# Latest

**URL:** https://discourse.julialang.org/latest.md?page=1835

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

**Page:** 1836

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## [JuMP for Gurobi 9.0](https://discourse.julialang.org/t/jump-for-gurobi-9-0/33983)

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**Author:** [@Arega\_Getaneh](https://discourse.julialang.org/u/Arega_Getaneh)\
**Replies:** 4\
**Last updated:** [January 30, 2020, 4:55pm UTC](https://discourse.julialang.org/t/jump-for-gurobi-9-0/33983 "2020-01-30T16:55:41Z")

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I want to use the latest version of Gurobi Solver (Gurobi 9.0) since it uses to solve convex and non convex problems unlike the previous versions. On the other hand, JuMP is working for versions up to Gurobi 8.1. Any sug…

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## [Gurobi.GurobiError(10020, “Q matrix is not positive semi-definite (PSD)](https://discourse.julialang.org/t/gurobi-gurobierror-10020-q-matrix-is-not-positive-semi-definite-psd/33995)

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**Author:** [@Arega\_Getaneh](https://discourse.julialang.org/u/Arega_Getaneh)\
**Replies:** 0\
**Last updated:** [January 30, 2020, 6:35pm UTC](https://discourse.julialang.org/t/gurobi-gurobierror-10020-q-matrix-is-not-positive-semi-definite-psd/33995 "2020-01-30T18:35:11Z")

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I have read some solutions for this problem I have using Gurobi. Most answered that Gurobi did not support non convex problems. However, the new version does and that doest work. I wonder if anyone can figure out where m…

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## [PackageCompilerX on Windows](https://discourse.julialang.org/t/packagecompilerx-on-windows/33935)

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**Author:** [@PGS62](https://discourse.julialang.org/u/PGS62)\
**Replies:** 6\
**Last updated:** [January 30, 2020, 5:46pm UTC](https://discourse.julialang.org/t/packagecompilerx-on-windows/33935 "2020-01-30T17:46:26Z")

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I’ve been keeping an eye on @kristoffer.carlsson’s PackageCompilerX and wondering when to try creating a stand-alone executable for some Julia code I have (after previous failures with PackageCompiler). The documentatio…

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## [Element-wise additions behaviour](https://discourse.julialang.org/t/element-wise-additions-behaviour/33984)

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**Author:** [@rpetit](https://discourse.julialang.org/u/rpetit)\
**Replies:** 9\
**Last updated:** [January 30, 2020, 5:04pm UTC](https://discourse.julialang.org/t/element-wise-additions-behaviour/33984 "2020-01-30T17:04:17Z")

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Hi ! I was wondering if someone could explain me the huge gap I noticed in time and memory cost between these two functions. function fwddiff1(γ::Array{T, 2}) where T\<:Real res = zero(γ) for i=1:size(γ)\[1\]-1 …

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## [Big Integers](https://discourse.julialang.org/t/big-integers/33989)

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**Author:** [@ferasawad](https://discourse.julialang.org/u/ferasawad)\
**Replies:** 2\
**Last updated:** [January 30, 2020, 5:22pm UTC](https://discourse.julialang.org/t/big-integers/33989 "2020-01-30T17:22:25Z")

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Hi I am new to Julia. My question is: How can I do arithmetic operations on very big numbers? something like 2^4110 - 3^35 + …

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## [Design of outer constructors](https://discourse.julialang.org/t/design-of-outer-constructors/33937)

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**Author:** [@tomtom](https://discourse.julialang.org/u/tomtom)\
**Replies:** 1\
**Last updated:** [January 30, 2020, 4:59pm UTC](https://discourse.julialang.org/t/design-of-outer-constructors/33937 "2020-01-30T16:59:21Z")

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in StaticArrays @generated function (::Type{SArray{S, T, N}})(x::Tuple) where {S \<: Tuple, T, N} return quote @\_inline\_meta SArray{S, T, N, $(tuple\_prod(S))}(x) end end I see the use of generate…

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## [Saving arrays as .tiff images](https://discourse.julialang.org/t/saving-arrays-as-tiff-images/33985)

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**Author:** [@samantp](https://discourse.julialang.org/u/samantp)\
**Replies:** 1\
**Last updated:** [January 30, 2020, 3:40pm UTC](https://discourse.julialang.org/t/saving-arrays-as-tiff-images/33985 "2020-01-30T15:40:06Z")

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Hi there, I’m quite new to Julia and working in medical image processing. I have a dicom image that I have successfully read in using the DICOM package (it is read as an array, u16, but I can convert this to another type…

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## [Optim.jl: running instructions after each step](https://discourse.julialang.org/t/optim-jl-running-instructions-after-each-step/33969)

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**Author:** [@rpetit](https://discourse.julialang.org/u/rpetit)\
**Replies:** 2\
**Last updated:** [January 30, 2020, 3:12pm UTC](https://discourse.julialang.org/t/optim-jl-running-instructions-after-each-step/33969 "2020-01-30T15:12:28Z")

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Hi ! I would like to use Optim.jl to perform a gradient descent, and for some reason would like after each step to be able to run some instruction, possibly modifying the current iterate. Does anyone know if this is po…

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## [Travis slowdown?](https://discourse.julialang.org/t/travis-slowdown/33977)

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**Author:** [@Tamas\_Papp](https://discourse.julialang.org/u/Tamas_Papp)\
**Replies:** 4\
**Last updated:** [January 30, 2020, 3:03pm UTC](https://discourse.julialang.org/t/travis-slowdown/33977 "2020-01-30T15:03:17Z")

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I am experiencing long (3h+) queue times on Travis CI for recent open source builds, despite status being ostensibly 100%. I am wondering if I missed something, thought I would ask here before contacting them.

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## [Use Sign Function in JuMP NLconstraint](https://discourse.julialang.org/t/use-sign-function-in-jump-nlconstraint/33973)

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**Author:** [@cupcc](https://discourse.julialang.org/u/cupcc)\
**Replies:** 2\
**Last updated:** [January 30, 2020, 2:15pm UTC](https://discourse.julialang.org/t/use-sign-function-in-jump-nlconstraint/33973 "2020-01-30T14:15:06Z")

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I’m currently trying to solve a problem in JuMP that has a nonlinear constraint that has the form y= (other expressions) + constant \* sign(x). This throws an error saying sign is not a recognized function. How do I fix …

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## [Undocumented "fields"?](https://discourse.julialang.org/t/undocumented-fields/33933)

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**Author:** [@tomtom](https://discourse.julialang.org/u/tomtom)\
**Replies:** 4\
**Last updated:** [January 30, 2020, 1:32pm UTC](https://discourse.julialang.org/t/undocumented-fields/33933 "2020-01-30T13:32:53Z")

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in docs, I see the following: eltype\_wrong(::Type{A}) where {A\<:AbstractArray} = A.parameters\[1\] the .parameters, though I can guess what it is, it’s an undocumented “field” of type parameters. I wonder if there’s any o…

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## [Importing Pre-Trained Model in Julia](https://discourse.julialang.org/t/importing-pre-trained-model-in-julia/33952)

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**Author:** [@abianco](https://discourse.julialang.org/u/abianco)\
**Replies:** 2\
**Last updated:** [January 30, 2020, 12:05pm UTC](https://discourse.julialang.org/t/importing-pre-trained-model-in-julia/33952 "2020-01-30T12:05:14Z")

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Is there an effective way to import a pre-trained model (or at least the model specification and weights) in Julia and use it in TensorFlow.jl? If not, are there other ways to load in a pre-trained BLSTM and work with i…

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## [Are there tools to help with testing upper bounds on package dependencies?](https://discourse.julialang.org/t/are-there-tools-to-help-with-testing-upper-bounds-on-package-dependencies/33909)

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**Author:** [@xiaodai](https://discourse.julialang.org/u/xiaodai)\
**Replies:** 3\
**Last updated:** [January 30, 2020, 11:34am UTC](https://discourse.julialang.org/t/are-there-tools-to-help-with-testing-upper-bounds-on-package-dependencies/33909 "2020-01-30T11:34:35Z")

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Following the changes to the package registration processes, it’s good to put upper bounds on packages for auto-approval. However, this causes another minor issue which is that when a package’s dependencies’ semver upgra…

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## [Julia-repl in emacs](https://discourse.julialang.org/t/julia-repl-in-emacs/33769)

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**Author:** [@yzcj105](https://discourse.julialang.org/u/yzcj105)\
**Replies:** 8\
**Last updated:** [January 30, 2020, 11:18am UTC](https://discourse.julialang.org/t/julia-repl-in-emacs/33769 "2020-01-30T11:18:53Z")

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Hello, I used to be a juno user, however, I’d like to switch to emacs to keep everything in the command line. I’m trying to use emacs repl in doom emacs, which is emcas with evil keybindings. The packages I’m using is …

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## [Why parse(UInt8 and parse(Int8 get diffrent type?](https://discourse.julialang.org/t/why-parse-uint8-and-parse-int8-get-diffrent-type/33966)

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**Author:** [@programista](https://discourse.julialang.org/u/programista)\
**Replies:** 6\
**Last updated:** [January 30, 2020, 8:11am UTC](https://discourse.julialang.org/t/why-parse-uint8-and-parse-int8-get-diffrent-type/33966 "2020-01-30T08:11:30Z")

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Julia 0.7 Why parse(UInt8 and parse(Int8 get diffrent type ? julia\> parse(UInt8,"255") 0xff julia\> parse(Int8,"127") 127 Paul

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## [Help wanted with an EXCEPTION\_ACCESS\_VIOLATION](https://discourse.julialang.org/t/help-wanted-with-an-exception-access-violation/33967)

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**Author:** [@seq](https://discourse.julialang.org/u/seq)\
**Replies:** 0\
**Last updated:** [January 30, 2020, 7:55am UTC](https://discourse.julialang.org/t/help-wanted-with-an-exception-access-violation/33967 "2020-01-30T07:55:57Z")

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I have been struggling for many months with a bug whose error message starts like this: Exception: EXCEPTION\_ACCESS\_VIOLATION at 0x2b33f08d -- fmpz\_set at /workspace/srcdir/flint2/fmpz\\set.c:23 I have reported the bug…

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## [Ayush1999's Keras.jl on Julia 1.3.1 precompiling failure](https://discourse.julialang.org/t/ayush1999s-keras-jl-on-julia-1-3-1-precompiling-failure/33951)

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**Author:** [@abianco](https://discourse.julialang.org/u/abianco)\
**Replies:** 10\
**Last updated:** [January 30, 2020, 3:31am UTC](https://discourse.julialang.org/t/ayush1999s-keras-jl-on-julia-1-3-1-precompiling-failure/33951 "2020-01-30T03:31:21Z")

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I see that the package is a bit stale and has not been upgraded to work on Julia 1, however I was able to install it seamlessly in Julia 1.3.1 by executing Pkg.add(Pkg.PackageSpec(url="https://github.com/ayush1999/Keras.…

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## [Unable to evaluate parameters in Juno.@enter debugger](https://discourse.julialang.org/t/unable-to-evaluate-parameters-in-juno-enter-debugger/31680)

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**Author:** [@venuur](https://discourse.julialang.org/u/venuur)\
**Replies:** 15\
**Last updated:** [January 30, 2020, 12:53am UTC](https://discourse.julialang.org/t/unable-to-evaluate-parameters-in-juno-enter-debugger/31680 "2020-01-30T00:53:39Z")

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On Windows 10 with Juno 1.40.0 (I think, downloaded via Julia Pro 1.2), I’m trying to use the Juno debugger via Juno.@enter, but I am unable to evaluate the parameters of my function, unlike in the example. The documenta…

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## [Mayavi mlab usage trouble](https://discourse.julialang.org/t/mayavi-mlab-usage-trouble/33954)

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**Author:** [@sparrowhawk](https://discourse.julialang.org/u/sparrowhawk)\
**Replies:** 0\
**Last updated:** [January 30, 2020, 12:18am UTC](https://discourse.julialang.org/t/mayavi-mlab-usage-trouble/33954 "2020-01-30T00:18:22Z")

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I’m having trouble using mayavi.mlab even though I have been able to install mayavi using Conda. I can do the following mv = pyimport("mayavi") #works but cannot do either of the following mlab = pyimport("mayavi.mla…

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## [Faster way of calculate two-argument ForwardDiff gradient?](https://discourse.julialang.org/t/faster-way-of-calculate-two-argument-forwarddiff-gradient/33948)

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**Author:** [@longemen3000](https://discourse.julialang.org/u/longemen3000)\
**Replies:** 1\
**Last updated:** [January 29, 2020, 8:57pm UTC](https://discourse.julialang.org/t/faster-way-of-calculate-two-argument-forwarddiff-gradient/33948 "2020-01-29T20:57:00Z")

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i have a function f(x1,x2) . sometimes i need dfdx1 , sometimes i need dfdx2, those cases are easy with the existing ForwardDiff API. the problem is when i need the two properties at once. gradient is one way, calling ea…

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## [References in Julia](https://discourse.julialang.org/t/references-in-julia/33946)

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**Author:** [@rvignolo](https://discourse.julialang.org/u/rvignolo)\
**Replies:** 3\
**Last updated:** [January 29, 2020, 8:31pm UTC](https://discourse.julialang.org/t/references-in-julia/33946 "2020-01-29T20:31:39Z")

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Is it possible to change the contents of a vector by means of a pointer? Of course I am aware of the following: julia\> v = zeros(6); julia\> p = v 6-element Array{Float64,1}: 0.0 0.0 0.0 0.0 0.0 0.0 julia\> p\[1\] =…

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## [Julia 1.3.1 cannot automatically install](https://discourse.julialang.org/t/julia-1-3-1-cannot-automatically-install/33869)

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**Author:** [@rvignolo](https://discourse.julialang.org/u/rvignolo)\
**Replies:** 12\
**Last updated:** [January 29, 2020, 8:15pm UTC](https://discourse.julialang.org/t/julia-1-3-1-cannot-automatically-install/33869 "2020-01-29T20:15:00Z")

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Hi! I moved from version 1.2 to 1.3.1 and get the following error when trying to build anything: ERROR: Unable to automatically install 'Expat' from 'C:\\Users\\ramirov\\.julia\\packages\\Expat\_jll\\YXYuQ\\Artifacts.toml' Sta…

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## [Problems using FFTW- SOLVED](https://discourse.julialang.org/t/problems-using-fftw-solved/33930)

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**Author:** [@IgnacioSuarez](https://discourse.julialang.org/u/IgnacioSuarez)\
**Replies:** 10\
**Last updated:** [January 29, 2020, 8:08pm UTC](https://discourse.julialang.org/t/problems-using-fftw-solved/33930 "2020-01-29T20:08:18Z")

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Hi! I am using FFTW in Julia 1.1. I am trying to do the Fourier transform of exp(-0.5\*x^2), whose analytical solution is exactly itself but I obtain a complex array. Does anyone know what I am doing wrong? You can fin…

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## [How to create a random binary array with b bits?](https://discourse.julialang.org/t/how-to-create-a-random-binary-array-with-b-bits/33906)

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**Author:** [@lesshaste](https://discourse.julialang.org/u/lesshaste)\
**Replies:** 15\
**Last updated:** [January 29, 2020, 8:07pm UTC](https://discourse.julialang.org/t/how-to-create-a-random-binary-array-with-b-bits/33906 "2020-01-29T20:07:21Z")

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I would like to make a random binary array with b bits. In fact I will make a lot of them and compute their Hamming distances which I need to be able to do fast. At a low level that means computing XOR between binary arr…

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## [Question - for loop - variable assignments](https://discourse.julialang.org/t/question-for-loop-variable-assignments/33934)

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**Author:** [@o2candoo](https://discourse.julialang.org/u/o2candoo)\
**Replies:** 5\
**Last updated:** [January 29, 2020, 6:01pm UTC](https://discourse.julialang.org/t/question-for-loop-variable-assignments/33934 "2020-01-29T18:01:18Z")

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Hi Community I’m new to Julia (startet today), so if this question does not fit here, let me know. My first idea was to compare Julias speed for simple calculus with other languages i know (its in this particular area …

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## [How to force using Tracker (not Zygote) in Flux 0.10](https://discourse.julialang.org/t/how-to-force-using-tracker-not-zygote-in-flux-0-10/33916)

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**Author:** [@jaynick](https://discourse.julialang.org/u/jaynick)\
**Replies:** 1\
**Last updated:** [January 29, 2020, 2:28pm UTC](https://discourse.julialang.org/t/how-to-force-using-tracker-not-zygote-in-flux-0-10/33916 "2020-01-29T14:28:56Z")

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I want to try this for debugging. In fact one of the Flux example codes does not even run under 0.10.1, error mutating arrays not supported. I tried doing using Tracker before using Flux, however it still gives the erro…

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## [Calling Distributions functions with keywords](https://discourse.julialang.org/t/calling-distributions-functions-with-keywords/33779)

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**Author:** [@mrVeng](https://discourse.julialang.org/u/mrVeng)\
**Replies:** 4\
**Last updated:** [January 29, 2020, 12:15pm UTC](https://discourse.julialang.org/t/calling-distributions-functions-with-keywords/33779 "2020-01-29T12:15:49Z")

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Hi guys, I want to create a (mutable) struct that lets me call functions from the Distributions module in a very generic way, an example container for this looks like this: using Distributions, Parameters import DataSt…

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## [Does defining the type of variables give more speed?](https://discourse.julialang.org/t/does-defining-the-type-of-variables-give-more-speed/33917)

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**Author:** [@Darione](https://discourse.julialang.org/u/Darione)\
**Replies:** 2\
**Last updated:** [January 29, 2020, 9:55am UTC](https://discourse.julialang.org/t/does-defining-the-type-of-variables-give-more-speed/33917 "2020-01-29T09:55:44Z")

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Does defining the type of variables give more speed? If I have a generic Dict () and replace it with a Dict with string keys and array elements as values, should I expect a performance improvement? or, when Julia compil…

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## [How to handle C dependency in packages](https://discourse.julialang.org/t/how-to-handle-c-dependency-in-packages/33643)

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**Author:** [@henry2004y](https://discourse.julialang.org/u/henry2004y)\
**Replies:** 17\
**Last updated:** [January 29, 2020, 9:37am UTC](https://discourse.julialang.org/t/how-to-handle-c-dependency-in-packages/33643 "2020-01-29T09:37:06Z")

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Hi, I am wondering that if I have some C codes in my own package, how should I get the C functions compiled when importing the package? Should I just ship the compiled dynamic libraries \*.so? Are there any examples or g…

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## [Convert between z critical values and confidence levels?](https://discourse.julialang.org/t/convert-between-z-critical-values-and-confidence-levels/33904)

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**Author:** [@Usor](https://discourse.julialang.org/u/Usor)\
**Replies:** 1\
**Last updated:** [January 29, 2020, 5:23am UTC](https://discourse.julialang.org/t/convert-between-z-critical-values-and-confidence-levels/33904 "2020-01-29T05:23:57Z")

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Are there readily available functions to immediately convert between these two?

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