# \#stack

**URL:** https://discourse.julialang.org/tag/stack/975.md

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## [Understanding map/mapslices/eachslice/stack](https://discourse.julialang.org/t/understanding-map-mapslices-eachslice-stack/132744)

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**Author:** [@Boris](https://discourse.julialang.org/u/Boris)\
**Replies:** 2\
**Last updated:** [September 29, 2025, 2:22pm UTC](https://discourse.julialang.org/t/understanding-map-mapslices-eachslice-stack/132744 "2025-09-29T14:22:49Z")

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Hi, I’ve been trying to learn to use mapslices and don’t understand the synthax/errors for my use case. Suppose I have # MWE sb = \[true false false; false false false; true true true\] # dimensions (k \\times j) yh = ran…

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## [How to know when objects are stack or heap allocated](https://discourse.julialang.org/t/how-to-know-when-objects-are-stack-or-heap-allocated/103056)

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**Author:** [@opiateblush](https://discourse.julialang.org/u/opiateblush)\
**Replies:** 7\
**Last updated:** [November 8, 2024, 1:12am UTC](https://discourse.julialang.org/t/how-to-know-when-objects-are-stack-or-heap-allocated/103056 "2024-11-08T01:12:20Z")

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I’m currently writing some performance critical code and got a bit confused about stack and heap allocation in Julia. I thought that immutables are usually stack allocated but apparently that is not the case. I’ve made a…

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## [Type-instability of mapreduce vs. map + reduce](https://discourse.julialang.org/t/type-instability-of-mapreduce-vs-map-reduce/121136)

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**Author:** [@gdalle](https://discourse.julialang.org/u/gdalle)\
**Replies:** 18\
**Last updated:** [October 10, 2024, 4:43pm UTC](https://discourse.julialang.org/t/type-instability-of-mapreduce-vs-map-reduce/121136 "2024-10-10T16:43:03Z")

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I’m a bit surprised that in this simple example, f is type-stable but g is not. Is this a JET.jl issue (@aviatesk) or a Julia issue? using JET function f(m, n) blocks = map(1:n) do i ones(m) end ret…

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## [Easy way to plot a circle given as a vector of vectors (pointwise) as line plot?](https://discourse.julialang.org/t/easy-way-to-plot-a-circle-given-as-a-vector-of-vectors-pointwise-as-line-plot/104574)

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**Author:** [@homocomputeris](https://discourse.julialang.org/u/homocomputeris)\
**Replies:** 15\
**Last updated:** [October 5, 2023, 9:30am UTC](https://discourse.julialang.org/t/easy-way-to-plot-a-circle-given-as-a-vector-of-vectors-pointwise-as-line-plot/104574 "2023-10-05T09:30:15Z")

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Is there an easier way to plot a shape (in geometric sense, not Plots.jl’s) given as a vector of points (i.e. 2D-vectors)? using Plots # approximately a circle vector\_of\_points = \[\[0.708441362115303, 1.413585198669223\]…

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## [Reshaping dataframe](https://discourse.julialang.org/t/reshaping-dataframe/78020)

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**Author:** [@rocco\_sprmnt21](https://discourse.julialang.org/u/rocco_sprmnt21)\
**Replies:** 13\
**Last updated:** [March 17, 2022, 2:52pm UTC](https://discourse.julialang.org/t/reshaping-dataframe/78020 "2022-03-17T14:52:34Z")

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I show a way to transform the starting table to have only one “X” per row. I ask for comments on how to do the various steps differently and / or better. For example how to insert an “index” column or how to filter the…