Update on Base.@kwdef versus Parameters.jl

mocalvao · February 22, 2023, 7:57pm

Hi,

I have checked the Stackoverflow topic Difference between @with_kw and Base.@kwdef in Julia?, whose last update is from Oct, 18, 2021, and would like to know whether there should be any drawbacks due to my current preferred use of the package Parameters.jl (with the corresponding macro @with_kw) instead of the default Julia’s Base.@kw_def; in fact, it seems to me the package still has (some/many?) more resources than the default base macro. Is this correct?

Raf · February 22, 2023, 9:26pm

We have property destructuring in Base now, so @unpack isn’t needed:

(; x, y) = someobj

This combined with @kwdef and I’m not sure how much you get from Parameters.jl anymore.

@kwdef is exported now too:

github.com

JuliaLang/julia/blob/e3d366f1966595ba737220df49e220610823b331/base/exports.jl#L776


      
              promote_type,
              instances,
              supertype,
              typeintersect,
              typejoin,
              widen,
          
          
# syntax
              esc,
              gensym,
              @kwdef,
              macroexpand,
              @macroexpand1,
              @macroexpand,
              parse,
          
          
# help and reflection
              code_typed,
              code_lowered,
              fullname,
              functionloc,

ufechner7 · February 22, 2023, 9:49pm

I think that this syntax:

@with_kw mutable struct Settings @deftype Float64
    my_float = 2.0
end

still needs Parameters.jl

As far as I know Base.@kwdef does not support default types for the fields of a struct.

lmiq · February 22, 2023, 10:30pm

Compatibility with Julia 1.6? (for @unpack)

Raf · February 22, 2023, 10:59pm

Sure, but this is a since 2021 update

lmiq · February 22, 2023, 11:23pm

Yeah, but I keep using it because 1.6 is still the LTS.

mocalvao · February 24, 2023, 2:03pm

Have the features mentioned by @mauro3 at the thread at-kwdef support for parametric types and subtypes by simonbyrne · Pull Request #29316 · JuliaLang/julia · GitHub been merged to Base.@kwdef? I list them here for convenience as well:

Four bits which are “missing” are:

allow @asserts in the type body which then get included in the positional inner constructor.

different show method.

type-specific unpack macros

automatic documentation of the type-fields with their defaults

I don’t think the first three are suitable for Base. The last would be nice though, but maybe for another PR.

Raf · February 24, 2023, 5:54pm

type-specific unpack macros

This is what I meant by property destructuring. Do you use the other things?