[julia-users] Passing a function outputted by a higher order function to C - function not yet c-callable

[Michael Lindon]

I have function baz which outputs the product of the input at 2:

function baz{T}(x::T)
        return convert(Cdouble,x*2)::Cdouble
end

I want to use this function in some C function that I am calling. Running

julia> myptr=cfunction(baz,Cdouble,(Ref{Cdouble}))
Ptr{Void} @0x00007f2623c9c1d0

is fine, and I can proceed to  pass the function pointer to my C function.




Say I want the product of the input and another integer. I have a higher 
order function bar

function bar(y)
        function foo{T}(x::T)
                return convert(Cdouble,x*y)::Cdouble
        end
end

now I can get the baz function like this

julia> foo=bar(2)
foo (generic function with 1 method)

foo has the same method as baz, and the same functionality, but cfunction 
results in an error:

julia> myptr=cfunction(foo,Cdouble,(Ref{Cdouble}))
ERROR: cfunction: no method exactly matched the required type signature 
(function not yet c-callable)
 in cfunction at c.jl:9


:(


How can I pass the function pointers of the outputs of my higher order 
function bar to my C function?