Standard Module Main, Core, Base definition

Hawk · May 8, 2022, 2:07pm

In Julia Manual, it says that “There are three important standard modules: Main, Core, and Base.”, But I just wonder where are these modules defined, can we find their file path? By the way, are there smart methods to find file path where certain function is defined within Julia?

jling · May 8, 2022, 2:09pm

try running this in REPL

@which sin(3.0)
# or
@edit sin(3.0)

Hawk · May 8, 2022, 2:14pm

Thanks, macro @which and @edit are clever ideas to find file path where their definitions locate. So is there the similar method to find definition for Module like Main and Core, because when I type @which for Core and Main, it shows:

@which Core
Main
@which Main
Main

But I still do not know where they locate

jling · May 8, 2022, 2:15pm

their definition is not useful, because they essentially made up the Julia as you know:

github.com

JuliaLang/julia/blob/d4acead9130f97f0135bee604d94e1f67dabc70f/base/Base.jl#L3


      
          # This file is a part of Julia. License is MIT: https://julialang.org/license
          
          
baremodule Base
          
          
using Core.Intrinsics, Core.IR
          
          
# to start, we're going to use a very simple definition of `include`
          # that doesn't require any function (except what we can get from the `Core` top-module)
          const _included_files = Array{Tuple{Module,String},1}()
          function include(mod::Module, path::String)
              ccall(:jl_array_grow_end, Cvoid, (Any, UInt), _included_files, UInt(1))
              Core.arrayset(true, _included_files, (mod, ccall(:jl_prepend_cwd, Any, (Any,), path)), arraylen(_included_files))
              Core.println(path)

they are important in the sense that they exist (almost) universally whenever you use Julia.

Besides Base, Main is your top level in REPL, and Core is not defined from Julia (think of it has bootstrap).

Again, their exact definition is not important, because it’s basically what makes Julia usable for you

Hawk · May 8, 2022, 2:17pm

So how are you find their locations so quickly, any good ideas?

jling · May 8, 2022, 2:18pm

it’s in base/Base.jl, the convention is module X top level locates in a file named X.jl… that’s all…

github.com

JuliaLang/Example.jl/blob/9f288cc4864dbfc2c82338caac0b1eb1fc7ff87f/src/Example.jl#L1


      
          module Example
          export hello, domath
          
          
"""
              hello(who::String)
          
          
Return "Hello, `who`".
          """
          hello(who::String) = "Hello, $who"
          
          
"""

Hawk · May 8, 2022, 2:27pm

Thanks. I see, at present, digging into julia too much about all stuffs seems not a good idea for me…

yashi · May 9, 2022, 11:58am

Yeah, I can feel that.

For a noob like me, a macro or a function to print where the given functions, variables, modules, or any objects would be a great help. I don’t care I actually understand it. I just want to read them for learning.

At first, I didn’t understand why edit() doesn’t work for Core, Main, or Base. But it works for InteractiveUtils.

Also, edit() can handle modules but less() doesn’t seems so.

julia> names(Main)
4-element Vector{Symbol}:
 :Base
 :Core
 :InteractiveUtils
 :Main

julia> edit(Base)
ERROR: object is not callable
Stacktrace:
 [1] error(s::String)
   @ Base ./error.jl:33
 [2] functionloc(f::Any)
   @ Base ./methodshow.jl:182
 [3] edit(f::Any)
   @ InteractiveUtils ~/julia-1.7.2/share/julia/stdlib/v1.7/InteractiveUtils/src/editless.jl:229
 [4] edit(m::Module)
   @ InteractiveUtils ~/julia-1.7.2/share/julia/stdlib/v1.7/InteractiveUtils/src/editless.jl:236
 [5] top-level scope
   @ REPL[2]:1

julia> edit(Core)
ERROR: object is not callable
Stacktrace:
 [1] error(s::String)
   @ Base ./error.jl:33
 [2] functionloc(f::Any)
   @ Base ./methodshow.jl:182
 [3] edit(f::Any)
   @ InteractiveUtils ~/julia-1.7.2/share/julia/stdlib/v1.7/InteractiveUtils/src/editless.jl:229
 [4] edit(m::Module)
   @ InteractiveUtils ~/julia-1.7.2/share/julia/stdlib/v1.7/InteractiveUtils/src/editless.jl:236
 [5] top-level scope
   @ REPL[3]:1

julia> edit(Main)
ERROR: object is not callable
Stacktrace:
 [1] error(s::String)
   @ Base ./error.jl:33
 [2] functionloc(f::Any)
   @ Base ./methodshow.jl:182
 [3] edit(f::Any)
   @ InteractiveUtils ~/julia-1.7.2/share/julia/stdlib/v1.7/InteractiveUtils/src/editless.jl:229
 [4] edit(m::Module)
   @ InteractiveUtils ~/julia-1.7.2/share/julia/stdlib/v1.7/InteractiveUtils/src/editless.jl:236
 [5] top-level scope
   @ REPL[4]:1

julia> edit(InteractiveUtils)

julia>

yashi · May 9, 2022, 12:07pm

You can actually read edit() to see how it finds various objects:

function edit(@nospecialize f)
    ms = methods(f).ms
    length(ms) == 1 && edit(functionloc(ms[1])...)
    length(ms) > 1 && return ms
    length(ms) == 0 && functionloc(f) # throws
    nothing
end
edit(m::Method) = edit(functionloc(m)...)
edit(@nospecialize(f), idx::Integer) = edit(methods(f).ms[idx])
edit(f, t)  = (@nospecialize; edit(functionloc(f, t)...))
edit(file::Nothing, line::Integer) = error("could not find source file for function")
edit(m::Module) = edit(pathof(m))

And Base.module_keys to see how the Module are managed internally. Note that Core, Main, and Base are [top-level].

julia> Base.module_keys
IdDict{Module, Base.PkgId} with 44 entries:
  DelimitedFiles     => DelimitedFiles [8bb1440f-4735-579b-a4ab-409b98df4dab]
  SuiteSparse        => SuiteSparse [4607b0f0-06f3-5cda-b6b1-a6196a1729e9]
  Downloads          => Downloads [f43a241f-c20a-4ad4-852c-f6b1247861c6]
  LibCURL_jll        => LibCURL_jll [deac9b47-8bc7-5906-a0fe-35ac56dc84c0]
  Base64             => Base64 [2a0f44e3-6c83-55bd-87e4-b1978d98bd5f]
  SHA                => SHA [ea8e919c-243c-51af-8825-aaa63cd721ce]
  Artifacts          => Artifacts [56f22d72-fd6d-98f1-02f0-08ddc0907c33]
  LazyArtifacts      => LazyArtifacts [4af54fe1-eca0-43a8-85a7-787d91b784e3]
  CRC32c             => CRC32c [8bf52ea8-c179-5cab-976a-9e18b702a9bc]
  Core               => Core [top-level]
  Main               => Main [top-level]
  SparseArrays       => SparseArrays [2f01184e-e22b-5df5-ae63-d93ebab69eaf]
  Distributed        => Distributed [8ba89e20-285c-5b6f-9357-94700520ee1b]
  Serialization      => Serialization [9e88b42a-f829-5b0c-bbe9-9e923198166b]
  TOML               => TOML [fa267f1f-6049-4f14-aa54-33bafae1ed76]
  Base               => Base [top-level]
  Markdown           => Markdown [d6f4376e-aef5-505a-96c1-9c027394607a]
  ArgTools           => ArgTools [0dad84c5-d112-42e6-8d28-ef12dabb789f]
  nghttp2_jll        => nghttp2_jll [8e850ede-7688-5339-a07c-302acd2aaf8d]
  InteractiveUtils   => InteractiveUtils [b77e0a4c-d291-57a0-90e8-8db25a27a240]
  Sockets            => Sockets [6462fe0b-24de-5631-8697-dd941f90decc]
  Profile            => Profile [9abbd945-dff8-562f-b5e8-e1ebf5ef1b79]
  LibCURL            => LibCURL [b27032c2-a3e7-50c8-80cd-2d36dbcbfd21]
  Libdl              => Libdl [8f399da3-3557-5675-b5ff-fb832c97cbdb]
  Printf             => Printf [de0858da-6303-5e67-8744-51eddeeeb8d7]
  Statistics         => Statistics [10745b16-79ce-11e8-11f9-7d13ad32a3b2]
  SharedArrays       => SharedArrays [1a1011a3-84de-559e-8e89-a11a2f7dc383]
  Random             => Random [9a3f8284-a2c9-5f02-9a11-845980a1fd5c]
  MozillaCACerts_jll => MozillaCACerts_jll [14a3606d-f60d-562e-9121-12d972cd8159]
  p7zip_jll          => p7zip_jll [3f19e933-33d8-53b3-aaab-bd5110c3b7a0]
  Tar                => Tar [a4e569a6-e804-4fa4-b0f3-eef7a1d5b13e]
  LinearAlgebra      => LinearAlgebra [37e2e46d-f89d-539d-b4ee-838fcccc9c8e]
  FileWatching       => FileWatching [7b1f6079-737a-58dc-b8bc-7a2ca5c1b5ee]
  Logging            => Logging [56ddb016-857b-54e1-b83d-db4d58db5568]
  Pkg                => Pkg [44cfe95a-1eb2-52ea-b672-e2afdf69b78f]
  Mmap               => Mmap [a63ad114-7e13-5084-954f-fe012c677804]
  Unicode            => Unicode [4ec0a83e-493e-50e2-b9ac-8f72acf5a8f5]
  LibGit2            => LibGit2 [76f85450-5226-5b5a-8eaa-529ad045b433]
  Dates              => Dates [ade2ca70-3891-5945-98fb-dc099432e06a]
  UUIDs              => UUIDs [cf7118a7-6976-5b1a-9a39-7adc72f591a4]
  REPL               => REPL [3fa0cd96-eef1-5676-8a61-b3b8758bbffb]
  NetworkOptions     => NetworkOptions [ca575930-c2e3-43a9-ace4-1e988b2c1908]
  Test               => Test [8dfed614-e22c-5e08-85e1-65c5234f0b40]
  Future             => Future [9fa8497b-333b-5362-9e8d-4d0656e87820]