[julia-users] Why can't function passing be unrolled?

[Bryan Rivera]

Why can't this:

function functionWithPaths(state::State, a::Int, b::Int, onPathA)
 if( a > b)
     onPathA(a, b)

     state.value = a
 else
     state.value = a + b
 end
end


function test()

   array = zeros(Int, 100)

   onPathA(a, b) = array[a] = b

   functionWithPaths(State(0), 10, 20, onPathA)

end


Be unrolled to this:

function unrolled_functionWithPaths(state::State, a::Int, b::Int, array) # 
`array` injected
   if( a > b)
       array[a] = b # Injected function

       state.value = a
   else
       state.value = a + b
   end
end


I tried to keep it simple here - this is not the exact use case, but it is 
exactly what I want.

However, I tried using anonymous functions, both Julia's and FastAnonymous' 
, and they both have issues in my more complex use case.

The best route, as far as I can tell, is to create a macro.  I tried a few 
ways and got stuck.  

Maybe someone can create it with less effort?  I have the feeling this 
would be *very* useful.