Freddy,
This is definitely one of the more confusing things about Julia, but it’s the
best current solution anyone has proposed.
The problem with your example is that methods can only be extended to work on
new types if you make their provenance clear. In your example, you would do
something like the following:
module A
export f
f(s::String) = "Some operation with a String";
end
module B
A.f(b::Bool) = "Some operation with a boolean";
end
Absent an explicit qualification of the origin of the “f” name in module B,
Julia assumes that the f method in B is totally unrelated, which effectively
overwrites the f method in A.
— John
On Jan 12, 2014, at 9:48 AM, Freddy Snijder <[email protected]> wrote:
> Hello Julia Users,
>
> I'm new to Julia and came across some behaviour of Julia, related to methods,
> I didn't expect.
>
> Case A) In the REPL, when I define two methods, I get the behaviour I expect:
>
> julia> f(s::String) = "Some operation with a String";
> julia> f(b::Bool) = "Some operation with a boolean";
> julia> f
> f (generic function with 2 methods)
> So far, so good.
>
> Case B) Now if I have a file with this code and load it in to a fresh REPL
> session (using 'include'):
>
> module A
> export f
> f(s::String) = "Some operation with a String";
> end
> module B
> export f
> f(b::Bool) = "Some operation with a boolean";
> end
> then, when stating 'using A' and 'using B', I get a warning that there is a
> conflict with an existing f:
>
> julia> using A
> julia> f
> f (generic function with 1 method)
> julia> using B
> Warning: using B.f in module Main conflicts with an existing identifier.
> julia> f
> f (generic function with 1 method)
> I would have expected that Julia would see this as the same method with two
> different argument definitions, just like in Case A).
> I have multiple modules that define the same methods for different composite
> types, which seems a normal way of working to me.
>
> What am I doing wrong? The way Julia currently handles this seems incorrect
> to me ...
>
> I'm interested to hear your input!
>
> Kind regards,
>
> Freddy
>
> PS : I'm on Julia Version 0.3.0-prerelease+584 (2013-12-19 22:26 UTC), Commit
> 06458fa* (2 days old master), x86_64-apple-darwin13.0.0
>
>
