Implicit conversion of function arguments only makes sense if there's a well-defined notion of a particular type that is expected when calling a function – that makes sense in languages where functions are monomorphic. In Julia, that's very far from the case – and the combination of inheritance, multiple dispatch and implicit conversion would be total chaos. For typed locations like object fields and array slots (or typed local variables), we do implicit conversion since there is a well-defined type to convert to.
On Tue, Mar 15, 2016 at 11:36 AM, Carlo Lucibello <[email protected] > wrote: > Unfortunately In my use case I would have to add a method for almost > every method exported by another module: > > see https://github.com/JuliaGraphs/Networks.jl/issues/4 > > The easiest way to do would be to use abstraction and inheritance, but in > the other module (LightGraphs) I don't have an abstract type to inherit from > > There is some deeply rooted reason for not having implicit (but explicitly > declared) conversion? > > > Il giorno martedì 15 marzo 2016 15:37:33 UTC+1, Matt Bauman ha scritto: >> >> To generalize this idiom a bit, I think I'd write it as: >> >> Base.convert(::Type{Float64}, a::MyNum) = convert(Float64, a.x) >> f(a) = f(convert(Float64, a)) >> f(a::Float64) = 2. # real algorithm >> >> Of course, this will also allow things like `f(1)`. >> >> >> On Tuesday, March 15, 2016 at 10:18:30 AM UTC-4, Stefan Karpinski wrote: >>> >>> No, there is never any implicit conversion of arguments in Julia. >>> However, all you need to do is add a method to f to get it to do what you >>> want: >>> >>> f(a::MyNum) = convert(Float64, a.x) >>> >>> On Tue, Mar 15, 2016 at 6:54 AM, Carlo Lucibello <[email protected]> >>> wrote: >>> >>>> >>>> >>>> Il giorno martedì 15 marzo 2016 11:51:31 UTC+1, Carlo Lucibello ha >>>> scritto: >>>>> >>>>> Is it possible to have user defined implicit conversion in Julia? >>>>> >>>>> This is an example of how I imagine it should work: >>>>> >>>>> type MyNum >>>>> x >>>>> end >>>>> >>>>> implicit_convert(::Type(Float64), a::MyNum) = convert(Float64, a.x) >>>>> >>>>> f(x::Float64) = 2. >>>>> f(MyNum(1.)) # error, sadly >>>>> >>>>> In C++ this behaviour can be obtained overloading >>>>> >>>> * overloading operator double() >>>> >>>>> PS I don’t want to use inheritance >>>>> >>>>> >>>> >>>
