Sheehan, are you planning on doing a lot of operations with empty arrays?
On 0.5 with your example
julia> [Foo(1), Foo(2)] + [Foo(1), Foo(0)]
2-element Array{Foo,1}:
Foo{Float64}(1.0)
Foo{Int64}(1)
The problem is empty arrays, when the type cannot be inferred broadcast
uses the types of each element to build the array. When there are no
elements it doesn't know what type to choose.
On Friday, September 23, 2016 at 11:47:11 PM UTC+2, Sheehan Olver wrote:
>
> OK, here's a better example of the issue: in the following code I would
> want it to return an *Array(Foo,0)*, not an *Array(Any,0). *Is this
> possible without overriding promote_op?
>
> *julia> **immutable Foo{T}*
>
> *x::T*
>
> *end*
>
>
> *julia> **import Base.+*
>
>
> *julia> **+(a::Foo,b::Foo) = (a.x==b.x? Foo(1.0) : Foo(1))*
>
> *+ (generic function with 164 methods)*
>
>
> *julia> **Array(Foo{Float64},0)+Array(Foo{Float64},0)*
>
> *0-element Array{Any,1}*
>
>
>
>
>
> On Friday, September 23, 2016 at 10:54:03 PM UTC+10, Pablo Zubieta wrote:
>>
>> In julia 0.5 the following should work without needing doing anything to
>> promote_op
>>
>> import Base.+
>> immutable Foo end
>> +(a::Foo, b::Foo) =1.0
>> Array{Foo}(0) + Array{Foo}(0))
>>
>> promote_op is supposed to be an internal method that you wouldn't need to
>> override. If it is not working i because the operation you are doing is
>> most likely not type stable. So instead of specializing it you could try to
>> remove any type instabilities in the method definitions over your types.
>>
>> On Friday, September 23, 2016 at 5:35:05 AM UTC+2, Sheehan Olver wrote:
>>>
>>>
>>> The subject says it all: it looks like one can override promote_op to
>>> support the following behaviour:
>>>
>>> *julia> **import Base.+*
>>>
>>>
>>> *julia> **immutable Foo end*
>>>
>>> WARNING: Method definition (::Type{Main.Foo})() in module Main at
>>> REPL[5]:1 overwritten at REPL[10]:1.
>>>
>>>
>>> *julia> **+(a::Foo,b::Foo) = 1.0*
>>>
>>> *+ (generic function with 164 methods)*
>>>
>>>
>>> *julia> **Base.promote_op(::typeof(+),::Type{Foo},::Type{Foo}) =
>>> Float64*
>>>
>>>
>>> *julia> **Array(Foo,0) + Array(Foo,0)*
>>>
>>> *0-element Array{Float64,1}*
>>>
>>>
>>> Is this documented somewhere? What if we want to override /, -, etc.,
>>> is the solution to write a promote_op for each case?
>>>
>>
