# General Usage

**URL:** https://discourse.julialang.org/c/usage/6.md?page=869

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

**Page:** 870

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## [Removing a registry](https://discourse.julialang.org/t/removing-a-registry/23727)

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**Author:** [@Andrew\_Gibb](https://discourse.julialang.org/u/Andrew_Gibb)\
**Replies:** 8\
**Last updated:** [May 3, 2019, 9:32pm UTC](https://discourse.julialang.org/t/removing-a-registry/23727 "2019-05-03T21:32:52Z")

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I experimented with creating my own registry. It didn’t work out, because I can’t access our corporate github accounts using the julia package management tools. Fine. It was an experiment. I’ve removed the registry infor…

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## [CSV Parsers dependency problem](https://discourse.julialang.org/t/csv-parsers-dependency-problem/23827)

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**Author:** [@yakir12](https://discourse.julialang.org/u/yakir12)\
**Replies:** 3\
**Last updated:** [May 3, 2019, 8:04pm UTC](https://discourse.julialang.org/t/csv-parsers-dependency-problem/23827 "2019-05-03T20:04:09Z")

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Anyone else experiencing this? julia\> using CSV \[ Info: Precompiling CSV \[336ed68f-0bac-5ca0-87d4-7b16caf5d00b\] ┌ Warning: Package CSV does not have Parsers in its dependencies: │ - If you have CSV checked out for devel…

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## [Behaviour of dispatch with args](https://discourse.julialang.org/t/behaviour-of-dispatch-with-args/23826)

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**Author:** [@hhaensel](https://discourse.julialang.org/u/hhaensel)\
**Replies:** 4\
**Last updated:** [May 3, 2019, 6:52pm UTC](https://discourse.julialang.org/t/behaviour-of-dispatch-with-args/23826 "2019-05-03T18:52:50Z")

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I don’t understand the dispatching of the functions defined below f(a::Int, x::AbstractArray, t = "test") = "array" f(a::Int, x::AbstractRange{\<:Integer}, t) = "range" f(args...) = f(2, args...) f(1:10) and f(2, 1:10) …

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## [Is Julia able to optimize functions that can either return one specific type or \`nothing\`?](https://discourse.julialang.org/t/is-julia-able-to-optimize-functions-that-can-either-return-one-specific-type-or-nothing/23813)

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**Author:** [@ninjaaron](https://discourse.julialang.org/u/ninjaaron)\
**Replies:** 2\
**Last updated:** [May 3, 2019, 3:10pm UTC](https://discourse.julialang.org/t/is-julia-able-to-optimize-functions-that-can-either-return-one-specific-type-or-nothing/23813 "2019-05-03T15:10:02Z")

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I know type stability of functions is a big factor in Julia performance, but I also Julia can also optimize Union{T,Nothing} where T in a lot of cases. Does this extend to functions without declared return types? I know …

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## [Module Loading Case Sensitivity on Windows](https://discourse.julialang.org/t/module-loading-case-sensitivity-on-windows/18523)

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**Author:** [@ReubenHill](https://discourse.julialang.org/u/ReubenHill)\
**Replies:** 10\
**Last updated:** [May 3, 2019, 2:58pm UTC](https://discourse.julialang.org/t/module-loading-case-sensitivity-on-windows/18523 "2019-05-03T14:58:32Z")

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Hi all, I’ve had some frustration when trying to load custom modules on Windows. Could someone clarify exactly what the case sensitivity rules are when trying to load modules, and any differences between file systems wh…

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## [Should we consider BinDeps abandoned?](https://discourse.julialang.org/t/should-we-consider-bindeps-abandoned/23616)

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**Author:** [@lobingera](https://discourse.julialang.org/u/lobingera)\
**Replies:** 8\
**Last updated:** [May 3, 2019, 12:21pm UTC](https://discourse.julialang.org/t/should-we-consider-bindeps-abandoned/23616 "2019-05-03T12:21:51Z")

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The last commit was jan10th, the last merge aug14th 2018, the last release aug15th 2018. Several PRs are pending (incl. \>1.0/1.1 changes preventing \`BinDeps.debug()\` by IanButterworth · Pull Request #395 · JuliaPackaging…

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## [Convert String to DataType](https://discourse.julialang.org/t/convert-string-to-datatype/23803)

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**Author:** [@Eric\_Chen](https://discourse.julialang.org/u/Eric_Chen)\
**Replies:** 6\
**Last updated:** [May 3, 2019, 8:41am UTC](https://discourse.julialang.org/t/convert-string-to-datatype/23803 "2019-05-03T08:41:13Z")

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I have a file that contains a List of what “Algo” I should run Then Julia should read it and Create an instance of the correct “Algo” object: abstract type OptimizationAlgo end struct Linear \<: OptimizationAlgo end str…

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## [Convention: Coding minimal/required API stubs](https://discourse.julialang.org/t/convention-coding-minimal-required-api-stubs/23794)

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**Author:** [@taqtiqa-mark](https://discourse.julialang.org/u/taqtiqa-mark)\
**Replies:** 1\
**Last updated:** [May 3, 2019, 4:42am UTC](https://discourse.julialang.org/t/convention-coding-minimal-required-api-stubs/23794 "2019-05-03T04:42:25Z")

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Hi, Is there a convention around implementing/testing a minimal API for a package? Take StatsBase.jl/src/statsmodels.jl as the example. I have read (misread?) that file as indicating: The minimal API functions that a …

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## [Understanding the allocation behavior on arrays vs scalars](https://discourse.julialang.org/t/understanding-the-allocation-behavior-on-arrays-vs-scalars/23798)

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**Author:** [@jeremiedb](https://discourse.julialang.org/u/jeremiedb)\
**Replies:** 5\
**Last updated:** [May 3, 2019, 3:22am UTC](https://discourse.julialang.org/t/understanding-the-allocation-behavior-on-arrays-vs-scalars/23798 "2019-05-03T03:22:46Z")

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I am confused about the behavior of the allocation, as a significant gain in efficiency seems to be achieved by accumulating values into 2 scalars rather than a vector of 2 values. For the context, the function scans ov…

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## [Help getting matrix combinations that sum to X](https://discourse.julialang.org/t/help-getting-matrix-combinations-that-sum-to-x/23789)

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**Author:** [@tbeason](https://discourse.julialang.org/u/tbeason)\
**Replies:** 3\
**Last updated:** [May 3, 2019, 3:17am UTC](https://discourse.julialang.org/t/help-getting-matrix-combinations-that-sum-to-x/23789 "2019-05-03T03:17:16Z")

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I am trying to find all possible combinations of a matrix where the values sum to some target. It seems rather straightforward but the solution does elude me at the moment. Here is an example matrix. In this example, I’d…

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## [Parallel Random Forest](https://discourse.julialang.org/t/parallel-random-forest/2401)

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**Author:** [@rushirg](https://discourse.julialang.org/u/rushirg)\
**Replies:** 23\
**Last updated:** [May 2, 2019, 10:31pm UTC](https://discourse.julialang.org/t/parallel-random-forest/2401 "2019-05-02T22:31:58Z")

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I am using Random Forest algorithm for classification using build\_forest() and then apply\_forest(). As these operations are running on only one process, how could i parallelize these operations? And how can i generate …

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## [Please stop using \`error\` and \`ErrorException\` in packages (and Base)](https://discourse.julialang.org/t/please-stop-using-error-and-errorexception-in-packages-and-base/12096)

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**Author:** [@oxinabox](https://discourse.julialang.org/u/oxinabox)\
**Replies:** 29\
**Last updated:** [May 2, 2019, 8:34pm UTC](https://discourse.julialang.org/t/please-stop-using-error-and-errorexception-in-packages-and-base/12096 "2019-05-02T20:34:36Z")

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In julia we like to distinguish different things using different types (exceptions are one such thing). In most languages they also like to distinguish different exceptions with different types. In particular in julia …

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## [LapackException(1) while svd but not svdvals](https://discourse.julialang.org/t/lapackexception-1-while-svd-but-not-svdvals/23787)

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**Author:** [@baggepinnen](https://discourse.julialang.org/u/baggepinnen)\
**Replies:** 5\
**Last updated:** [May 2, 2019, 6:59pm UTC](https://discourse.julialang.org/t/lapackexception-1-while-svd-but-not-svdvals/23787 "2019-05-02T18:59:04Z")

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I have a matrix such that julia\> svdvals(AA) 1000-element Array{Float64,1}: 31.962791231191257 31.607090491558335 31.255070632248668 22.374974612534174 ⋮ 22.342788128226456 22.3288133…

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## [Adding special characters to data frame column names](https://discourse.julialang.org/t/adding-special-characters-to-data-frame-column-names/23757)

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**Author:** [@jayce\_ram](https://discourse.julialang.org/u/jayce_ram)\
**Replies:** 4\
**Last updated:** [May 2, 2019, 5:48pm UTC](https://discourse.julialang.org/t/adding-special-characters-to-data-frame-column-names/23757 "2019-05-02T17:48:00Z")

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I would like to create a data frame column name like " Price - $/l " but i can’t find the right syntax… Anyone knows how I could create my dataframe column name that contains special characters like "/’ ? Thanks a lot !…

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## [Double indexing - wondering what's going on](https://discourse.julialang.org/t/double-indexing-wondering-whats-going-on/23777)

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**Author:** [@ezgikurt](https://discourse.julialang.org/u/ezgikurt)\
**Replies:** 2\
**Last updated:** [May 2, 2019, 2:15pm UTC](https://discourse.julialang.org/t/double-indexing-wondering-whats-going-on/23777 "2019-05-02T14:15:29Z")

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Hi, I came upon this issue in one of my functions and wondering what’s going on in the background. I am trying to reassign some elements in an array, but this does not work when I use double indexing (see below for a sim…

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## [Implementing a pointwise arithmetic on functions](https://discourse.julialang.org/t/implementing-a-pointwise-arithmetic-on-functions/23769)

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**Author:** [@kkmann](https://discourse.julialang.org/u/kkmann)\
**Replies:** 7\
**Last updated:** [May 2, 2019, 12:54pm UTC](https://discourse.julialang.org/t/implementing-a-pointwise-arithmetic-on-functions/23769 "2019-05-02T12:54:54Z")

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Hey, I just came across a problem that I am sure can be solved elegantly in Julia but I am lacking a good starting angle. Assume that I have a collection of functors (callable types) of the form struct Functor f::fun…

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## [Subtypes() function. Why is it so slow? Why return a Vector of Any?](https://discourse.julialang.org/t/subtypes-function-why-is-it-so-slow-why-return-a-vector-of-any/17699)

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**Author:** [@Raf](https://discourse.julialang.org/u/Raf)\
**Replies:** 14\
**Last updated:** [May 2, 2019, 1:07pm UTC](https://discourse.julialang.org/t/subtypes-function-why-is-it-so-slow-why-return-a-vector-of-any/17699 "2019-05-02T13:07:55Z")

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julia\> @btime subtypes(Integer) 11.106 ms (3959 allocations: 1.71 MiB) 3-element Array{Any,1}: Bool Signed Unsigned It seems to strange to return an unstable return type. And why does it do anything at runtim…

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## [Float set\_printoptions](https://discourse.julialang.org/t/float-set-printoptions/23775)

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**Author:** [@mfleader](https://discourse.julialang.org/u/mfleader)\
**Replies:** 0\
**Last updated:** [May 2, 2019, 1:07pm UTC](https://discourse.julialang.org/t/float-set-printoptions/23775 "2019-05-02T13:07:05Z")

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Using this function in IPynb is helpful for interactive coding with arrays of floats. numpy.set\_printoptions(precision = 3) I have been unable to figure out what the Julia or IJulia alternative is. My current fix is to…

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## [Revise.jl not working for jupyter server on LSF based cluster](https://discourse.julialang.org/t/revise-jl-not-working-for-jupyter-server-on-lsf-based-cluster/23768)

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**Author:** [@fgerick](https://discourse.julialang.org/u/fgerick)\
**Replies:** 6\
**Last updated:** [May 2, 2019, 12:15pm UTC](https://discourse.julialang.org/t/revise-jl-not-working-for-jupyter-server-on-lsf-based-cluster/23768 "2019-05-02T12:15:03Z")

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Hi, I’m regularly running a notebook server on an LSF based linux cluster. However, I can’t seem to get Revise to work. Any code changes have no impact on the running session, even with manually running revise(). Is thi…

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## [How do I call a shell command containing both single and double quotes](https://discourse.julialang.org/t/how-do-i-call-a-shell-command-containing-both-single-and-double-quotes/23761)

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**Author:** [@PeterB](https://discourse.julialang.org/u/PeterB)\
**Replies:** 0\
**Last updated:** [May 2, 2019, 2:43am UTC](https://discourse.julialang.org/t/how-do-i-call-a-shell-command-containing-both-single-and-double-quotes/23761 "2019-05-02T02:43:29Z")

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This Julia command works: run(\`/Applications/MATLAB\_R2018b.app/bin/matlab -nodisplay -nojvm -r "findalpha('file1'); exit"\`)\` However I want to build a general string between the backquote, so that both the Matlab path,…

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## [Sockets.PipeServer serves named sockets not named pipes](https://discourse.julialang.org/t/sockets-pipeserver-serves-named-sockets-not-named-pipes/23759)

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**Author:** [@jdjohnston](https://discourse.julialang.org/u/jdjohnston)\
**Replies:** 0\
**Last updated:** [May 2, 2019, 1:52am UTC](https://discourse.julialang.org/t/sockets-pipeserver-serves-named-sockets-not-named-pipes/23759 "2019-05-02T01:52:22Z")

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Sockets.PipeServer allows connections with AF\_UNIX/AF\_LOCAL connections (named sockets) not named pipes AKA FIFOs. These are completely different gizmos, at least on Linux. Other than being named and providing communicat…

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## [Eval cannot be used in a generated function](https://discourse.julialang.org/t/eval-cannot-be-used-in-a-generated-function/23630)

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**Author:** [@schlichtanders](https://discourse.julialang.org/u/schlichtanders)\
**Replies:** 15\
**Last updated:** [May 2, 2019, 12:16am UTC](https://discourse.julialang.org/t/eval-cannot-be-used-in-a-generated-function/23630 "2019-05-02T00:16:59Z")

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I would like to create adhoc a new type inside a generated function by eval some text like @eval begin struct MyType end end but this gives the error eval cannot be used in a generated function It would really simp…

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## [Cloud computing environment that supports Julia](https://discourse.julialang.org/t/cloud-computing-environment-that-supports-julia/23749)

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**Author:** [@Mr.Robot](https://discourse.julialang.org/u/Mr.Robot)\
**Replies:** 5\
**Last updated:** [May 1, 2019, 11:11pm UTC](https://discourse.julialang.org/t/cloud-computing-environment-that-supports-julia/23749 "2019-05-01T23:11:40Z")

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Problem I am trying to see the how much GPU could help to accelerate my code by ArrayFire.jl. However, I currently do not have access to GPU on my machine. I have tried two different ways Try to use the integrated Inte…

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## [Pkg: \`CodeTracking\` not found](https://discourse.julialang.org/t/pkg-codetracking-not-found/23739)

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**Author:** [@ExpandingMan](https://discourse.julialang.org/u/ExpandingMan)\
**Replies:** 3\
**Last updated:** [May 1, 2019, 5:39pm UTC](https://discourse.julialang.org/t/pkg-codetracking-not-found/23739 "2019-05-01T17:39:18Z")

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I inadvertently made some manual changes to my Manifest.jl and now every time I use \]status I get the following error ERROR: KeyError: key "CodeTracking" not found Stacktrace: \[1\] getindex(::Dict{String,Any}, ::String)…

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## [Are some packages "official", in some sense?](https://discourse.julialang.org/t/are-some-packages-official-in-some-sense/23724)

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**Author:** [@PeterB](https://discourse.julialang.org/u/PeterB)\
**Replies:** 5\
**Last updated:** [May 1, 2019, 4:57pm UTC](https://discourse.julialang.org/t/are-some-packages-official-in-some-sense/23724 "2019-05-01T16:57:32Z")

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I am delivering Julia code to a customer. Can I be “sure” that some packages will be available for them to download by simply running a little program I give them, which just runs the appropriate Pkg.add() commands? To …

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## [Remove duplicated rows](https://discourse.julialang.org/t/remove-duplicated-rows/23734)

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**Author:** [@alphasig329](https://discourse.julialang.org/u/alphasig329)\
**Replies:** 2\
**Last updated:** [May 1, 2019, 4:35pm UTC](https://discourse.julialang.org/t/remove-duplicated-rows/23734 "2019-05-01T16:35:52Z")

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Is there a function like R’s unique with JuliaDB to remove duplicated rows?

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## [Translate fortran to julia](https://discourse.julialang.org/t/translate-fortran-to-julia/23624)

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**Author:** [@jw3126](https://discourse.julialang.org/u/jw3126)\
**Replies:** 26\
**Last updated:** [May 1, 2019, 3:58pm UTC](https://discourse.julialang.org/t/translate-fortran-to-julia/23624 "2019-05-01T15:58:23Z")

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I have a Fortran code and would prefer if it was a julia code instead :slight\_smile: . The code heavily uses common blocks. Is there a semi automatic way to translate this into (non idiomatic, but executable) julia?

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## [Precompile all the functions within a function](https://discourse.julialang.org/t/precompile-all-the-functions-within-a-function/23695)

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**Author:** [@vitreo12](https://discourse.julialang.org/u/vitreo12)\
**Replies:** 2\
**Last updated:** [May 1, 2019, 2:42pm UTC](https://discourse.julialang.org/t/precompile-all-the-functions-within-a-function/23695 "2019-05-01T14:42:35Z")

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Hello everyone, I was playing around with the precompile function, and I noticed that it does not precompile all the functions that are called within the precompiled function. For example, consider: @time a = 100 #make…

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## [Problem with folder: logs/repl\_history.jl](https://discourse.julialang.org/t/problem-with-folder-logs-repl-history-jl/23697)

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**Author:** [@Afonso\_Dias](https://discourse.julialang.org/u/Afonso_Dias)\
**Replies:** 2\
**Last updated:** [May 1, 2019, 2:08pm UTC](https://discourse.julialang.org/t/problem-with-folder-logs-repl-history-jl/23697 "2019-05-01T14:08:43Z")

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Hi, I am working with Ubuntu/Julia and, when I open julia, this problem appear: ERROR: SystemError: opening file /home/user/.julia/logs/repl\_history.jl: Permission denied Stacktrace: \*\* \[1\] #systemerror#39(::Nothing,…

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## [How to use the iterator with strings with NamedTuple?](https://discourse.julialang.org/t/how-to-use-the-iterator-with-strings-with-namedtuple/23730)

<div class="topic-metadata">

**Author:** [@programista](https://discourse.julialang.org/u/programista)\
**Replies:** 7\
**Last updated:** [May 1, 2019, 12:30pm UTC](https://discourse.julialang.org/t/how-to-use-the-iterator-with-strings-with-namedtuple/23730 "2019-05-01T12:30:48Z")

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I have NamedTuple with many Arrays kolumny julia\> kolumny.M1 1020-element Array{Any,1}: 2.0 … 1.0 Is OK ,is working But my iterator B is a array of string \`\`\`julia\> B 5-element Array{String,1}: "M0" "M1" "M2"…

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