On Sat, Jan 9, 2016 at 1:48 PM, Alexandr <updates...@gmail.com> wrote:
> I am using Version 0.4.0 (2015-10-08 06:20 UTC)
>
> I restarted Julia repl/intrpreter.
>
> Below is a complete code where I am trying to solve my task in a two ways:
>
> 1) by defining a Union of the types
>
> 2) by specifying the type of elements in the input vector as "Number".
> (Is it correct to do it?)
> Because according to the types hierarchy here:
> https://en.wikibooks.org/wiki/Introducing_Julia/Types
> both Int and Float are subtypes of super type Number and Real.
>
> #------------------------------------#
> IntOrFloat = Union{Int, AbstractFloat}
>
> function ff1(v::Array{IntOrFloat,1})
> mean(v)
> end
> println( ff1([1.0, 2.0]) )
>
> function ff2(v::Vector{IntOrFloat})
> mean(v)
> end
> println( ff2([1.0, 2.0]) )
>
> function ff3(v::Vector{Number})
> filter(x-> x>=1.5, v)
> end
> ff3([1.0, 2.0, 3.0, 5.0])
>
> #------------------------------------#
> Output errors:
>
> ERROR: LoadError: MethodError: `ff1` has no method matching
> ff1(::Array{Float64,1})
>
> ERROR: LoadError: MethodError: `ff2` has no method matching
> ff2(::Array{Float64,1})
>
> ERROR: LoadError: MethodError: `ff3` has no method matching
> ff3(::Array{Float64,1})
>
> #------------------------------------#
The signature of the first and second functions are exactly the same
and all three gives error as expected.
See the manual I linked. Float64 <: Number does not imply
Vector{Float64} <: Vector{Number}
>
>
> On 1/9/2016 7:32 PM, Yichao Yu wrote:
>>>
>>> Which version are you using? `f1` shouldn't match either and it's a
>>> bug if it does.
>>
>> Also check if you've already defined another `f1` that does accept the
>> arrays of different types.
>>
>> And for why neither of them should match. See
>> http://julia.readthedocs.org/en/latest/manual/types/#parametric-composite-types
>>
>>>
>>>>
>>>> --
>>>> Alexandr
>
> --
> Alexandr
