# Latest

**URL:** https://discourse.julialang.org/latest.md?page=1427

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

**Page:** 1428

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## [Course website boilerplate](https://discourse.julialang.org/t/course-website-boilerplate/59134)

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**Author:** [@kevbonham](https://discourse.julialang.org/u/kevbonham)\
**Replies:** 3\
**Last updated:** [April 13, 2021, 10:37am UTC](https://discourse.julialang.org/t/course-website-boilerplate/59134 "2021-04-13T10:37:24Z")

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I’m planning to transition a course website from Documenter to Franklin.jl, which I think will help with a number of things. In particular, I have a bunch of boilerplate that needs to be added to each lesson, assignment,…

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## [Why is work with Q in qr() is so expensive?](https://discourse.julialang.org/t/why-is-work-with-q-in-qr-is-so-expensive/59143)

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**Author:** [@Wei\_Yang](https://discourse.julialang.org/u/Wei_Yang)\
**Replies:** 6\
**Last updated:** [April 13, 2021, 9:33am UTC](https://discourse.julialang.org/t/why-is-work-with-q-in-qr-is-so-expensive/59143 "2021-04-13T09:33:42Z")

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In the picture below, we can see that it is very efficient to generate a random unitary matrix Q using the qr() function in LinearAlgebra. However, if we want to work with the generated Q, it appears to be very expensiv…

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## [Pick rows from array (ndims not known in advance)](https://discourse.julialang.org/t/pick-rows-from-array-ndims-not-known-in-advance/59033)

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**Author:** [@Paul\_Soderlind](https://discourse.julialang.org/u/Paul_Soderlind)\
**Replies:** 5\
**Last updated:** [April 13, 2021, 8:38am UTC](https://discourse.julialang.org/t/pick-rows-from-array-ndims-not-known-in-advance/59033 "2021-04-13T08:38:06Z")

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I want to pick out some rows (in the vector vv, see below) from an array x. The ndims(x) is determined at run time. So far, I use the approach illustrated below. Is there a better way? x1 = \[11 12 13; 21 22 23; …

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## [Creating a JuliaTeX group on github](https://discourse.julialang.org/t/creating-a-juliatex-group-on-github/6288)

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**Author:** [@Azzaare](https://discourse.julialang.org/u/Azzaare)\
**Replies:** 24\
**Last updated:** [April 13, 2021, 8:12am UTC](https://discourse.julialang.org/t/creating-a-juliatex-group-on-github/6288 "2021-04-13T08:12:49Z")

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I am currently writing a module to handle all matters related to bibtex language (bibliography language for LaTeX), such as parsing and conversion to others format (DataBase, other bibliography format, XML, JSON, etc…). …

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## [TeXmacs plugin for Julia](https://discourse.julialang.org/t/texmacs-plugin-for-julia/59164)

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**Author:** [@mgubi](https://discourse.julialang.org/u/mgubi)\
**Replies:** 0\
**Last updated:** [April 13, 2021, 7:39am UTC](https://discourse.julialang.org/t/texmacs-plugin-for-julia/59164 "2021-04-13T07:39:58Z")

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Hi all. At TeXmacs (www.texmacs.org) we have started working on a Julia plugin (see screenshot here https://twitter.com/gnu\_texmacs/status/1381872692312301571). We welcome Julia developers interested in the integration. …

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## [How to find which subtypes are contained in a type](https://discourse.julialang.org/t/how-to-find-which-subtypes-are-contained-in-a-type/59144)

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**Author:** [@SpinolaHours](https://discourse.julialang.org/u/SpinolaHours)\
**Replies:** 2\
**Last updated:** [April 13, 2021, 6:55am UTC](https://discourse.julialang.org/t/how-to-find-which-subtypes-are-contained-in-a-type/59144 "2021-04-13T06:55:49Z")

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Hi there, Difficult to explain issue but an example should be clear: I have a column of type: Vector{Union{Missing, String}} I want to check if String is contained in this type. String \<: Vector{Union{Missing, Strin…

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## [Trouble Understanding Slicing](https://discourse.julialang.org/t/trouble-understanding-slicing/36821)

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**Author:** [@kw\_martin](https://discourse.julialang.org/u/kw_martin)\
**Replies:** 8\
**Last updated:** [April 1, 2020, 3:10pm UTC](https://discourse.julialang.org/t/trouble-understanding-slicing/36821 "2020-04-01T15:10:21Z")

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In the following code, I can’t understand why sum(a\[1,:\],dims=2) gives a different answer then the first row of sum(a\[1:2,:\],dims=2). julia\> a = \[1 2 3 4; 5 6 7 8; 9 10 11 12\]; julia\> sum(a, dims=2) 3×1 Array{Int64,2}:…

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## [StaticArrays, parametric types, type stability](https://discourse.julialang.org/t/staticarrays-parametric-types-type-stability/59095)

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**Author:** [@Philippe\_Maincon1](https://discourse.julialang.org/u/Philippe_Maincon1)\
**Replies:** 7\
**Last updated:** [April 13, 2021, 4:51am UTC](https://discourse.julialang.org/t/staticarrays-parametric-types-type-stability/59095 "2021-04-13T04:51:10Z")

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Here is a little snippet of code using StaticArrays struct JustMyType{N,M} a::Vector{\<:SMatrix{N,M,Float64}} b:: SMatrix{N,M,Float64} end j = JustMyType(\[SMatrix{2,3,Float64}(randn(2,3)) for i=1:4\], …

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## [I don't understand why or how y(:,i) = x creates a function](https://discourse.julialang.org/t/i-dont-understand-why-or-how-y-i-x-creates-a-function/59069)

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**Author:** [@qsi](https://discourse.julialang.org/u/qsi)\
**Replies:** 6\
**Last updated:** [April 13, 2021, 3:50am UTC](https://discourse.julialang.org/t/i-dont-understand-why-or-how-y-i-x-creates-a-function/59069 "2021-04-13T03:50:18Z")

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I’m very new to Julia, but not to coding, having spent the last decade or so mostly in Matlab (and a variety of other languages stretching back to the mists of time…). So I’ve been toying around with some simple projects…

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## [Array size N\*1 Array{type,2} automatically converted to Vector or Array{type, 1}](https://discourse.julialang.org/t/array-size-n-1-array-type-2-automatically-converted-to-vector-or-array-type-1/59140)

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**Author:** [@BMval](https://discourse.julialang.org/u/BMval)\
**Replies:** 4\
**Last updated:** [April 13, 2021, 12:52am UTC](https://discourse.julialang.org/t/array-size-n-1-array-type-2-automatically-converted-to-vector-or-array-type-1/59140 "2021-04-13T00:52:57Z")

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Why array size N\*1 Array{type,2} can’t be automatically converted to Vector or Array{type, 1}. It will be convenient and logical.

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## [Grid creation and donut-like display and color filling](https://discourse.julialang.org/t/grid-creation-and-donut-like-display-and-color-filling/59100)

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**Author:** [@Stephen1](https://discourse.julialang.org/u/Stephen1)\
**Replies:** 8\
**Last updated:** [April 12, 2021, 10:56pm UTC](https://discourse.julialang.org/t/grid-creation-and-donut-like-display-and-color-filling/59100 "2021-04-12T22:56:26Z")

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Hello, Do you know how I could create a grid like this one on Pluto? In this grid, I would like to put numbers in it (not in all the boxes) and draw curves over it. Have a nice day

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## [How to filter columns of a matrix by columns of another matrix](https://discourse.julialang.org/t/how-to-filter-columns-of-a-matrix-by-columns-of-another-matrix/54061)

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**Author:** [@Shazman](https://discourse.julialang.org/u/Shazman)\
**Replies:** 28\
**Last updated:** [April 12, 2021, 10:36pm UTC](https://discourse.julialang.org/t/how-to-filter-columns-of-a-matrix-by-columns-of-another-matrix/54061 "2021-04-12T22:36:58Z")

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Hi I have two matrics in Julia, both matrics are coded by 0,1,2. and I want to exclude the columns of matrix B from columns of matrix A. at the end, I will have new matrix with ( 28960x 41227). how can I do it ? tha…

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## [How to use redirect\_stdout in IJulia (Jupyter notebook)](https://discourse.julialang.org/t/how-to-use-redirect-stdout-in-ijulia-jupyter-notebook/52230)

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**Author:** [@Shuhua](https://discourse.julialang.org/u/Shuhua)\
**Replies:** 1\
**Last updated:** [April 12, 2021, 10:00pm UTC](https://discourse.julialang.org/t/how-to-use-redirect-stdout-in-ijulia-jupyter-notebook/52230 "2021-04-12T22:00:10Z")

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The following redirect\_stdout code works as expected in REPL original\_stdout = stdout (rd, wr) = redirect\_stdout() println("123") println("456") redirect\_stdout(original\_stdout) close(wr) read(rd, String) The output i…

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## [Coverage report problems](https://discourse.julialang.org/t/coverage-report-problems/59133)

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**Author:** [@Ronis\_BR](https://discourse.julialang.org/u/Ronis_BR)\
**Replies:** 0\
**Last updated:** [April 12, 2021, 9:34pm UTC](https://discourse.julialang.org/t/coverage-report-problems/59133 "2021-04-12T21:34:13Z")

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Hi! A looong time ago, I opened this issue about wrong coverage report by Julia: about wrong coverage report by Julia. By that time, passing --inline=no to Julia would fix some problems. However, we needed a patch to…

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## [Can/could type inference & specialisation barriers be created at regions other than function calls?](https://discourse.julialang.org/t/can-could-type-inference-specialisation-barriers-be-created-at-regions-other-than-function-calls/59046)

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**Author:** [@xyz](https://discourse.julialang.org/u/xyz)\
**Replies:** 3\
**Last updated:** [April 12, 2021, 9:19pm UTC](https://discourse.julialang.org/t/can-could-type-inference-specialisation-barriers-be-created-at-regions-other-than-function-calls/59046 "2021-04-12T21:19:38Z")

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Type specialisation happens at function calls, which is why the common function-barrier pattern arises. Speculating a bit: what would be the issue with having some construct that enforces a type-specialisation for a blo…

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## [Best practices / Guidelines for generic methods](https://discourse.julialang.org/t/best-practices-guidelines-for-generic-methods/59098)

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**Author:** [@Uroc327](https://discourse.julialang.org/u/Uroc327)\
**Replies:** 2\
**Last updated:** [April 12, 2021, 9:17pm UTC](https://discourse.julialang.org/t/best-practices-guidelines-for-generic-methods/59098 "2021-04-12T21:17:24Z")

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I wonder if there are any guidelines on the specificity of method arguments. I’m thinking about the trade-offs of making a type very general (e.g., ::Any (or omitted), ::AbstractArray) vs making a type more or less spec…

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## [How do I get screen resolution in Julia?](https://discourse.julialang.org/t/how-do-i-get-screen-resolution-in-julia/59087)

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**Author:** [@Thomas\_Lei](https://discourse.julialang.org/u/Thomas_Lei)\
**Replies:** 2\
**Last updated:** [April 12, 2021, 8:51pm UTC](https://discourse.julialang.org/t/how-do-i-get-screen-resolution-in-julia/59087 "2021-04-12T20:51:35Z")

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I couln’t get displaysize() to return my monitor resolution. I know I can get it with the help of e.g. Gtk.jl, but I’d prefer avoiding using an external package. Is there a way in Julia Base to obtain the screen resolu…

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## [JuMP 0.21.7 released](https://discourse.julialang.org/t/jump-0-21-7-released/59131)

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**Author:** [@odow](https://discourse.julialang.org/u/odow)\
**Replies:** 0\
**Last updated:** [April 12, 2021, 8:42pm UTC](https://discourse.julialang.org/t/jump-0-21-7-released/59131 "2021-04-12T20:42:18Z")

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Dear all, We are happy to announce the release of JuMP 0.21.7. This should be a non-breaking release, please let us know if this isn’t the case by opening a Github issue or joining the developer chatroom. A key feature…

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## [Separate macro for inserting fields in struct in the standard lib](https://discourse.julialang.org/t/separate-macro-for-inserting-fields-in-struct-in-the-standard-lib/59090)

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**Author:** [@Sunny](https://discourse.julialang.org/u/Sunny)\
**Replies:** 1\
**Last updated:** [April 12, 2021, 8:40pm UTC](https://discourse.julialang.org/t/separate-macro-for-inserting-fields-in-struct-in-the-standard-lib/59090 "2021-04-12T20:40:06Z")

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Is there a def macro analogue in julia? # Macro for inserting fields macro def(name, definition) return quote macro $(esc(name))() esc($(Expr(:quote, definition))) end end end @def my\_fields…

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## [Solution concept for "world age" problem occuring with @generated and macros](https://discourse.julialang.org/t/solution-concept-for-world-age-problem-occuring-with-generated-and-macros/57408)

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**Author:** [@rryi](https://discourse.julialang.org/u/rryi)\
**Replies:** 7\
**Last updated:** [April 12, 2021, 7:37pm UTC](https://discourse.julialang.org/t/solution-concept-for-world-age-problem-occuring-with-generated-and-macros/57408 "2021-04-12T19:37:38Z")

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This is not a beginner’s question, it is a question to advanced julia users whether my concept below is a valid and generalizable approach. And if the answers turn out to be positive, it might help others to overcome …

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## [Pluto fails to Compile Plots](https://discourse.julialang.org/t/pluto-fails-to-compile-plots/50886)

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**Author:** [@brett\_knoss](https://discourse.julialang.org/u/brett_knoss)\
**Replies:** 10\
**Last updated:** [April 12, 2021, 8:16pm UTC](https://discourse.julialang.org/t/pluto-fails-to-compile-plots/50886 "2021-04-12T20:16:14Z")

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When I enter using Plots in Pluto.jl it gives the following error. I just updated to the latest version. Before that all it would do is load continually, without an error message. Failed to precompile Plots \[91a5bcdd…

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## [MethodError: no method matching, but the method exists](https://discourse.julialang.org/t/methoderror-no-method-matching-but-the-method-exists/54767)

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**Author:** [@CFS](https://discourse.julialang.org/u/CFS)\
**Replies:** 8\
**Last updated:** [April 12, 2021, 7:30pm UTC](https://discourse.julialang.org/t/methoderror-no-method-matching-but-the-method-exists/54767 "2021-04-12T19:30:30Z")

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I’m getting the following error: ERROR: MethodError: no method matching choose(::Main.Sim.ModelBasedAgent, ::Int64) Closest candidates are: choose(::Main.Sim.ModelFreeAgent, ::Int64) at /home/xxxxx/Projects/simulateag…

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## [ANN: The Documenter Theme Indigo](https://discourse.julialang.org/t/ann-the-documenter-theme-indigo/59127)

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**Author:** [@Roger-luo](https://discourse.julialang.org/u/Roger-luo)\
**Replies:** 0\
**Last updated:** [April 12, 2021, 7:18pm UTC](https://discourse.julialang.org/t/ann-the-documenter-theme-indigo/59127 "2021-04-12T19:18:10Z")

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I’m excited to announce the documenter theme Indigo: GitHub - JuliaDiff/DocThemeIndigo.jl: The Documenter Theme for the ChainRules family of packages. But you can use it too This is originally the theme ChainRules uses,…

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## [How can I use \\= with factorizations?](https://discourse.julialang.org/t/how-can-i-use-with-factorizations/59126)

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**Author:** [@giancarloantonucci](https://discourse.julialang.org/u/giancarloantonucci)\
**Replies:** 7\
**Last updated:** [April 12, 2021, 6:11pm UTC](https://discourse.julialang.org/t/how-can-i-use-with-factorizations/59126 "2021-04-12T18:11:07Z")

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As per title. For example, this works: using LinearAlgebra A = rand(3, 3) b = rand(3) @show b b \\= A @show b b = \[0.09019616214492654, 0.2564457656075061, 0.7120782534101571\] b = \[0.5468125936523385 1.4817879951917017…

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## [Does Julia have an equivalent to MATLAB's linsolve?](https://discourse.julialang.org/t/does-julia-have-an-equivalent-to-matlabs-linsolve/59124)

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**Author:** [@Nash](https://discourse.julialang.org/u/Nash)\
**Replies:** 4\
**Last updated:** [April 12, 2021, 5:47pm UTC](https://discourse.julialang.org/t/does-julia-have-an-equivalent-to-matlabs-linsolve/59124 "2021-04-12T17:47:02Z")

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Does Julia have the equivalent of MATLAB’s linsolve? Link to MATLAB’s function

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## [FFT for Unitful vector](https://discourse.julialang.org/t/fft-for-unitful-vector/59044)

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**Author:** [@Oto\_Brzobohaty](https://discourse.julialang.org/u/Oto_Brzobohaty)\
**Replies:** 10\
**Last updated:** [April 12, 2021, 5:25pm UTC](https://discourse.julialang.org/t/fft-for-unitful-vector/59044 "2021-04-12T17:25:48Z")

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I am trying to use Unitful package to better track units of my physical quantities, and I am a bit confused: Here is example: using Unitful trajectory = trajectory .\* u"m" fft(trajectory) I got the following error: …

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## [ModelingToolkit + IntervalConstraintProgramming: how to build expressions and contractors without "world age" problems or ambiguities](https://discourse.julialang.org/t/modelingtoolkit-intervalconstraintprogramming-how-to-build-expressions-and-contractors-without-world-age-problems-or-ambiguities/59007)

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**Author:** [@cvanaret](https://discourse.julialang.org/u/cvanaret)\
**Replies:** 8\
**Last updated:** [April 12, 2021, 5:23pm UTC](https://discourse.julialang.org/t/modelingtoolkit-intervalconstraintprogramming-how-to-build-expressions-and-contractors-without-world-age-problems-or-ambiguities/59007 "2021-04-12T17:23:30Z")

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Hi, I’m facing a problem of “world age” that my Julia experience doesn’t allow me to comprehend very well. Here is a MWE that uses the ModelingToolkit and IntervalConstraintProgramming packages: using ModelingToolkit u…

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## [\[RFC- ANN\] CachedFunctions.jl](https://discourse.julialang.org/t/rfc-ann-cachedfunctions-jl/34091)

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**Author:** [@longemen3000](https://discourse.julialang.org/u/longemen3000)\
**Replies:** 10\
**Last updated:** [April 12, 2021, 5:10pm UTC](https://discourse.julialang.org/t/rfc-ann-cachedfunctions-jl/34091 "2021-04-12T17:10:14Z")

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Hi, i just want to announce and request for comments about my package: I did this as a possible solution to the calculation of higher order hessians, inspired heavily by this post. the idea is simple: if you have an in…

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## [Meetup Introduction to Differential Equations in Julia](https://discourse.julialang.org/t/meetup-introduction-to-differential-equations-in-julia/58776)

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**Author:** [@schlichtanders](https://discourse.julialang.org/u/schlichtanders)\
**Replies:** 4\
**Last updated:** [April 12, 2021, 4:53pm UTC](https://discourse.julialang.org/t/meetup-introduction-to-differential-equations-in-julia/58776 "2021-04-12T16:53:36Z")

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Hi all, as part of the Julia User Group Munich, every second month there is an introductory course to some Julia topic. The next online meeting is upcoming Monday 12.04.2021. Thanks to Juypter and Binder you can easily…

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## [Specializing broadcasting for a scalar function](https://discourse.julialang.org/t/specializing-broadcasting-for-a-scalar-function/59121)

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**Author:** [@jules](https://discourse.julialang.org/u/jules)\
**Replies:** 5\
**Last updated:** [April 12, 2021, 4:37pm UTC](https://discourse.julialang.org/t/specializing-broadcasting-for-a-scalar-function/59121 "2021-04-12T16:37:13Z")

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Let’s say I have a function function f(a, b) temp = do\_something\_expensive(a) do\_other\_thing(temp, b) end I like writing scalar functions because they don’t obscure the logic with additional loops. But in thi…

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