Oh I see! thanks guys. Now I understand what that last line in the point
example in the manual
http://julia.readthedocs.org/en/latest/manual/constructors/#parametric-constructors
was supposed to do. I thought that was an alternative way of ... defining
the type? not really - and that's where I stopped. my bad! :-)
cheers
florian
On Wednesday, 11 June 2014 17:00:13 UTC+1, Tim Holy wrote:
>
> Normally Julia creates the inner and outer constructors for you, but if
> you
> supply your own inner constructor you need to explicitly supply the outer
> one
> too:
>
> julia> type Myt{ T<:Real}
> n :: Int64
> chain :: Array{T,1}
> function Myt(n,z::T)
> x = [z for i=1:n]
> new(n,x)
> end
> end
>
> julia> Myt(5, 3.2f0)
> ERROR: no method Myt{T<:Real}(Int64, Float32)
>
> julia> Myt{T}(n::Integer, z::T) = Myt{T}(n,z)
> Myt{T<:Real} (constructor with 1 method)
>
> julia> Myt(5, 3.2f0)
> Myt{Float32}(5,Float32[3.2,3.2,3.2,3.2,3.2])
>
>
> The declaration of the outer constructor can be a bit confusing: you might
> say, the LHS and RHS look almost identical, so why do you need it? Here's
> the
> translation: "given an integer and a value of type T<:Real, construct a
> Myt{T}
> with those values." You could instead have declared something like
>
> Myt(n::Integer, z::FloatingPoint) = Myt{Float64}(n,float64(z)),
>
> which you'll see gives you considerable flexibility.
>
> --Tim
>
> On Wednesday, June 11, 2014 08:36:51 AM Florian Oswald wrote:
> > hum, good point.
> > however, the same applies if I change this:
> >
> > type Myt{ T<:Real}
> > n :: Int64
> > chain :: Array{T,1}
> > function Myt(n,z::T)
> > x = [z for i=1:n]
> > new(n,x)
> > end
> > end
> >
> > or is that not what you meant? I basically want to fill array "chain"
> with
> > several copies of type T.
> >
> > On Wednesday, 11 June 2014 16:13:47 UTC+1, John Myles White wrote:
> > > Your type’s definition doesn’t seem to depend upon T in any way. Keep
> in
> > > mind that the type is really just the first two lines of your code:
> > >
> > > type Myt{T <: Real}
> > >
> > > n::Int64
> > > chain::Array
> > >
> > > end
> > >
> > > The constructor isn’t part of the type itself, so the dependency on T
> > > needs to occur in the type.
> > >
> > > — John
> > >
> > > On Jun 11, 2014, at 8:04 AM, Florian Oswald <[email protected]
> > > <javascript:>> wrote:
> > >
> > > Hi,
> > >
> > > I'm trying to understand why this is not working:
> > >
> > > type Myt{ T<:Real}
> > >
> > > n :: Int64
> > > chain :: Array
> > > function Myt(n,z::T)
> > >
> > > x = [z for i=1:n]
> > > new(n,x)
> > >
> > > end
> > >
> > > end
> > >
> > > i get the error
> > > julia> Myt(10,18.0)
> > > ERROR: no method Myt{T<:Real}(Int64, Float64)
> > >
> > > I thought that was very similar to the point example on the manual?
> > >
> > > type Point{T<:Real}
> > >
> > > x::T
> > > y::T
> > >
> > > Point(x::T, y::T) = new(x,y)end
> > >
> > > thanks
>
>
