# General Usage

**URL:** https://discourse.julialang.org/c/usage/6.md?page=1028

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**Page:** 1029

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## [Problem with DifferentialEquations and overwriting methods](https://discourse.julialang.org/t/problem-with-differentialequations-and-overwriting-methods/417)

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**Author:** [@dawbarton](https://discourse.julialang.org/u/dawbarton)\
**Replies:** 4\
**Last updated:** [September 5, 2017, 6:13pm UTC](https://discourse.julialang.org/t/problem-with-differentialequations-and-overwriting-methods/417 "2017-09-05T18:13:36Z")

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I’ve been trying to integrate some simple parameterized ODEs using the DifferentialEquations.jl package; my normal practice from Matlab has been to define a general function with three inputs (time, state, parameters) an…

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## [No tracking information for current branch](https://discourse.julialang.org/t/no-tracking-information-for-current-branch/5726)

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**Author:** [@yakir12](https://discourse.julialang.org/u/yakir12)\
**Replies:** 2\
**Last updated:** [September 5, 2017, 5:37pm UTC](https://discourse.julialang.org/t/no-tracking-information-for-current-branch/5726 "2017-09-05T17:37:28Z")

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I build a package using PkgTemplates.jl, and everything was fine, until I couldn’t Pkg.update() without the following error: julia\> Pkg.update("BeetleWay") INFO: Updating METADATA... INFO: Computing changes... INFO: No …

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## [BenchmarkTools theory and practice](https://discourse.julialang.org/t/benchmarktools-theory-and-practice/5728)

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**Author:** [@cstjean](https://discourse.julialang.org/u/cstjean)\
**Replies:** 1\
**Last updated:** [September 5, 2017, 3:29pm UTC](https://discourse.julialang.org/t/benchmarktools-theory-and-practice/5728 "2017-09-05T15:29:05Z")

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I understand that BenchmarkTools’ job is a hard one, but is it expected that I frequently see several regressions while rerunning the same benchmark (without code change)? Is there some theory that (under certain assumpt…

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## [Include ffmpeg as a dependency](https://discourse.julialang.org/t/include-ffmpeg-as-a-dependency/5710)

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**Author:** [@yakir12](https://discourse.julialang.org/u/yakir12)\
**Replies:** 4\
**Last updated:** [September 5, 2017, 10:24am UTC](https://discourse.julialang.org/t/include-ffmpeg-as-a-dependency/5710 "2017-09-05T10:24:40Z")

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I’m writing a packages that needs to be able to run(\`ffmpeg ...\`) on all three architectures. I looked into VideoIO’s deps/build.jl file and cowered in fear. Is there any simple way to include a build-dependency on ff…

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## [Using @inline with multiple dispatch](https://discourse.julialang.org/t/using-inline-with-multiple-dispatch/5718)

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**Author:** [@mcovalt](https://discourse.julialang.org/u/mcovalt)\
**Replies:** 4\
**Last updated:** [September 5, 2017, 9:08am UTC](https://discourse.julialang.org/t/using-inline-with-multiple-dispatch/5718 "2017-09-05T09:08:19Z")

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Just curious, what would the behavior of using @inline be when applied to two functions named the same, but operating differently based on types?

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## [Memory allocation issue with iterator type](https://discourse.julialang.org/t/memory-allocation-issue-with-iterator-type/5715)

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**Author:** [@juliohm](https://discourse.julialang.org/u/juliohm)\
**Replies:** 4\
**Last updated:** [September 5, 2017, 12:42am UTC](https://discourse.julialang.org/t/memory-allocation-issue-with-iterator-type/5715 "2017-09-05T00:42:02Z")

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Happy labor day! Anyone around that could help with the following issue? Consider this simple snippet: # DOMAIN abstract type AbstractDomain{T\<:Real,N} end struct RegularGrid{T\<:Real,N} \<: AbstractDomain{T,N} dims:…

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## [Index array using boolean result of a comparison](https://discourse.julialang.org/t/index-array-using-boolean-result-of-a-comparison/5712)

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**Author:** [@ericsfraga](https://discourse.julialang.org/u/ericsfraga)\
**Replies:** 6\
**Last updated:** [September 4, 2017, 2:11pm UTC](https://discourse.julialang.org/t/index-array-using-boolean-result-of-a-comparison/5712 "2017-09-04T14:11:25Z")

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Hello, I am trying to reset the values of a vector (1d array) for any values that are outside a bound. In 0.5, I did the following, for instance: x\[x.\<a\] = a\[x.\<a\] This works if I type it in on the console but fails w…

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## [Blur filter using Parallel Accelerator](https://discourse.julialang.org/t/blur-filter-using-parallel-accelerator/3492)

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**Author:** [@Naelson\_douglas](https://discourse.julialang.org/u/Naelson_douglas)\
**Replies:** 3\
**Last updated:** [September 4, 2017, 2:08pm UTC](https://discourse.julialang.org/t/blur-filter-using-parallel-accelerator/3492 "2017-09-04T14:08:43Z")

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Hello. I’m trying to process an image by using Paralle Accelerator in the following way (it’s the documentation example,actually) runStencil(buffer\_B, Band\_B, 1, oob\_src\_zero) do b, a b\[0,0\] = blur(a) return a, b e…

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## [Type assistance tool for Julia](https://discourse.julialang.org/t/type-assistance-tool-for-julia/5683)

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**Author:** [@linuslagerhjelm](https://discourse.julialang.org/u/linuslagerhjelm)\
**Replies:** 6\
**Last updated:** [September 4, 2017, 2:05pm UTC](https://discourse.julialang.org/t/type-assistance-tool-for-julia/5683 "2017-09-04T14:05:58Z")

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I was wondering if anyone know of a tool that can assist the interaction with the type system? I am fairly new to Julia although I have a lot of experience with other languages. Something that really prevents me from bei…

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## [(x,y) .+= z](https://discourse.julialang.org/t/x-y-z/5696)

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**Author:** [@e3c6](https://discourse.julialang.org/u/e3c6)\
**Replies:** 7\
**Last updated:** [September 4, 2017, 10:45am UTC](https://discourse.julialang.org/t/x-y-z/5696 "2017-09-04T10:45:00Z")

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The following example does not work: x = y = 0. x, y .+= 2. I’d expect this to add 2 to x and y, but instead it throws an error. Is there a reason for this?

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## [Inference failure on tuple](https://discourse.julialang.org/t/inference-failure-on-tuple/5697)

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**Author:** [@gasagna](https://discourse.julialang.org/u/gasagna)\
**Replies:** 10\
**Last updated:** [September 4, 2017, 1:52am UTC](https://discourse.julialang.org/t/inference-failure-on-tuple/5697 "2017-09-04T01:52:08Z")

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It seems like the compiler cannot infer the type of the tuple b in the below MWE, while I think it should. This results in suboptimal performance. I can easily work around this, at the expense of code readability. Worth …

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## [Catching exceptions by type](https://discourse.julialang.org/t/catching-exceptions-by-type/5690)

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**Author:** [@juliohm](https://discourse.julialang.org/u/juliohm)\
**Replies:** 2\
**Last updated:** [September 3, 2017, 3:22pm UTC](https://discourse.julialang.org/t/catching-exceptions-by-type/5690 "2017-09-03T15:22:42Z")

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How to catch exceptions by type? In the documentation I only saw examples catching all types: try # some code catch e # all types if e isa AssertionError # handle exception end end

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## [Volume of the union of a list of overlapping spheres?](https://discourse.julialang.org/t/volume-of-the-union-of-a-list-of-overlapping-spheres/5685)

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**Author:** [@e3c6](https://discourse.julialang.org/u/e3c6)\
**Replies:** 1\
**Last updated:** [September 3, 2017, 12:06am UTC](https://discourse.julialang.org/t/volume-of-the-union-of-a-list-of-overlapping-spheres/5685 "2017-09-03T00:06:27Z")

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Is there a package in Julia (or Python, that I can call from Julia) to compute the volume of the union of a list of overlapping spheres (I specify their position and radius)?

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## [Installation error Flisp for v0.6 on Mac OS 10.12.6](https://discourse.julialang.org/t/installation-error-flisp-for-v0-6-on-mac-os-10-12-6/5686)

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**Author:** [@mopg](https://discourse.julialang.org/u/mopg)\
**Replies:** 2\
**Last updated:** [September 2, 2017, 11:28pm UTC](https://discourse.julialang.org/t/installation-error-flisp-for-v0-6-on-mac-os-10-12-6/5686 "2017-09-02T23:28:50Z")

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I had been using Julia v0.5.2 and just now tried to install Julia v0.6.0 on my Mac OS 10.12.6. In the julia directory I first did make clean, checked out v.0.6.0 and then built it using make. However, I keep getting th…

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## [Is @inbounds really necessary?](https://discourse.julialang.org/t/is-inbounds-really-necessary/5654)

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**Author:** [@antoine-levitt](https://discourse.julialang.org/u/antoine-levitt)\
**Replies:** 14\
**Last updated:** [September 2, 2017, 8:35pm UTC](https://discourse.julialang.org/t/is-inbounds-really-necessary/5654 "2017-09-02T20:35:25Z")

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Writing @inbounds in code is tedious, and ruins the nice alignment of for loops. Is it really necessary? It feels like in simple loops like n = length(x) for i = 1:n x\[i\] \*= 2 end this should be something the compile…

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## [Is ForwardDiff thread safe?](https://discourse.julialang.org/t/is-forwarddiff-thread-safe/5616)

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**Author:** [@vgdev](https://discourse.julialang.org/u/vgdev)\
**Replies:** 3\
**Last updated:** [September 2, 2017, 7:10pm UTC](https://discourse.julialang.org/t/is-forwarddiff-thread-safe/5616 "2017-09-02T19:10:09Z")

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Can I use @threads with ForwardDiff.jl ?

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## [ERROR: function qrfact does not accept keyword arguments](https://discourse.julialang.org/t/error-function-qrfact-does-not-accept-keyword-arguments/5680)

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**Author:** [@mohamed82008](https://discourse.julialang.org/u/mohamed82008)\
**Replies:** 3\
**Last updated:** [September 2, 2017, 2:34pm UTC](https://discourse.julialang.org/t/error-function-qrfact-does-not-accept-keyword-arguments/5680 "2017-09-02T14:34:11Z")

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I get this error when I run: qrfact(rand(50,10), pivot=Val{true}). The docs and help say that I can do that, so what is wrong here?

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## [What wrong i cov() in Julia 5.0?](https://discourse.julialang.org/t/what-wrong-i-cov-in-julia-5-0/2512)

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**Author:** [@programista](https://discourse.julialang.org/u/programista)\
**Replies:** 8\
**Last updated:** [September 2, 2017, 9:21am UTC](https://discourse.julialang.org/t/what-wrong-i-cov-in-julia-5-0/2512 "2017-09-02T09:21:30Z")

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I am calling (Version 0.5.0 (2016-09-19 18:14 UTC) Official http://julialang.org/ releasex86\_64-w64-mingw32) cov according to the documentation: What wrong ? Set D is clear … julia\> cov(D,vardim=1, corrected=false ) W…

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## [Getting data from and to arrays](https://discourse.julialang.org/t/getting-data-from-and-to-arrays/5262)

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**Author:** [@Ferran\_Mazzanti](https://discourse.julialang.org/u/Ferran_Mazzanti)\
**Replies:** 17\
**Last updated:** [September 2, 2017, 8:44am UTC](https://discourse.julialang.org/t/getting-data-from-and-to-arrays/5262 "2017-09-02T08:44:20Z")

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Dear all, a simple question that could however help me a lot with my Monte Carlo codings I’m developping in Julia. The fact is that I need to be able to modify values from an array in several ways. Iagine I have the …

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## [Default constructor for "triangular" types?](https://discourse.julialang.org/t/default-constructor-for-triangular-types/5667)

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**Author:** [@gasagna](https://discourse.julialang.org/u/gasagna)\
**Replies:** 0\
**Last updated:** [August 31, 2017, 10:39pm UTC](https://discourse.julialang.org/t/default-constructor-for-triangular-types/5667 "2017-08-31T22:39:14Z")

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Consider this struct type (defined “triangular” with some abuse of language): julia\> struct Foo{T, N, A\<:AbstractArray{T, N}} \<: AbstractArray{T, N} a::A end It seems that the default constructor does…

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## [Isposdef or isspd?](https://discourse.julialang.org/t/isposdef-or-isspd/5660)

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**Author:** [@MikaelSlevinsky](https://discourse.julialang.org/u/MikaelSlevinsky)\
**Replies:** 1\
**Last updated:** [August 31, 2017, 7:12pm UTC](https://discourse.julialang.org/t/isposdef-or-isspd/5660 "2017-08-31T19:12:27Z")

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The docs say: help?\> isposdef search: isposdef isposdef! isposdef(A) -\> Bool Test whether a matrix is positive definite. Example ≡≡≡≡≡≡≡≡≡ julia\> A = \[1 2; 2 50\] 2×2 Array{Int64,2}: 1 2 2 5…

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## [Reexporting problem types](https://discourse.julialang.org/t/reexporting-problem-types/5650)

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**Author:** [@juliohm](https://discourse.julialang.org/u/juliohm)\
**Replies:** 3\
**Last updated:** [August 31, 2017, 5:09pm UTC](https://discourse.julialang.org/t/reexporting-problem-types/5650 "2017-08-31T17:09:09Z")

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Inspired by the JuliaDiffEq ecosystem and many other awesome Julia frameworks, I am trying to split my package into a Base package that contains the problem definitions and solution specifications. I have finished a firs…

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## [Help with where syntax in Julia v0.6](https://discourse.julialang.org/t/help-with-where-syntax-in-julia-v0-6/4458)

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**Author:** [@juliohm](https://discourse.julialang.org/u/juliohm)\
**Replies:** 36\
**Last updated:** [August 31, 2017, 3:32pm UTC](https://discourse.julialang.org/t/help-with-where-syntax-in-julia-v0-6/4458 "2017-08-31T15:32:38Z")

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I am trying to use the where syntax for the first time, what is wrong with the following usage? abstract type AbstractPoint{N,T} end abstract type AbstractDomain{P} end abstract type AbstractGrid{P} \<: AbstractDomain{P}…

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## [Problem with running command line items](https://discourse.julialang.org/t/problem-with-running-command-line-items/5623)

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**Author:** [@Frank\_Applin](https://discourse.julialang.org/u/Frank_Applin)\
**Replies:** 21\
**Last updated:** [August 31, 2017, 2:45pm UTC](https://discourse.julialang.org/t/problem-with-running-command-line-items/5623 "2017-08-31T14:45:00Z")

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Hi, I’ve read the docs about pipelines, run, readchomp, and the blogs on shelling and pipes, but I can’t figure out how to get these simple commands to work. This is what I would do at a linux command prompt: read -r l…

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## [Problem using kron in Convex](https://discourse.julialang.org/t/problem-using-kron-in-convex/5657)

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**Author:** [@rocknokokoro](https://discourse.julialang.org/u/rocknokokoro)\
**Replies:** 0\
**Last updated:** [August 31, 2017, 12:10pm UTC](https://discourse.julialang.org/t/problem-using-kron-in-convex/5657 "2017-08-31T12:10:47Z")

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Hello I am sort of a beginner with Julia so not sure if I am missusing Convex. I am running a fresh install of Julia 0.52 and cloned the most recent version of Convex. It appears that the object kron returns have diffe…

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## [Julia run using terminal for 1GB dataset showing out of memory error](https://discourse.julialang.org/t/julia-run-using-terminal-for-1gb-dataset-showing-out-of-memory-error/5203)

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**Author:** [@Devi\_Sree](https://discourse.julialang.org/u/Devi_Sree)\
**Replies:** 18\
**Last updated:** [August 31, 2017, 11:26am UTC](https://discourse.julialang.org/t/julia-run-using-terminal-for-1gb-dataset-showing-out-of-memory-error/5203 "2017-08-31T11:26:29Z")

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Can Julia actually support large dataset. My machine has RAM size of 15GB and most of the time when I go for parallel processing with large dataset around 1GB only, it shows out of memory error… If Julia supports, how mu…

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## [Type stable Dict to hold Array{Float64, N} with variable N](https://discourse.julialang.org/t/type-stable-dict-to-hold-array-float64-n-with-variable-n/5647)

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**Author:** [@joaquimg](https://discourse.julialang.org/u/joaquimg)\
**Replies:** 1\
**Last updated:** [August 31, 2017, 4:30am UTC](https://discourse.julialang.org/t/type-stable-dict-to-hold-array-float64-n-with-variable-n/5647 "2017-08-31T04:30:58Z")

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Is there any nice way to make such Dict type stable (where N might vary in different dict entries)? Perhaps annotating when accessing some field (which I always know the size) Or have a dict of Tuple(Vector{Float64},Ve…

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## [Type of type parameters](https://discourse.julialang.org/t/type-of-type-parameters/5646)

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**Author:** [@gasagna](https://discourse.julialang.org/u/gasagna)\
**Replies:** 5\
**Last updated:** [August 30, 2017, 10:39pm UTC](https://discourse.julialang.org/t/type-of-type-parameters/5646 "2017-08-30T22:39:44Z")

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Sometimes I wish I could express that the parameters of a certain parametrised struct must be of a certain type. For example, I would like to have syntax that allows struct ContinuousShift{s::Real} \<: AbstractSymmetry e…

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## [Create documentation locally for unregistered package](https://discourse.julialang.org/t/create-documentation-locally-for-unregistered-package/5630)

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**Author:** [@henrykironde](https://discourse.julialang.org/u/henrykironde)\
**Replies:** 4\
**Last updated:** [August 30, 2017, 9:50pm UTC](https://discourse.julialang.org/t/create-documentation-locally-for-unregistered-package/5630 "2017-08-30T21:50:44Z")

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What could I be doing wrong or still missing in setting up docs . I still cant get the docstrings fetched from source. https://github.com/henrykironde/Retriever.jl/blob/docs/docs/make.jl When I Run Julia make.jl i get t…

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## [Readdlm: ignore\_invalid\_chars option does not exist anymore](https://discourse.julialang.org/t/readdlm-ignore-invalid-chars-option-does-not-exist-anymore/5632)

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**Author:** [@mauro3](https://discourse.julialang.org/u/mauro3)\
**Replies:** 0\
**Last updated:** [August 30, 2017, 3:36pm UTC](https://discourse.julialang.org/t/readdlm-ignore-invalid-chars-option-does-not-exist-anymore/5632 "2017-08-30T15:36:37Z")

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I had a script which using the kw-option ignore\_invalid\_chars (julia 0.4) read a file fine. Now this option does not exist anymore (https://github.com/JuliaLang/julia/pull/16058) and running it without it on my file giv…

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