Julia: Arguments, unexpected behavior

[henrykironde]

https://docs.julialang.org/en/v1/manual/functions/#Optional-Arguments-1

Julia
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  (_)     | (_) (_)    |  Documentation: https://docs.julialang.org
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  | | | | | | |/ _` |  |
  | | |_| | | | (_| |  |  Version 0.7.0 (2018-08-08 06:46 UTC)
 _/ |\__'_|_|_|\__'_|  |  Official http://julialang.org/ release
|__/                   |  x86_64-w64-mingw32

julia> function Date(y::Int64, m::Int64=1, d::Int64=1)
           err = validargs(Date, y, m, d)
               err === nothing || throw(err)
                   return Date(UTD(totaldays(y, m, d)))
                   end
Date (generic function with 3 methods)

julia> Date(2000, 12, 12)
ERROR: UndefVarError: validargs not defined
Stacktrace:
 [1] Date(::Int64, ::Int64, ::Int64) at .\REPL[1]:2
 [2] top-level scope at none:0

julia> function Re_Date(y::Int64, m::Int64=1, d::Int64=1)
           err = validargs(Re_Date, y, m, d)
               err === nothing || throw(err)
                   return Re_Date(UTD(totaldays(y, m, d)))
                   end
Re_Date (generic function with 3 methods)

julia> Re_Date(2000, 12, 12)
ERROR: UndefVarError: validargs not defined
Stacktrace:
 [1] Re_Date(::Int64, ::Int64, ::Int64) at .\REPL[3]:2
 [2] top-level scope at none:0

julia> Re_Date(2000, 12)
ERROR: UndefVarError: validargs not defined
Stacktrace:
 [1] Re_Date(::Int64, ::Int64, ::Int64) at .\REPL[3]:2 (repeats 2 times)
 [2] top-level scope at none:0

julia>

julia> versioninfo()
Julia Version 0.7.0
Commit a4cb80f3ed (2018-08-08 06:46 UTC)
Platform Info:
  OS: Windows (x86_64-w64-mingw32)
  CPU: Intel(R) Core(TM) i7-4790 CPU @ 3.60GHz
  WORD_SIZE: 64
  LIBM: libopenlibm
  LLVM: libLLVM-6.0.0 (ORCJIT, haswell)

[StefanKarpinski]

Please post questions to the Julia discourse discussion forum.

[rdeits]

I think the manual is actually out of date in this case. Dates doesn't export validargs, so it should be Dates.validargs instead of just validargs.

[KristofferC]

This just shows the implementation of a function in the Dates module, it is not something you should define yourself. But if it is confusing, perhaps a toy example would be better.

[henrykironde]

This is not about the Dates module, it is about the default parameters and how they fail when we pass optional arguments

julia> function Re_Date(y::Int64, m::Int64=1, d::Int64=1)
           err = validargs(Re_Date, y, m, d)
               err === nothing || throw(err)
                   return Re_Date(UTD(totaldays(y, m, d)))
                   end
Re_Date (generic function with 3 methods)

julia> Re_Date(2000, 12, 12)
ERROR: UndefVarError: validargs not defined
Stacktrace:
 [1] Re_Date(::Int64, ::Int64, ::Int64) at .\REPL[3]:2
 [2] top-level scope at none:0

[KristofferC]

The problem is that validargs is not defined in Main (where you run the code). It is defined in Dates. It has nothing to do with optional arguments.

[henrykironde]

Thanks so much @KristofferC.
So would this function be a clean function to test with

function foo(y::Int64, m::Int64=1, d::Int64=5)
    a = y+m+d
    printf(a)
    return a
end

[KristofferC]

Yeah, except that we don't have printf :)

[henrykironde]

I have tried to run it but it fails.

[KristofferC]

we don't have printf :)

[henrykironde]

Sorry about that. Revised

function foo(y::Int64, m::Int64=1, d::Int64=5)
    a = y+m+d
    return a
end

[henrykironde]

I have tried this on mac and it pass but still fails on windows

versioninfo()
Julia Version 0.7.0
Commit a4cb80f3ed (2018-08-08 06:46 UTC)
Platform Info:
  OS: Linux (x86_64-pc-linux-gnu)
  CPU: Intel(R) Core(TM) i5-5287U CPU @ 2.90GHz
  WORD_SIZE: 64
  LIBM: libopenlibm
  LLVM: libLLVM-6.0.0 (ORCJIT, broadwell)
Environment:
  JULIA_PATH = /usr/local/julia
  JULIA_GPG = 3673DF529D9049477F76B37566E3C7DC03D6E495
  JULIA_VERSION = 0.7.0

But fails on windows

Julia Version 0.7.0
Commit a4cb80f3ed (2018-08-08 06:46 UTC)
Platform Info:
  OS: Windows (x86_64-w64-mingw32)
  CPU: Intel(R) Core(TM) i7-4790 CPU @ 3.60GHz
  WORD_SIZE: 64
  LIBM: libopenlibm
  LLVM: libLLVM-6.0.0 (ORCJIT, haswell)

[fredrikekre]

Please post questions to the Julia discourse discussion forum.

[StefanKarpinski]

Indeed, please, continue the conversation on discourse.