Multiple dispach method overwritten

Hi, I don’t understand why I’m getting this warning.

WARNING: Method definition grdtrack() in module GMT at c:\j\.julia\v0.6\GMT\src\grdtrack.jl:51 overwritten at c:\j\.julia\v0.6\GMT\src\grdtrack.jl:150.
WARNING: Method definition #grdtrack(Array{Any, 1}, typeof(GMT.grdtrack)) in module GMT overwritten.

The lines in question from this file, read

# ---------------------------------------------------------------------------------------------------
function grdtrack(cmd0::String="", arg1=[], arg2=[]; data=[], kwargs...)
grdtrack(arg1=[], arg2=[], cmd0::String=""; data=[], kw...) = grdtrack(cmd0, arg1, arg2; data=data, kw...)

The type of the positional arguments is not the same, so why does it say it’s the same method?

1 Like

Both methods have defaults for all positional arguments, so if you call grdtrack(), which method should be invoked?

You mean without any argument as in?


Well, for my case it doesn’t matter because without arguments the call is interpreted as a request to print a on line help and quit (which it does correctly)

What I mean is that the ambiguity is for the method with no arguments, grdtrack().
It could match the definition at line 51 or the definition at line 150.


“Optional arguments are actually just a convenient syntax for writing multiple method definitions with different numbers of arguments (see Note on Optional and keyword Arguments).”

Thanks, I understand now what you mean. But what is the difference to this case? Here I also can call foo() and no ambiguity is reported.

julia> foo(a::String="", b=[]; v=false, c=[], kw...) = 1
foo (generic function with 3 methods)

julia> foo(a=[], b::String=""; v=false, c=[], kw...) = foo(b, a; v=false, c=[], kw...)
foo (generic function with 5 methods)

How is the language supposed to know that it doesn’t matter to you?

I think at the REPL for Main module only, the first no-argument foo method is overwritten silently.
But if you wrap into a module, then you’ll get the method overwritten warning:

module Test
    foo(a::String="", b=[]; v=false, c=[], kw...) = 1
    foo(a=[], b::String=""; v=false, c=[], kw...) = foo(b, a; v=false, c=[], kw...)

Also I think method redefinition warnings might change in v0.7:

RFC: only warn for method overwrites if the two modules are different and in interactive mode by KristofferC · Pull Request #23030 · JuliaLang/julia · GitHub

RFC: add command option to remove method redefinition warnings by KristofferC · Pull Request #23002 · JuliaLang/julia · GitHub

Also note that you’ll still have the conflict and overwritten method, just no warning.

Ok, thanks, that explains completely what is going on. But I’m confused with the issues. #23030 is closed and #23002 was merged but I still get the same warnings with v0.7

Only when precompiling?

Only when precompiling?

Is it the expected behavior?


OK, and thanks for pushing this.