Actually there were some bugs in the code. The following code works:
zero_mask!{T,N}(a::AbstractArray{T,N}, mask::AbstractArray{Bool,N}) =
setindex!(a, zero(T), find(!mask))
function do_stuff{N}(rows, columns, mask::Nullable{Array{Bool,N}})
a = rand(rows, columns)
isnull(mask) ? nothing : zero_mask!(a, get(mask))
a
end
do_stuff(rows, columns, mask::Array{Bool}) = do_stuff(rows, columns,
Nullable(mask))
do_stuff(rows, columns) = do_stuff(rows, columns, Nullable{Array{Bool}}())
However, replacing Array with AbstractArray does not.
On Tuesday, March 31, 2015 at 1:23:44 PM UTC+13, Steve Cordwell wrote:
>
> Say I want to be able to set the value of an array to zero where a boolean
> mask array is false, then I can define this function:
>
> zero_mask!(a::AbstractArray, mask::AbstractArray{Bool}) = setindex!(a,
> zero(T), find(!mask))
>
> I have a function that constructs arrays and part of its job is to call
> zero_mask! if a mask is passed to it. I thought I could use Nullable types
> so that there is only one implementation rather than two and have helper
> methods call the do_stuff with the correct arguments.
>
> function do_stuff(rows, columns, mask::Nullable{AbstractArray{Bool}})
> a = rand(rows, columns)
> isnull(mask) ? nothing : zero_mask!(a)
> a
> end
>
> It would be nice to use do_stuff with just a boolean array, rather than
> specifying it to be Nullable.
>
> do_stuff(rows, columns, mask::AbstractArray{Bool}) = do_stuff(rows,
> columns, Nullable(mask))
>
> do_stuff(rows, columns) = do_stuff(rows, columns,
> Nullable{AbstractArray{Bool}}())
>
> However, I get the following error:
>
> do_stuff(10, 3, rand(Bool, 10, 3))
> ERROR: MethodError: `do_stuff` has no method matching
> do_stuff(::Int64, ::Int64, ::Nullable{Array{Bool,2}})
>
> Presumably because I need to define do_study{N}(rows, columns,
> Nullable{Array{Bool,N}}). Is there a way to use Nullable abstract types?
>
> Cheers
>
