# Svec not documented

**URL:** <https://discourse.julialang.org/t/svec-not-documented/63945>\
**Category:** Internals & Design\
**Tags:** documentation, svec\
**Created:** [July 2, 2021, 3:00pm UTC](https://discourse.julialang.org/t/svec-not-documented/63945 "2021-07-02T15:00:02Z")\
**Posts on this page:** 4\
**Page:** 1

<div class="post-metadata">

**Author:** ![nandoconde](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/nandoconde/32/19497_2.png) [@nandoconde](https://discourse.julialang.org/u/nandoconde)\
**Post date:** [July 2, 2021, 3:00pm UTC](https://discourse.julialang.org/t/svec-not-documented/63945/1 "2021-07-02T15:00:02Z")

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Hello!

I know that it is a very “internals” thing, but `svec` is not documented anywhere in the docs. Also, this is rather unhelpful:

```julia
help?> Core.svec
  No documentation found.

  Core.svec is a Function.

  # built-in function; no methods

julia>

```

Is there any reason for this?

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<div class="post-metadata">

**Author:** ![Gnimuc](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/gnimuc/32/2194_2.png) [@Gnimuc](https://discourse.julialang.org/u/Gnimuc)\
**Post date:** [July 2, 2021, 4:16pm UTC](https://discourse.julialang.org/t/svec-not-documented/63945/2 "2021-07-02T16:16:42Z")

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It’s used as a vector at certain stage when other container types in `Base` are not defined yet. You can find the definition here: [julia/simplevector.c at b46df09eb651eba97776fe73e8044e0456e81320 · JuliaLang/julia · GitHub](https://github.com/JuliaLang/julia/blob/b46df09eb651eba97776fe73e8044e0456e81320/src/simplevector.c#L10-L20) and the definition of `Core.SimpleVector`: [julia/julia.h at b46df09eb651eba97776fe73e8044e0456e81320 · JuliaLang/julia · GitHub](https://github.com/JuliaLang/julia/blob/b46df09eb651eba97776fe73e8044e0456e81320/src/julia.h#L163-L170)

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<div class="post-metadata">

**Author:** ![nandoconde](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/nandoconde/32/19497_2.png) [@nandoconde](https://discourse.julialang.org/u/nandoconde)\
**Post date:** [July 2, 2021, 5:01pm UTC](https://discourse.julialang.org/t/svec-not-documented/63945/3 "2021-07-02T17:01:42Z")

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Yep, I could more or less know what it is.

I meant that it is not documented anywhere in the docs, and it does show up commonly when working with types and inference. For example:

```julia
julia> struct multi_param{T, U}
       q::Float64
       r::T
       s::U
       end

julia> obj2 = multi_param(8.0,9,10)
multi_param{Int64, Int64}(8.0, 9, 10)

julia> typeof(obj2).parameters
svec(Int64, Int64)

```

I think this should be documented, don’t you think?

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<div class="post-metadata">

**Author:** ![Skoffer](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/skoffer/32/378_2.png) [@Skoffer](https://discourse.julialang.org/u/Skoffer)\
**Post date:** [July 2, 2021, 5:11pm UTC](https://discourse.julialang.org/t/svec-not-documented/63945/4 "2021-07-02T17:11:31Z")

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`.parameters` is considered as a part of internal implementation, so it is potentially subject to change. Probably this is why it is not documented (too much trouble to keep it up to date and those who use it, know it’s behaviour anyway).