b = randn(5,2) hcat.(a,b) When I store my arrays in GPU as CuArray, it won’t w…

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## [Using Documenter.jl to in GitHub actions](https://discourse.julialang.org/t/using-documenter-jl-to-in-github-actions/51231)

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**Author:** [@ablaom](https://discourse.julialang.org/u/ablaom)\
**Replies:** 5\
**Last updated:** [December 5, 2020, 2:46am UTC](https://discourse.julialang.org/t/using-documenter-jl-to-in-github-actions/51231 "2020-12-05T02:46:54Z")

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The Documenter log seems to suggest that setting push\_preview=true is necessary when generating docs from a git-hub action, as here Is this actually necessary? cc @dilumaluthge

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## [Struct equality seems weird inside Sets](https://discourse.julialang.org/t/struct-equality-seems-weird-inside-sets/51283)

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**Author:** [@bsuwal](https://discourse.julialang.org/u/bsuwal)\
**Replies:** 6\
**Last updated:** [December 5, 2020, 12:52am UTC](https://discourse.julialang.org/t/struct-equality-seems-weird-inside-sets/51283 "2020-12-05T00:52:53Z")

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Can someone help me understand this behavior? So I define a struct. To define what equality means for the struct, I define the == function for the struct, and also a hash() function. Note the println() statements i…

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## [PlutoUI slider value is forced to zero when it is printed in the same MD string with slider](https://discourse.julialang.org/t/plutoui-slider-value-is-forced-to-zero-when-it-is-printed-in-the-same-md-string-with-slider/51261)

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**Author:** [@KajWiik](https://discourse.julialang.org/u/KajWiik)\
**Replies:** 2\
**Last updated:** [December 4, 2020, 8:35pm UTC](https://discourse.julialang.org/t/plutoui-slider-value-is-forced-to-zero-when-it-is-printed-in-the-same-md-string-with-slider/51261 "2020-12-04T20:35:42Z")

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I want to embed a widget and its value in a same markdown string. When the slider position is changed, the value jumps ahead but it is replaced with zero immediately. Is there a better way to accomplish this? It seems th…

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## [Version of \`push!(::Set,v)\` which returns whether \`v\` was already present](https://discourse.julialang.org/t/version-of-push-set-v-which-returns-whether-v-was-already-present/51239)

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**Author:** [@ettersi](https://discourse.julialang.org/u/ettersi)\
**Replies:** 5\
**Last updated:** [December 4, 2020, 5:01pm UTC](https://discourse.julialang.org/t/version-of-push-set-v-which-returns-whether-v-was-already-present/51239 "2020-12-04T17:01:53Z")

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Is there a function which allows me to insert an entry into a set and returns whether the entry was already present? I.e. something like function insert!(s::Set, v) r = v in s push!(s,v) return r end

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