Got it, thanks. S.
On Saturday, 20 February 2016 18:44:35 UTC, Yichao Yu wrote: > > On Sat, Feb 20, 2016 at 12:58 PM, Samuel Powell <[email protected] > <javascript:>> wrote: > > In 0.4.3, I have defined the following immutable, with a conversion rule > to > > permit change the type of the wrapped tuple: > > > > immutable Foo{N,T} > > co::NTuple{N,T} > > end > > > > convert{N,T}(::Type{Foo{N,T}}, input::Foo{N}) = Foo( ([T(input.co[i]) > for i > > in input.co]...) ) > > > > Bar = Foo((1.,2.)) # Returns Foo{2, Float64}((1.0,2.0)) > > > > I can explicitly call the convert function: > > > > convert(Foo{2,Float32}, Bar) Returns Foo{2,Float32}((1.0f0, 2.0f0)) > > > > I expected that calling the constructor with the desired parameters > would > > achieve the same, but in fact I receive an error: > > > > Foo{2,Float32}(Bar) # ERROR: MethodError: `convert` has no method > matching > > convert(::Type{Tuple{Float32,Float32}}, ::Foo{2,Float64}) > > > > I do not understand why Julia is dispatching to convert with an argument > of > > ::Type{Tuple{Float32,Float32}}, instead of ::Type{Foo{2,Float32}}, can > > someone shed some light on what's going on? > > See https://github.com/JuliaLang/julia/issues/15120 > > Defining convert does NOT define a constructor for you. In this case, > it perferred the default constructor of the `Foo` type. (See > `methods(Foo)`) > > > > > Regards, > > > > Sam. > > >
