# Latest

**URL:** https://discourse.julialang.org/latest.md?page=1716

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

**Page:** 1717

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## [Bottleneck when receiving UDP packets?](https://discourse.julialang.org/t/bottleneck-when-receiving-udp-packets/41425)

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**Author:** [@tamasgal](https://discourse.julialang.org/u/tamasgal)\
**Replies:** 24\
**Last updated:** [June 15, 2020, 9:17pm UTC](https://discourse.julialang.org/t/bottleneck-when-receiving-udp-packets/41425 "2020-06-15T21:17:57Z")

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I hope some network experts can help me here, this is probably not-so-Julia-related. My problem is that I am unable to receive more than ~600 UDP packets per second (on my MacBook, on my Xeon it’s ~900/s) however, I am …

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## [Common RL Environment Interface](https://discourse.julialang.org/t/common-rl-environment-interface/41460)

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**Author:** [@zsunberg](https://discourse.julialang.org/u/zsunberg)\
**Replies:** 1\
**Last updated:** [June 15, 2020, 9:12pm UTC](https://discourse.julialang.org/t/common-rl-environment-interface/41460 "2020-06-15T21:12:55Z")

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Hi everyone, after this conversation https://github.com/JuliaReinforcementLearning/ReinforcementLearning.jl/issues/68 we decided to try to create a common reinforcement learning environment interface with very minimal re…

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## [My own Feedforward Neural Network library :-)](https://discourse.julialang.org/t/my-own-feedforward-neural-network-library/37198)

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**Author:** [@sylvaticus](https://discourse.julialang.org/u/sylvaticus)\
**Replies:** 28\
**Last updated:** [June 15, 2020, 9:03pm UTC](https://discourse.julialang.org/t/my-own-feedforward-neural-network-library/37198 "2020-06-15T21:03:36Z")

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I am learning ML, so I created this toy FNN library… Surely is not optimised like in real ML libraries, but it is already pretty flexible and its simplicity may come on hand in implementing custom solutions… using Ra…

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## [Issues with package management](https://discourse.julialang.org/t/issues-with-package-management/41470)

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**Author:** [@Dominic\_Pazzula](https://discourse.julialang.org/u/Dominic_Pazzula)\
**Replies:** 0\
**Last updated:** [June 15, 2020, 8:27pm UTC](https://discourse.julialang.org/t/issues-with-package-management/41470 "2020-06-15T20:27:03Z")

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Still learning Julia… I think I messed up the package repository on my machine and I’m at a loss on how to fix it. I attempted to install a package from github: (@v1.3) pkg\> add https://github.com/tkf/ThreadsX.jl …

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## [Simple documentation question](https://discourse.julialang.org/t/simple-documentation-question/41445)

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**Author:** [@Ferran\_Mazzanti](https://discourse.julialang.org/u/Ferran_Mazzanti)\
**Replies:** 7\
**Last updated:** [June 15, 2020, 6:44pm UTC](https://discourse.julialang.org/t/simple-documentation-question/41445 "2020-06-15T18:44:37Z")

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Hi, this is quite dumb :frowning: I’m trying to document a function that is called CD\_k\_CUDA and I want to document it. I write a doc string like """ CD\_k\_CUDA(x,W) ... """ function CD\_k\_CUDA(x,W) but when i try to…

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## [REPL disappeared](https://discourse.julialang.org/t/repl-disappeared/41440)

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**Author:** [@erlebach](https://discourse.julialang.org/u/erlebach)\
**Replies:** 10\
**Last updated:** [June 15, 2020, 6:37pm UTC](https://discourse.julialang.org/t/repl-disappeared/41440 "2020-06-15T18:37:20Z")

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Hi, After doing some maintenance on my computer, I returned to Atom, and the Repl disappeared! I uninstalled and reinstalled Juno and Julia-client to no avail. Here is an image of what I see. Looking at the far left sid…

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## [Putting Threads.@threads or any macro in an if statement](https://discourse.julialang.org/t/putting-threads-threads-or-any-macro-in-an-if-statement/41406)

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**Author:** [@Michael\_Wang](https://discourse.julialang.org/u/Michael_Wang)\
**Replies:** 9\
**Last updated:** [June 15, 2020, 5:59pm UTC](https://discourse.julialang.org/t/putting-threads-threads-or-any-macro-in-an-if-statement/41406 "2020-06-15T17:59:31Z")

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Is there a way to “turn” macros on and off with a flag/if statement. For example, I have a loop where I calculate forces and in some instances I don’t need to use multiple threads (e.g. avoid overhead). Currently, I ha…

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## [Module not reading properly](https://discourse.julialang.org/t/module-not-reading-properly/41438)

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**Author:** [@erlebach](https://discourse.julialang.org/u/erlebach)\
**Replies:** 3\
**Last updated:** [June 15, 2020, 5:44pm UTC](https://discourse.julialang.org/t/module-not-reading-properly/41438 "2020-06-15T17:44:49Z")

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The use of modules in Julia is painful for me, after using many languages. However, I am persevering. In a file pickle.jl, I have the following code: module Pickle export mypickle, myunpickle using PyCall @pyimport pi…

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## [Understanding Allocations in multithreaded code](https://discourse.julialang.org/t/understanding-allocations-in-multithreaded-code/41442)

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**Author:** [@JonasIsensee](https://discourse.julialang.org/u/JonasIsensee)\
**Replies:** 4\
**Last updated:** [June 15, 2020, 5:37pm UTC](https://discourse.julialang.org/t/understanding-allocations-in-multithreaded-code/41442 "2020-06-15T17:37:12Z")

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Hi, I’m working on speeding up particle simulation using multi-threading and I’ve come across odd allocations in the multi-threaded code that I don’t fully understand and much less know how to get rid of. Here’s a much…

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## [ANN: FortranFiles.jl](https://discourse.julialang.org/t/ann-fortranfiles-jl/3081)

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**Author:** [@traktofon](https://discourse.julialang.org/u/traktofon)\
**Replies:** 5\
**Last updated:** [June 15, 2020, 5:34pm UTC](https://discourse.julialang.org/t/ann-fortranfiles-jl/3081 "2020-06-15T17:34:43Z")

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Dear Julia community, I’d like to announce FortranFiles.jl, a small package for reading and writing Fortran “unformatted” (i.e. binary) files. You might want to use this if you have legacy data produced by Fortran progr…

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## [Course indication for programming in Julia](https://discourse.julialang.org/t/course-indication-for-programming-in-julia/41266)

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**Author:** [@RaquelSantos](https://discourse.julialang.org/u/RaquelSantos)\
**Replies:** 3\
**Last updated:** [June 15, 2020, 5:25pm UTC](https://discourse.julialang.org/t/course-indication-for-programming-in-julia/41266 "2020-06-15T17:25:00Z")

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I am learning to program in Julia and I would like to indicate specific courses for building linear programming models. Thanks!

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## [How to declare a Boolean variable?](https://discourse.julialang.org/t/how-to-declare-a-boolean-variable/41279)

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**Author:** [@RaquelSantos](https://discourse.julialang.org/u/RaquelSantos)\
**Replies:** 4\
**Last updated:** [June 15, 2020, 5:22pm UTC](https://discourse.julialang.org/t/how-to-declare-a-boolean-variable/41279 "2020-06-15T17:22:47Z")

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I need to declare a Boolean variable but I don’t know how to use Bool. How should I do ? I need the variable “i” to assume two values (1, 0) using JuMP, Cbc Model1 = Model(with\_optimizer(Cbc.Optimizer)) @variable(Mode…

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## [Capture all REPL activity into a file?](https://discourse.julialang.org/t/capture-all-repl-activity-into-a-file/41453)

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**Author:** [@reumle](https://discourse.julialang.org/u/reumle)\
**Replies:** 0\
**Last updated:** [June 15, 2020, 4:25pm UTC](https://discourse.julialang.org/t/capture-all-repl-activity-into-a-file/41453 "2020-06-15T16:25:23Z")

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Is there a way ? The available docs (Logging, IO, REPL…) are not immediately clear on this. I am on windows/vscode. Thanks! for reference: Redirecting to Google Groups , same question, but does not solve my problem (…

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## [Revisited : Loading first few lines from data file](https://discourse.julialang.org/t/revisited-loading-first-few-lines-from-data-file/41390)

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**Author:** [@iamsuddhasattwa](https://discourse.julialang.org/u/iamsuddhasattwa)\
**Replies:** 9\
**Last updated:** [June 15, 2020, 4:08pm UTC](https://discourse.julialang.org/t/revisited-loading-first-few-lines-from-data-file/41390 "2020-06-15T16:08:40Z")

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I am revisiting a question I had asked earlier, but none of the solutions work on my 1.1.0 version Julia. I have a data file with 100 rows of data of the form 1 2 3 4 5 6.1 ... I want to load the first few lines, say 1…

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## [Trying to install Jupyter notebooks via JuliaPro](https://discourse.julialang.org/t/trying-to-install-jupyter-notebooks-via-juliapro/41285)

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**Author:** [@Brian\_Ewald](https://discourse.julialang.org/u/Brian_Ewald)\
**Replies:** 1\
**Last updated:** [June 15, 2020, 4:08pm UTC](https://discourse.julialang.org/t/trying-to-install-jupyter-notebooks-via-juliapro/41285 "2020-06-15T16:08:26Z")

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I have some students who are trying to install Jupyter notebooks to be used with JuliaPro, and one of them is running into an installation problem that I can’t figure out. She is using Windows 10, and has no problems ge…

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## [Goto Symbol or '@edit' on remote](https://discourse.julialang.org/t/goto-symbol-or-edit-on-remote/40859)

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**Author:** [@h-spiess](https://discourse.julialang.org/u/h-spiess)\
**Replies:** 1\
**Last updated:** [June 15, 2020, 4:02pm UTC](https://discourse.julialang.org/t/goto-symbol-or-edit-on-remote/40859 "2020-06-15T16:02:57Z")

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Hey, I really like Juno and want to use it to its full potential on a Slurm cluster. I’m able to log into a node by connecting to an external process. Unfortunately, the easier way to connect via ftp-remote-edit doesn’…

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## [With struct do](https://discourse.julialang.org/t/with-struct-do/41341)

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**Author:** [@janrpeters](https://discourse.julialang.org/u/janrpeters)\
**Replies:** 19\
**Last updated:** [June 15, 2020, 3:59pm UTC](https://discourse.julialang.org/t/with-struct-do/41341 "2020-06-15T15:59:02Z")

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A long time ago, I learned Turbo Pascal and there was a contract that allowed: with x do field3 = field1 + field2 end instead of x.field3 = x.field1 + x.field2 where mutable struct compositetype field…

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## [Time to first plot seems to be much alleviated in 1.4. What happend?](https://discourse.julialang.org/t/time-to-first-plot-seems-to-be-much-alleviated-in-1-4-what-happend/37340)

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**Author:** [@xiaodai](https://discourse.julialang.org/u/xiaodai)\
**Replies:** 20\
**Last updated:** [June 15, 2020, 3:16pm UTC](https://discourse.julialang.org/t/time-to-first-plot-seems-to-be-much-alleviated-in-1-4-what-happend/37340 "2020-06-15T15:16:42Z")

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I read somewhere that time to first plot is now much faster. I tried it on Windows 10 Julia v1.4 and plot(1:3) is sub 5 seconds now which is quite acceptable! I wonder what happened, I haven’t been following as closely …

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## [Set index! not defined for WeakRefStrings. SpringArray{String,1}](https://discourse.julialang.org/t/set-index-not-defined-for-weakrefstrings-springarray-string-1/41379)

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**Author:** [@Gp\_Ubit](https://discourse.julialang.org/u/Gp_Ubit)\
**Replies:** 4\
**Last updated:** [June 15, 2020, 2:34pm UTC](https://discourse.julialang.org/t/set-index-not-defined-for-weakrefstrings-springarray-string-1/41379 "2020-06-15T14:34:32Z")

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i wanted to create a loop on a column in my IJulia and I came up with this error. Please what can I do to retify it. Here is my code: for v=1:length(col1) col1\[v\] = Dates.DateTime(col1\[v\], “d-u-y”) end And I got thi…

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## [Global const in struct](https://discourse.julialang.org/t/global-const-in-struct/27718)

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**Author:** [@Tamas\_Papp](https://discourse.julialang.org/u/Tamas_Papp)\
**Replies:** 7\
**Last updated:** [June 15, 2020, 2:05pm UTC](https://discourse.julialang.org/t/global-const-in-struct/27718 "2020-06-15T14:05:19Z")

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In #32407 I saw struct \_GLOBAL\_RNG \<: AbstractRNG global const GLOBAL\_RNG = \_GLOBAL\_RNG.instance end Can someone please explain what this does?

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## [Trying to code a parallel for loop with shared sparse arrays](https://discourse.julialang.org/t/trying-to-code-a-parallel-for-loop-with-shared-sparse-arrays/41265)

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**Author:** [@jbpatzer](https://discourse.julialang.org/u/jbpatzer)\
**Replies:** 18\
**Last updated:** [June 15, 2020, 1:50pm UTC](https://discourse.julialang.org/t/trying-to-code-a-parallel-for-loop-with-shared-sparse-arrays/41265 "2020-06-15T13:50:22Z")

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Having asked here how to code a parallel for loop, and getting a nice answer, I now find myself unable to find anything on how to do it with sparse arrays, as I couldn’t work out how to use sparse arrays with SharedArray…

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## ["Failed to precompile" error on worker processes](https://discourse.julialang.org/t/failed-to-precompile-error-on-worker-processes/40638)

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**Author:** [@BioTurboNick](https://discourse.julialang.org/u/BioTurboNick)\
**Replies:** 17\
**Last updated:** [June 15, 2020, 1:41pm UTC](https://discourse.julialang.org/t/failed-to-precompile-error-on-worker-processes/40638 "2020-06-15T13:41:05Z")

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I’m trying to run my code on multiple processes. It was working before but I updated Atom and it no longer works. I’m getting “failed to precompile” errors when I try to use @everywhere to load a package. Any tips? The …

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## [Garbage collection](https://discourse.julialang.org/t/garbage-collection/41429)

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**Author:** [@Joao\_Barata](https://discourse.julialang.org/u/Joao_Barata)\
**Replies:** 10\
**Last updated:** [June 15, 2020, 12:56pm UTC](https://discourse.julialang.org/t/garbage-collection/41429 "2020-06-15T12:56:46Z")

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Hello, I’m new to Julia. I ran my code and timed it using @time. The results show that gc time is 67.2%. From what I’ve seen in other threads, this is a high figure and is a drag on performance. However, it is unclear t…

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## [Handling unstable true solution issues with the Integrator Interface](https://discourse.julialang.org/t/handling-unstable-true-solution-issues-with-the-integrator-interface/41208)

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**Author:** [@Libbum](https://discourse.julialang.org/u/Libbum)\
**Replies:** 7\
**Last updated:** [June 15, 2020, 12:06pm UTC](https://discourse.julialang.org/t/handling-unstable-true-solution-issues-with-the-integrator-interface/41208 "2020-06-15T12:06:19Z")

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Hi All, Working on a problem that has lead me to the Integrator Interface of DifferentialEquations.jl and have ran into something I can’t seem to work out. My case requires my to solve my ODEProblem on a timescale of d…

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## [Error displaying ParquetFiles.ParquetFile: ArgumentError: reducing over an empty collection is not allowed](https://discourse.julialang.org/t/error-displaying-parquetfiles-parquetfile-argumenterror-reducing-over-an-empty-collection-is-not-allowed/41436)

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**Author:** [@gvarthi](https://discourse.julialang.org/u/gvarthi)\
**Replies:** 0\
**Last updated:** [June 15, 2020, 11:51am UTC](https://discourse.julialang.org/t/error-displaying-parquetfiles-parquetfile-argumenterror-reducing-over-an-empty-collection-is-not-allowed/41436 "2020-06-15T11:51:55Z")

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I am very much new to the Julia Programming language. I am trying to load the parquet file using ParquetFiles.load("part-0001-c000-snappy.parquet"). When I run, I got the following error: \*\*Error displaying ParquetFile…

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## [ERROR: LoadError: ArgumentError: reducing over an empty collection is not allowed](https://discourse.julialang.org/t/error-loaderror-argumenterror-reducing-over-an-empty-collection-is-not-allowed/31758)

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**Author:** [@gohoudanon](https://discourse.julialang.org/u/gohoudanon)\
**Replies:** 7\
**Last updated:** [June 15, 2020, 11:42am UTC](https://discourse.julialang.org/t/error-loaderror-argumenterror-reducing-over-an-empty-collection-is-not-allowed/31758 "2020-06-15T11:42:05Z")

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Hi all, I am not a developer but use Julia for my research as there is an existing nowcasting model. The model works well for the US data (GDP) but comes with ERROR when I replace (manually) the US GDP dates by country…

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## [New package not recognised](https://discourse.julialang.org/t/new-package-not-recognised/41433)

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**Author:** [@compleat](https://discourse.julialang.org/u/compleat)\
**Replies:** 4\
**Last updated:** [June 15, 2020, 11:32am UTC](https://discourse.julialang.org/t/new-package-not-recognised/41433 "2020-06-15T11:32:48Z")

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I added a package but can’t seem to have it be recognised: (v1.2) pkg\> add https://github.com/Staross/JuliaCMAES.git Updating git-repo https://github.com/Staross/JuliaCMAES.git \[ Info: Assigning UUID 51f20bef-1676-51…

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## [Sampling from a list of integers without repetition](https://discourse.julialang.org/t/sampling-from-a-list-of-integers-without-repetition/41395)

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**Author:** [@erlebach](https://discourse.julialang.org/u/erlebach)\
**Replies:** 3\
**Last updated:** [June 15, 2020, 10:53am UTC](https://discourse.julialang.org/t/sampling-from-a-list-of-integers-without-repetition/41395 "2020-06-15T10:53:19Z")

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Given a vector of integers a = collect(1:10) I would like to randomly sample 5 integers with guaranteed non-repetition. As far as I know, b = rand(a, 10) does not guarantee that. This is easily demonstrated via for …

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## [Emacs on Julia - can't copy to/from REPL](https://discourse.julialang.org/t/emacs-on-julia-cant-copy-to-from-repl/41430)

<div class="topic-metadata">

**Author:** [@compleat](https://discourse.julialang.org/u/compleat)\
**Replies:** 3\
**Last updated:** [June 15, 2020, 10:53am UTC](https://discourse.julialang.org/t/emacs-on-julia-cant-copy-to-from-repl/41430 "2020-06-15T10:53:13Z")

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I am not sure if this is just me not understanding or a bug. On my Mac, I use julia-repl and julia-repl-mode and things like ‘ctrl-c’ work to send commands to the REPL but I can’t copy/paste to/from the REPL at all. I …

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## [How do I parse the string "29 February" into a date structure](https://discourse.julialang.org/t/how-do-i-parse-the-string-29-february-into-a-date-structure/41411)

<div class="topic-metadata">

**Author:** [@StevenSiew](https://discourse.julialang.org/u/StevenSiew)\
**Replies:** 3\
**Last updated:** [June 15, 2020, 10:16am UTC](https://discourse.julialang.org/t/how-do-i-parse-the-string-29-february-into-a-date-structure/41411 "2020-06-15T10:16:57Z")

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using Dates julia\> format = Dates.DateFormat("d U") dateformat"d U" julia\> parse(Date,"28 February",format) + Dates.Year(2020-1) 2020-02-28 julia\> parse(Date,"29 February",format) + Dates.Year(2020-1) ERROR: ArgumentEr…

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