# Internals & Design

**URL:** https://discourse.julialang.org/c/dev/5.md?no_subcategories=false&page=22

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**Page:** 23

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## [The default alignment of markdown table should be left-aligned?](https://discourse.julialang.org/t/the-default-alignment-of-markdown-table-should-be-left-aligned/85344)

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**Author:** [@hyrodium](https://discourse.julialang.org/u/hyrodium)\
**Replies:** 0\
**Last updated:** [August 5, 2022, 1:03pm UTC](https://discourse.julialang.org/t/the-default-alignment-of-markdown-table-should-be-left-aligned/85344 "2022-08-05T13:03:40Z")

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Julia’s default tables are right-aligned (See documentation), but many other markdown parsers default to left-aligned (e.g. GitHub markdown). I have made some PRs to some docs (PlotDocs.jl, Images.jl) because left-align…

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## [AbstractVector vs AbstractRange: length vs size -- which is fundamental?](https://discourse.julialang.org/t/abstractvector-vs-abstractrange-length-vs-size-which-is-fundamental/64689)

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**Author:** [@jishnub](https://discourse.julialang.org/u/jishnub)\
**Replies:** 3\
**Last updated:** [July 28, 2022, 9:01pm UTC](https://discourse.julialang.org/t/abstractvector-vs-abstractrange-length-vs-size-which-is-fundamental/64689 "2022-07-28T21:01:17Z")

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It appears that julia master has changed a behavior from previous versions, and now size for an AbstractRange is defined as (length(r),) instead of the previous behavior where length was defined as prod(size(r)). This ma…

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## [Should Julia be a systems language?](https://discourse.julialang.org/t/should-julia-be-a-systems-language/84861)

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**Author:** [@kodintent](https://discourse.julialang.org/u/kodintent)\
**Replies:** 9\
**Last updated:** [July 28, 2022, 1:05am UTC](https://discourse.julialang.org/t/should-julia-be-a-systems-language/84861 "2022-07-28T01:05:30Z")

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This is a rather speculative post about Julia being used for building systems from scratch, as an alternative to ‘the C way’. Recently i spent some time learning Rust, as it infers it can be systems programming ‘for all…

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## [Which of \`::\` and \`where\` should take precedence?](https://discourse.julialang.org/t/which-of-and-where-should-take-precedence/84807)

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**Author:** [@shaowei](https://discourse.julialang.org/u/shaowei)\
**Replies:** 4\
**Last updated:** [July 27, 2022, 5:11am UTC](https://discourse.julialang.org/t/which-of-and-where-should-take-precedence/84807 "2022-07-27T05:11:39Z")

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Currently (Julia v1.7), where takes precedence over ::. For example: julia\> :(f(x::T where T \<: Integer)) :(f(x::(T where T \<: Integer))) However, this means that the return type annotation will not play nice with para…

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## [Why are scalars iterable when broadcasting would still work fine if they weren't?](https://discourse.julialang.org/t/why-are-scalars-iterable-when-broadcasting-would-still-work-fine-if-they-werent/84785)

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**Author:** [@Jollywatt](https://discourse.julialang.org/u/Jollywatt)\
**Replies:** 2\
**Last updated:** [July 26, 2022, 3:24am UTC](https://discourse.julialang.org/t/why-are-scalars-iterable-when-broadcasting-would-still-work-fine-if-they-werent/84785 "2022-07-26T03:24:11Z")

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This is a soft-question about an aspect of Julia’s design and history. It’s a well-discussed point that scalars are iterable, in the sense that: julia\> 42\[1\], 42\[\], size(42), length(42) (42, 42, (), 1) julia\> collect(…

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## [What is harder about saving a Julia session via the REPL whenever?](https://discourse.julialang.org/t/what-is-harder-about-saving-a-julia-session-via-the-repl-whenever/82897)

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**Author:** [@Benny](https://discourse.julialang.org/u/Benny)\
**Replies:** 10\
**Last updated:** [July 26, 2022, 3:05am UTC](https://discourse.julialang.org/t/what-is-harder-about-saving-a-julia-session-via-the-repl-whenever/82897 "2022-07-26T03:05:13Z")

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I’m learning PackageCompiler.jl, and I’m wondering why creating a sysimage requires an input of packages, the project/environment, and precompile scripts. I do appreciate the paper trail, but couldn’t a sysimage be creat…

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## [Push! to reshape-d vector unshares data with parent array](https://discourse.julialang.org/t/push-to-reshape-d-vector-unshares-data-with-parent-array/84664)

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**Author:** [@Benny](https://discourse.julialang.org/u/Benny)\
**Replies:** 9\
**Last updated:** [July 24, 2022, 12:45pm UTC](https://discourse.julialang.org/t/push-to-reshape-d-vector-unshares-data-with-parent-array/84664 "2022-07-24T12:45:57Z")

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Minimal example below. Pushing to a reshaped vector y seems to allocate a copy of the original matrix x so that they no longer share data, but it’s strange because it doesn’t seem to reassign y, which would print a warni…

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## [Binary Caching and Pre-compilation .. again](https://discourse.julialang.org/t/binary-caching-and-pre-compilation-again/19589)

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**Author:** [@TsurHerman](https://discourse.julialang.org/u/TsurHerman)\
**Replies:** 7\
**Last updated:** [July 22, 2022, 3:31am UTC](https://discourse.julialang.org/t/binary-caching-and-pre-compilation-again/19589 "2022-07-22T03:31:35Z")

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I want to present here again and perhaps more clearly, the concept of context dispatch , or more precisely resolving multiple dispatch based on some context. I believe this can contribute to precompilation and load time…

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## [Is there anything users can do to help move Apple Silicon support from Tier 3 to Tier 1?](https://discourse.julialang.org/t/is-there-anything-users-can-do-to-help-move-apple-silicon-support-from-tier-3-to-tier-1/72739)

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**Author:** [@CameronBieganek](https://discourse.julialang.org/u/CameronBieganek)\
**Replies:** 33\
**Last updated:** [July 19, 2022, 10:17pm UTC](https://discourse.julialang.org/t/is-there-anything-users-can-do-to-help-move-apple-silicon-support-from-tier-3-to-tier-1/72739 "2022-07-19T22:17:34Z")

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Is there anything users can do to help move Apple Silicon support from Tier 3 to Tier 1? Given that most new Mac machines now have an M1 chip, it seems like there will be more and more Julia programmers wanting to use a …

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## [Dealing with external libraries that don't restore old signal handlers](https://discourse.julialang.org/t/dealing-with-external-libraries-that-dont-restore-old-signal-handlers/84343)

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**Author:** [@sobhan](https://discourse.julialang.org/u/sobhan)\
**Replies:** 7\
**Last updated:** [July 17, 2022, 5:54pm UTC](https://discourse.julialang.org/t/dealing-with-external-libraries-that-dont-restore-old-signal-handlers/84343 "2022-07-17T17:54:03Z")

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TLDR: if the code is segfaulting outside Ccalls AFTER Ccalls in threaded GC, it might be that the C library has loaded a custom signal handler and is competing with julia’s handler. The solution is something like """ s…

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## [The role of femtolisp in Julia?](https://discourse.julialang.org/t/the-role-of-femtolisp-in-julia/1902)

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**Author:** [@abhi18av](https://discourse.julialang.org/u/abhi18av)\
**Replies:** 40\
**Last updated:** [July 11, 2022, 8:25pm UTC](https://discourse.julialang.org/t/the-role-of-femtolisp-in-julia/1902 "2022-07-11T20:25:44Z")

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Hii Julians, I was wondering about the exact usage of femtolisp in julia. I’ve Googled around but the nothing exact came up, though there were some references in the old archives. I know that the julia-parser has a nat…

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## [Why is it possible to change the values of a row of a given matrix with a new matrix?](https://discourse.julialang.org/t/why-is-it-possible-to-change-the-values-of-a-row-of-a-given-matrix-with-a-new-matrix/84322)

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**Author:** [@Shayan](https://discourse.julialang.org/u/Shayan)\
**Replies:** 2\
**Last updated:** [July 16, 2022, 7:25pm UTC](https://discourse.julialang.org/t/why-is-it-possible-to-change-the-values-of-a-row-of-a-given-matrix-with-a-new-matrix/84322 "2022-07-16T19:25:34Z")

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I tried to pick an exact and explicit title for this question but failed. So I guess you must read my entire question to understand the issue. In Julia, we can define a random 2\*5 Matrix using rand(2,5): julia\> a = ran…

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## [Standard interface definitions for Julia?](https://discourse.julialang.org/t/standard-interface-definitions-for-julia/82181)

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**Author:** [@ufechner7](https://discourse.julialang.org/u/ufechner7)\
**Replies:** 12\
**Last updated:** [July 16, 2022, 6:43am UTC](https://discourse.julialang.org/t/standard-interface-definitions-for-julia/82181 "2022-07-16T06:43:39Z")

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I think a standard way to define interfaces in Julia, combined with a standard way to test if type satisfies all interfaces that are defined on it would be useful to improve the quality and reliability of the Julia packa…

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## [How does the compiler know not to constant-fold methods like rand?](https://discourse.julialang.org/t/how-does-the-compiler-know-not-to-constant-fold-methods-like-rand/84092)

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**Author:** [@Benny](https://discourse.julialang.org/u/Benny)\
**Replies:** 2\
**Last updated:** [July 12, 2022, 10:15am UTC](https://discourse.julialang.org/t/how-does-the-compiler-know-not-to-constant-fold-methods-like-rand/84092 "2022-07-12T10:15:53Z")

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It seems like for the most part, the compiler tries very hard to compute constant expressions at compile-time, though I’ve seen it give up on loops. But there are situations where it sensibly doesn’t even try, like rand(…

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## [Embedding Julia in the Java Virtual Machine](https://discourse.julialang.org/t/embedding-julia-in-the-java-virtual-machine/51444)

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**Author:** [@mkitti](https://discourse.julialang.org/u/mkitti)\
**Replies:** 11\
**Last updated:** [October 5, 2021, 1:55pm UTC](https://discourse.julialang.org/t/embedding-julia-in-the-java-virtual-machine/51444 "2021-10-05T13:55:06Z")

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Is it easier to embed Julia into the Java Virtual Machine (JVM) or easier to embed the JVM into Julia? Embedding the JVM into Julia I’ve been working with @avik on JavaCall.jl for the better part of this year. To make …

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## [\[Parser\] Allow comma between struct fields and at the end of exported object list](https://discourse.julialang.org/t/parser-allow-comma-between-struct-fields-and-at-the-end-of-exported-object-list/84049)

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**Author:** [@sylvaticus](https://discourse.julialang.org/u/sylvaticus)\
**Replies:** 0\
**Last updated:** [July 11, 2022, 1:26pm UTC](https://discourse.julialang.org/t/parser-allow-comma-between-struct-fields-and-at-the-end-of-exported-object-list/84049 "2022-07-11T13:26:52Z")

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I have a cup of minor issues that bother me from time to time. The first one is that it is currently an error to have a comma between struct fields, e.g. this is an error: struct Foo a::Int64, b::Int64 end The…

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## [OffsetArrays, inbounds, and confusion](https://discourse.julialang.org/t/offsetarrays-inbounds-and-confusion/81295)

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**Author:** [@fft](https://discourse.julialang.org/u/fft)\
**Replies:** 53\
**Last updated:** [July 10, 2022, 7:27am UTC](https://discourse.julialang.org/t/offsetarrays-inbounds-and-confusion/81295 "2022-07-10T07:27:50Z")

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There has been quite a bit of activity around the Yuri Vishnevsky article. Thought I would but some of my thoughts here as someone who is fairly new to Julia and heavily uses C++ and python professionally. As others hav…

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## [Lacking documentation about non-types as type parameters](https://discourse.julialang.org/t/lacking-documentation-about-non-types-as-type-parameters/83893)

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**Author:** [@yakir12](https://discourse.julialang.org/u/yakir12)\
**Replies:** 0\
**Last updated:** [July 7, 2022, 1:31pm UTC](https://discourse.julialang.org/t/lacking-documentation-about-non-types-as-type-parameters/83893 "2022-07-07T13:31:24Z")

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Type parameters can be non-types that are isbits (see 3rd bullet point in Types · The Julia Language): julia\> struct A{T} end julia\> A{1.2} A{1.2} julia\> A{'a'} A{'a'} julia\> A{π} A{π} julia\> A{1//2} A{1//2} julia\> …

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## [Does \`AbstractArray\` itself need to support indexing beyond 1-based?](https://discourse.julialang.org/t/does-abstractarray-itself-need-to-support-indexing-beyond-1-based/83324)

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**Author:** [@Benny](https://discourse.julialang.org/u/Benny)\
**Replies:** 15\
**Last updated:** [July 5, 2022, 11:48pm UTC](https://discourse.julialang.org/t/does-abstractarray-itself-need-to-support-indexing-beyond-1-based/83324 "2022-07-05T23:48:24Z")

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I was thinking about the thread (partially) about the incompatibility of some existing AbstractArray methods with OffsetArrays, and it got me wondering why AbstractArray was extended beyond 1-based indexing. Sticking to …

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## [How to iterate all block statements in IRCode?](https://discourse.julialang.org/t/how-to-iterate-all-block-statements-in-ircode/83701)

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**Author:** [@dfdx](https://discourse.julialang.org/u/dfdx)\
**Replies:** 5\
**Last updated:** [July 4, 2022, 6:29am UTC](https://discourse.julialang.org/t/how-to-iterate-all-block-statements-in-ircode/83701 "2022-07-04T06:29:27Z")

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Say, I have an instance of IRCode like this: 7 1 ─ %1 = Main.bar(\_2)::Tuple{Float64, Float64} │ │ %2 = Base.indexed\_iterate(%1, 1)::PartialStruct(Tuple{Float64, Int64}, Any\[Float…

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## [Is \* a ternary/quarternary operator in 1.7+, or am I missing something that was there before?](https://discourse.julialang.org/t/is-a-ternary-quarternary-operator-in-1-7-or-am-i-missing-something-that-was-there-before/83714)

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**Author:** [@Benny](https://discourse.julialang.org/u/Benny)\
**Replies:** 4\
**Last updated:** [July 4, 2022, 2:10am UTC](https://discourse.julialang.org/t/is-a-ternary-quarternary-operator-in-1-7-or-am-i-missing-something-that-was-there-before/83714 "2022-07-04T02:10:34Z")

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So I noticed this bit in matmul.jl # Three-argument \* """ \*(A, B::AbstractMatrix, C) A \* B \* C \* D Chained multiplication of 3 or 4 matrices is done in the most efficient sequence, based on the sizes of the arra…

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## [Benchmarking Dict against C++ std::unordered\_map](https://discourse.julialang.org/t/benchmarking-dict-against-c-std-unordered-map/83669)

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**Author:** [@greatpet](https://discourse.julialang.org/u/greatpet)\
**Replies:** 6\
**Last updated:** [July 3, 2022, 11:27pm UTC](https://discourse.julialang.org/t/benchmarking-dict-against-c-std-unordered-map/83669 "2022-07-03T23:27:12Z")

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I benchmarked Julia’s dictionary insertion and deletion with the following code, function test\_julia\_dict(n::Int64) m = Dict{Int, Int}() for i = 1:n m\[5\*i\] = i end for i = 1:n-1 delete!(m…

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## [What is the programmatic way to obtain the path to the base directory?](https://discourse.julialang.org/t/what-is-the-programmatic-way-to-obtain-the-path-to-the-base-directory/83687)

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**Author:** [@jishnub](https://discourse.julialang.org/u/jishnub)\
**Replies:** 0\
**Last updated:** [July 3, 2022, 6:01am UTC](https://discourse.julialang.org/t/what-is-the-programmatic-way-to-obtain-the-path-to-the-base-directory/83687 "2022-07-03T06:01:54Z")

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On v1.7, using a downloaded binary, joinpath(Sys.BINDIR, Base.DATAROOTDIR, "julia", "base") returns the path to the base directory. On v1.9, however, this has changed, and now julia\> joinpath(Sys.BINDIR, Base.DATAROOT…

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## [An easy way to access files/folders/directories with Julia in command line based on language: batch-script](https://discourse.julialang.org/t/an-easy-way-to-access-files-folders-directories-with-julia-in-command-line-based-on-language-batch-script/79873)

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**Author:** [@anon29721930](https://discourse.julialang.org/u/anon29721930)\
**Replies:** 14\
**Last updated:** [July 2, 2022, 2:57am UTC](https://discourse.julialang.org/t/an-easy-way-to-access-files-folders-directories-with-julia-in-command-line-based-on-language-batch-script/79873 "2022-07-02T02:57:13Z")

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Hi all! Community Julia! user stories I would like as a user to list files, folders, directories like I would in shell script or bat-script in the Julia programming language, because it would be an easy way I would lik…

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## [Develop julia base/\* vs usr/share/julia/src/base/\*](https://discourse.julialang.org/t/develop-julia-base-vs-usr-share-julia-src-base/82643)

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**Author:** [@albheim](https://discourse.julialang.org/u/albheim)\
**Replies:** 9\
**Last updated:** [July 1, 2022, 11:27am UTC](https://discourse.julialang.org/t/develop-julia-base-vs-usr-share-julia-src-base/82643 "2022-07-01T11:27:21Z")

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I had cloned and built julia, and was playing around with some things in base/\*, using Revise.track(Base), and seeing the changes in the REPL as I made them in the files. I restart julia and try to run things again, thou…

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## [\`fill\` is dangerous :-(](https://discourse.julialang.org/t/fill-is-dangerous/83396)

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**Author:** [@sylvaticus](https://discourse.julialang.org/u/sylvaticus)\
**Replies:** 1\
**Last updated:** [June 27, 2022, 11:52am UTC](https://discourse.julialang.org/t/fill-is-dangerous/83396 "2022-06-27T11:52:20Z")

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I propose to add an extra keyword argument to fill (and fill!) to specify copy instead of reference and switch to copy in Julia 2.0 :slight\_smile: While it makes sense to have call by sharing in functions, there is not …

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## [Why throw on overlong slice?](https://discourse.julialang.org/t/why-throw-on-overlong-slice/83345)

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**Author:** [@jar1](https://discourse.julialang.org/u/jar1)\
**Replies:** 7\
**Last updated:** [June 26, 2022, 11:29pm UTC](https://discourse.julialang.org/t/why-throw-on-overlong-slice/83345 "2022-06-26T23:29:22Z")

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Python: In \[1\]: \[1,2\]\[0:4\] Out\[1\]: \[1, 2\] Julia: julia\> \[1,2\]\[1:5\] ERROR: BoundsError: attempt to access 2-element Vector{Int64} at index \[1:5\] Why does Julia throw on overlong slice? Is this somehow useful for perfo…

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## [FFTW MKL sub dimensional FFT create plan failed](https://discourse.julialang.org/t/fftw-mkl-sub-dimensional-fft-create-plan-failed/81086)

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**Author:** [@Lightup1](https://discourse.julialang.org/u/Lightup1)\
**Replies:** 3\
**Last updated:** [June 25, 2022, 7:23am UTC](https://discourse.julialang.org/t/fftw-mkl-sub-dimensional-fft-create-plan-failed/81086 "2022-06-25T07:23:31Z")

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MKL provider failed for plan sub dimension FFT. test=Array{ComplexF64}(undef, \[\[4,4\];\[4,4\]\]...); p1=plan\_fft(test,\[3,4\]) result1=fft(reshape(\[1:4^4;\],4,4,4,4)) result2=p1\*reshape(\[1:4^4;\],4,4,4,4) result1==result2 #fals…

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## [How are invalidated MethodInstances found, and how well does the process scale?](https://discourse.julialang.org/t/how-are-invalidated-methodinstances-found-and-how-well-does-the-process-scale/83099)

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**Author:** [@Benny](https://discourse.julialang.org/u/Benny)\
**Replies:** 7\
**Last updated:** [June 22, 2022, 7:54am UTC](https://discourse.julialang.org/t/how-are-invalidated-methodinstances-found-and-how-well-does-the-process-scale/83099 "2022-06-22T07:54:52Z")

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From what I understand, compiled methods (for clarity I’ll call them MethodInstances) are invalidated when methods are defined, e.g. f(x) = 1; f(1); f(x::Real) = 2. I imagine the most wasteful algorithm would be to check…

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## [Different Errors on CI and local machine](https://discourse.julialang.org/t/different-errors-on-ci-and-local-machine/83120)

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**Author:** [@fbanning](https://discourse.julialang.org/u/fbanning)\
**Replies:** 3\
**Last updated:** [June 22, 2022, 6:22am UTC](https://discourse.julialang.org/t/different-errors-on-ci-and-local-machine/83120 "2022-06-22T06:22:13Z")

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I’m encountering an issue with CI on github. If I define julia\> foo(x) = nothing foo (generic function with 1 method) and do a @test\_throws with it, I would expect it to throw a MethodError like here julia\> foo(; x =…

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