Here the function imresize from ImageTransformation.jl is defined.
On line 164 there is this expression:
resized[I] = original(I_o...)
From Julia's documentation I understood the triple dot is called splatting and it unpacks an argument into multiple arguments. For example I_o is a tuple here. My issue is that I cannot find any trace of a function called original in the mentioned Julia file.
Where is original? From the code itself I have the impression that original should be an array and indeed on line 147 the type of original is annotated as AbstractInterpolation yet in turn I could not find any object of such type in the rest of the code.
CodePudding user response：
The function declaration reads:
function imresize!(resized::AbstractArray{T,N}, original::AbstractInterpolation{S,N}) where {T,S,N}
Hence, original is the parameter of the imresize! function.
Now, you can see that this is called with paranthesis (). This happens because a functor has been defined.
This functor seems to be defined outside of this package but you can see in the package how it is used:
@inline _getindex(A, v) = A[v...]
@inline _getindex(A::AbstractInterpolation, v) = A(v...)
so simply it is used to yield an interpolation element.
You can find the actual declaration of this functor in the Interpolations package (for each interpolation type). For an example:
@inline function (itp::BSplineInterpolation)(x::Vararg{UnexpandedIndexTypes})
itp(to_indices(itp, x)...)
end