# Internals & Design

**URL:** https://discourse.julialang.org/c/dev/5.md?page=61

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

**Page:** 62

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## [Recent Metadata.jl PRs](https://discourse.julialang.org/t/recent-metadata-jl-prs/10309)

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**Author:** [@ccoffrin](https://discourse.julialang.org/u/ccoffrin)\
**Replies:** 1\
**Last updated:** [April 12, 2018, 9:43pm UTC](https://discourse.julialang.org/t/recent-metadata-jl-prs/10309 "2018-04-12T21:43:59Z")

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It seems like the Metadata PRs have not been merged in some time (about 5 days?), is there a freeze in progress?

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## [Dot-macro, in-place ops for immutables](https://discourse.julialang.org/t/dot-macro-in-place-ops-for-immutables/10270)

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**Author:** [@foobar\_lv2](https://discourse.julialang.org/u/foobar_lv2)\
**Replies:** 7\
**Last updated:** [April 11, 2018, 10:06pm UTC](https://discourse.julialang.org/t/dot-macro-in-place-ops-for-immutables/10270 "2018-04-11T22:06:30Z")

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I just got a speed-up of factor ~17 on some BigInt code by using inplace operations, see https://discourse.julialang.org/t/a-plea-for-int-overflow-checking-as-the-default/3338/75?u=foobar\_lv2. Consider the line n=3\*n+1,…

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## ["SystemError: edit: No error" when EDITOR unset in Windows](https://discourse.julialang.org/t/systemerror-edit-no-error-when-editor-unset-in-windows/10278)

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**Author:** [@digital\_carver](https://discourse.julialang.org/u/digital_carver)\
**Replies:** 0\
**Last updated:** [April 11, 2018, 12:08pm UTC](https://discourse.julialang.org/t/systemerror-edit-no-error-when-editor-unset-in-windows/10278 "2018-04-11T12:08:20Z")

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A rather minor thing in the overall scheme of things, but @edit on Windows gives this rather strange error message when I try the macro without setting an EDITOR or JULIA\_EDITOR variable. julia\> @edit sin(42) ERROR: Sys…

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## [Guidelines on when to optimize code](https://discourse.julialang.org/t/guidelines-on-when-to-optimize-code/10268)

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**Author:** [@jlapeyre](https://discourse.julialang.org/u/jlapeyre)\
**Replies:** 5\
**Last updated:** [April 11, 2018, 6:11am UTC](https://discourse.julialang.org/t/guidelines-on-when-to-optimize-code/10268 "2018-04-11T06:11:25Z")

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I poked around a bit but did not find guidelines on when a simple opportunity for optimization should be taken. I’m not concerned about end-user code, rather both the core and packages. Perhaps the main issue is code co…

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## [Is seeking a binary sequence on \`IOStream\` built in?](https://discourse.julialang.org/t/is-seeking-a-binary-sequence-on-iostream-built-in/10184)

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**Author:** [@standarddeviant](https://discourse.julialang.org/u/standarddeviant)\
**Replies:** 2\
**Last updated:** [April 10, 2018, 9:49pm UTC](https://discourse.julialang.org/t/is-seeking-a-binary-sequence-on-iostream-built-in/10184 "2018-04-10T21:49:59Z")

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I needed a function that I’m calling “seek\_binary\_sequence”. I’m writing binary data files, and looking for a “magic sequence” of bytes. I think a reasonable implementation is as follows function seek\_binary\_sequence(…

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## [read methods for composite types](https://discourse.julialang.org/t/read-methods-for-composite-types/10262)

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**Author:** [@miromarszal](https://discourse.julialang.org/u/miromarszal)\
**Replies:** 0\
**Last updated:** [April 10, 2018, 12:30pm UTC](https://discourse.julialang.org/t/read-methods-for-composite-types/10262 "2018-04-10T12:30:40Z")

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I wasn’t sure whether it’s a bug or intended behaviour, so I’m posting it here. I run into a possible inconsistency in read methods when applied to a composite type. See the following example. Let’s create a simple com…

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## [Deprecated call to trunc in loading.jl](https://discourse.julialang.org/t/deprecated-call-to-trunc-in-loading-jl/10249)

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**Author:** [@ScottPJones](https://discourse.julialang.org/u/ScottPJones)\
**Replies:** 0\
**Last updated:** [April 9, 2018, 5:30pm UTC](https://discourse.julialang.org/t/deprecated-call-to-trunc-in-loading-jl/10249 "2018-04-09T17:30:11Z")

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The following line needs to be updated for v0.7: https://github.com/JuliaLang/julia/blob/master/base/loading.jl#L1391 trunc(ftime\_req, 6) =\> trunc(ftime\_req; digits=6)

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## [Scope and global in REPL (julia 0.7)](https://discourse.julialang.org/t/scope-and-global-in-repl-julia-0-7/10233)

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**Author:** [@oheil](https://discourse.julialang.org/u/oheil)\
**Replies:** 3\
**Last updated:** [April 9, 2018, 2:53pm UTC](https://discourse.julialang.org/t/scope-and-global-in-repl-julia-0-7/10233 "2018-04-09T14:53:22Z")

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x=1; while x\<10 x+=1 end ┌ Warning: Deprecated syntax \`implicit assignment to global variable \`x\`\`. │ Use \`global x\` instead. └ @ nothing none:0 I think while should not open a new scope of variables. In more comple…

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## [The death of optional arguments?](https://discourse.julialang.org/t/the-death-of-optional-arguments/7388)

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**Author:** [@bramtayl](https://discourse.julialang.org/u/bramtayl)\
**Replies:** 37\
**Last updated:** [April 9, 2018, 2:08pm UTC](https://discourse.julialang.org/t/the-death-of-optional-arguments/7388 "2018-04-09T14:08:49Z")

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With NamedTuple keyword arguments and constant propagation pull requests both open, it sounds like keyword arguments will soon be type stable and fast. Does this spell the end for optional arguments? Keyword arguments ha…

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## [Appveyor tests Julia Version 0.7.0-DEV.4810, but nightlies only has 4690?](https://discourse.julialang.org/t/appveyor-tests-julia-version-0-7-0-dev-4810-but-nightlies-only-has-4690/10226)

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**Author:** [@PetrKryslUCSD](https://discourse.julialang.org/u/PetrKryslUCSD)\
**Replies:** 1\
**Last updated:** [April 8, 2018, 5:51am UTC](https://discourse.julialang.org/t/appveyor-tests-julia-version-0-7-0-dev-4810-but-nightlies-only-has-4690/10226 "2018-04-08T05:51:21Z")

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Is an update needed?

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## [Ridiculous idea: types from the future](https://discourse.julialang.org/t/ridiculous-idea-types-from-the-future/5457)

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**Author:** [@rdeits](https://discourse.julialang.org/u/rdeits)\
**Replies:** 16\
**Last updated:** [April 6, 2018, 10:03pm UTC](https://discourse.julialang.org/t/ridiculous-idea-types-from-the-future/5457 "2018-04-06T22:03:39Z")

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I’ve been thinking about a pattern that often comes up when I write Julia code. I frequently find myself creating a vector and then appending elements to that vector within a loop. But that raises the question of how to …

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## [Time for re-writing?](https://discourse.julialang.org/t/time-for-re-writing/10196)

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**Author:** [@Nosferican](https://discourse.julialang.org/u/Nosferican)\
**Replies:** 8\
**Last updated:** [April 6, 2018, 4:04pm UTC](https://discourse.julialang.org/t/time-for-re-writing/10196 "2018-04-06T16:04:55Z")

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As Julia develops and moves to the 1.0 milestone I wanted to get some opinions about whether it might be worthwhile to re-write various packages. Many widely used packages have been developed since the early days, (e.g.,…

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## [Building julia with Intel MKL: libimf not found](https://discourse.julialang.org/t/building-julia-with-intel-mkl-libimf-not-found/10171)

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**Author:** [@v-i-s-h](https://discourse.julialang.org/u/v-i-s-h)\
**Replies:** 4\
**Last updated:** [April 6, 2018, 12:34am UTC](https://discourse.julialang.org/t/building-julia-with-intel-mkl-libimf-not-found/10171 "2018-04-06T00:34:54Z")

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Hi, I’m trying to build julia (tag v0.6.2) from source. I have already installed intel MKL, IPP, TBB and MPI in my system (elementaryOS 0.4.1, based on Ubuntu 16.04) and setup the compiler variable using the script in /…

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## [Fix1 (analogue of Base.Fix2)](https://discourse.julialang.org/t/fix1-analogue-of-base-fix2/10161)

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**Author:** [@Tamas\_Papp](https://discourse.julialang.org/u/Tamas_Papp)\
**Replies:** 11\
**Last updated:** [April 5, 2018, 8:16pm UTC](https://discourse.julialang.org/t/fix1-analogue-of-base-fix2/10161 "2018-04-05T20:16:32Z")

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I was very happy to see Base.Fix2 since it saves typing for creating closures. Would it make sense to introduce a Fix1 that does the same, except for fixing the first argument?

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## [Changed Expr args for :(:) in 0.7?](https://discourse.julialang.org/t/changed-expr-args-for-in-0-7/10167)

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**Author:** [@chakravala](https://discourse.julialang.org/u/chakravala)\
**Replies:** 2\
**Last updated:** [April 5, 2018, 5:06am UTC](https://discourse.julialang.org/t/changed-expr-args-for-in-0-7/10167 "2018-04-05T05:06:09Z")

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In Julia v0.6: julia\> :(2:34) |\> dump Expr head: Symbol : args: Array{Any}((2,)) 1: Int64 2 2: Int64 34 typ: Any In Julia v0.7 julia\> :(2:34) |\> dump Expr head: Symbol call args: Array{Any}((3,)) …

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## [Should every method in Base be documented?](https://discourse.julialang.org/t/should-every-method-in-base-be-documented/10143)

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**Author:** [@tparker](https://discourse.julialang.org/u/tparker)\
**Replies:** 7\
**Last updated:** [April 3, 2018, 9:52pm UTC](https://discourse.julialang.org/t/should-every-method-in-base-be-documented/10143 "2018-04-03T21:52:02Z")

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Is the Julia developers’ policy that every method in the Base module should be documented, or that in order to avoid clutter, it’s okay to omit documentation for methods that are fairly minor variants on other, documente…

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## [Missing data and NamedTuple compatibility](https://discourse.julialang.org/t/missing-data-and-namedtuple-compatibility/8136)

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**Author:** [@piever](https://discourse.julialang.org/u/piever)\
**Replies:** 91\
**Last updated:** [April 2, 2018, 10:34am UTC](https://discourse.julialang.org/t/missing-data-and-namedtuple-compatibility/8136 "2018-04-02T10:34:30Z")

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By adding support for missing data and NamedTuples Julia is offering very solid foundations to build a data ecosystem upon. While I’m extremely happy that these two features have been added (especially given the extensiv…

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## [Nasty Base.show() recursive stack backtrace error](https://discourse.julialang.org/t/nasty-base-show-recursive-stack-backtrace-error/10088)

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**Author:** [@iwelch](https://discourse.julialang.org/u/iwelch)\
**Replies:** 2\
**Last updated:** [March 31, 2018, 7:42pm UTC](https://discourse.julialang.org/t/nasty-base-show-recursive-stack-backtrace-error/10088 "2018-03-31T19:42:38Z")

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julia\> struct FFF; fv::Float64; end#struct julia\> Base.show(io::IO, f::FFF) = println(io, "Your FFF type is $f.fv") julia\> f= FFF(2.0) I do not yet know why this is not working, but it will probably be obvious to me s…

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## [Propose for a movable SubArray](https://discourse.julialang.org/t/propose-for-a-movable-subarray/10066)

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**Author:** [@cnliao](https://discourse.julialang.org/u/cnliao)\
**Replies:** 6\
**Last updated:** [March 31, 2018, 5:43am UTC](https://discourse.julialang.org/t/propose-for-a-movable-subarray/10066 "2018-03-31T05:43:36Z")

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As is known views themselves need memory to hold some information. The fact that views are often used as temporaries leads to unnecessary (de)allocations when the same view is used multiple times. Moreover, this behavior…

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## [Use of MurmurHash3 for hashing strings](https://discourse.julialang.org/t/use-of-murmurhash3-for-hashing-strings/9818)

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**Author:** [@ScottPJones](https://discourse.julialang.org/u/ScottPJones)\
**Replies:** 29\
**Last updated:** [March 30, 2018, 12:47pm UTC](https://discourse.julialang.org/t/use-of-murmurhash3-for-hashing-strings/9818 "2018-03-30T12:47:55Z")

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Julia uses the 128 bit MurmurHash3 algorithm for the hash function for AbstractString. There are two serious issues with that: It is not possible to build up a hash value for a string in chunks: julia\> hash("bar",has…

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## [Pmap feature for dynamic decisions](https://discourse.julialang.org/t/pmap-feature-for-dynamic-decisions/10050)

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**Author:** [@iwelch](https://discourse.julialang.org/u/iwelch)\
**Replies:** 2\
**Last updated:** [March 30, 2018, 12:34am UTC](https://discourse.julialang.org/t/pmap-feature-for-dynamic-decisions/10050 "2018-03-30T00:34:19Z")

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can I ask for feedback on a feature request? code that is called by pmap should have the ability to signal to the scheduler a (dynamic) determination not to schedule any more tasks. existing tasks should either be fini…

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## [Selectdim fails to recognize IndexLinear](https://discourse.julialang.org/t/selectdim-fails-to-recognize-indexlinear/10053)

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**Author:** [@cnliao](https://discourse.julialang.org/u/cnliao)\
**Replies:** 1\
**Last updated:** [March 29, 2018, 8:01pm UTC](https://discourse.julialang.org/t/selectdim-fails-to-recognize-indexlinear/10053 "2018-03-29T20:01:34Z")

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I am on the latest master and wondering if the following behaviors considered bugs: selectdim and view returns different types of SubArrays, which is surprising. When N\>2 the last type parameter of the returned SubArra…

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## [FunctionWrappers in stdlib?](https://discourse.julialang.org/t/functionwrappers-in-stdlib/10007)

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**Author:** [@ExpandingMan](https://discourse.julialang.org/u/ExpandingMan)\
**Replies:** 5\
**Last updated:** [March 28, 2018, 2:04pm UTC](https://discourse.julialang.org/t/functionwrappers-in-stdlib/10007 "2018-03-28T14:04:53Z")

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I think we should have this, see this issue for a description of what those are and my argument for why it should be in stdlib. These are currently used in ReverseDiff.jl. See my simulator of a MOS 6502 CPU for another…

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## [What we need to do IO in Julia with guaranteed memory safety](https://discourse.julialang.org/t/what-we-need-to-do-io-in-julia-with-guaranteed-memory-safety/9976)

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**Author:** [@ExpandingMan](https://discourse.julialang.org/u/ExpandingMan)\
**Replies:** 11\
**Last updated:** [March 28, 2018, 1:28am UTC](https://discourse.julialang.org/t/what-we-need-to-do-io-in-julia-with-guaranteed-memory-safety/9976 "2018-03-28T01:28:05Z")

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(I was going to post this as an issue on the Julia github, but I still feel I’m a little naive in this topic so I wanted to open it up to discussion here, see what people think, then post a real issue. I know there’s a …

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## [RHS or LHS assignment?](https://discourse.julialang.org/t/rhs-or-lhs-assignment/9940)

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**Author:** [@wood](https://discourse.julialang.org/u/wood)\
**Replies:** 8\
**Last updated:** [March 24, 2018, 4:46pm UTC](https://discourse.julialang.org/t/rhs-or-lhs-assignment/9940 "2018-03-24T16:46:32Z")

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There are extensive discussions about RHS and LHS assignment in Julia github about = (see 13168, 5532, 7341 ) and .= (see 26516, 25954, 26088, 26347). But it seems that these are still controversial. I think it would be…

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## [Distinguishing projects from packages](https://discourse.julialang.org/t/distinguishing-projects-from-packages/153)

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**Author:** [@djsegal](https://discourse.julialang.org/u/djsegal)\
**Replies:** 38\
**Last updated:** [March 23, 2018, 7:31pm UTC](https://discourse.julialang.org/t/distinguishing-projects-from-packages/153 "2018-03-23T19:31:05Z")

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old title: "Extending PkgDev.jl to Project Generation" edit: the title was changed to reflect what gets discussed. however this starting post (below) remains unedited to highlight the question that provoked it From P…

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## [Regression in v0.7 due to weird inference failure for function with Lisp-y recursion](https://discourse.julialang.org/t/regression-in-v0-7-due-to-weird-inference-failure-for-function-with-lisp-y-recursion/9342)

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**Author:** [@pablosanjose](https://discourse.julialang.org/u/pablosanjose)\
**Replies:** 14\
**Last updated:** [March 23, 2018, 6:46pm UTC](https://discourse.julialang.org/t/regression-in-v0-7-due-to-weird-inference-failure-for-function-with-lisp-y-recursion/9342 "2018-03-23T18:46:21Z")

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Consider this example, where foo works out a type given some inputs of other types: mutable struct A{E, L} end mutable struct B{E, L} end mutable struct C{E, L} end foo(::Type{T}, t, ts...) where {T} = foo(foo(T, t),…

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## [Issue with return values of new 3 argument prevind and nextind functions](https://discourse.julialang.org/t/issue-with-return-values-of-new-3-argument-prevind-and-nextind-functions/9910)

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**Author:** [@ScottPJones](https://discourse.julialang.org/u/ScottPJones)\
**Replies:** 2\
**Last updated:** [March 23, 2018, 2:29am UTC](https://discourse.julialang.org/t/issue-with-return-values-of-new-3-argument-prevind-and-nextind-functions/9910 "2018-03-23T02:29:06Z")

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In cases where the number of characters plus the starting position is greater than ncodeunits(str)+1, nextind should really return (as documented) ncodeunits(str)+1. Also, if nchar is 0, nextind and prevind should act t…

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## [How to get 0.7.0-DEV.4652 from commit hash?](https://discourse.julialang.org/t/how-to-get-0-7-0-dev-4652-from-commit-hash/9859)

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**Author:** [@dmbates](https://discourse.julialang.org/u/dmbates)\
**Replies:** 3\
**Last updated:** [March 21, 2018, 8:28pm UTC](https://discourse.julialang.org/t/how-to-get-0-7-0-dev-4652-from-commit-hash/9859 "2018-03-21T20:28:12Z")

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I think I have seen this but I can’t find it now. I want to check for Julia versions where the second form from Warning: \`sum(a::AbstractArray, dims)\` is deprecated, use \`sum(a, dims=dims)\` instead. is valid. The com…

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## [Command pattern](https://discourse.julialang.org/t/command-pattern/9832)

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**Author:** [@yakir12](https://discourse.julialang.org/u/yakir12)\
**Replies:** 2\
**Last updated:** [March 20, 2018, 11:47am UTC](https://discourse.julialang.org/t/command-pattern/9832 "2018-03-20T11:47:37Z")

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Just checking: is anyone working on or has ideas about command pattern in Julia? I’m working on the front-end of a program and it feels like it might get a lot simpler if I could save the data the user is inputing in th…

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