Check if a parameter of a function is a function

Question

I have a function:

function f(a)
   do something that depends on a
end

which behaviour depends on the parameter a. This can be a string, an int or a function itself. For this, I want to check if the parameter is a function itself.

function f(a)
   if typeof(a) == int
      ...
   end
   ...
end

I tried to use typeof(a). If a is a function, I get :

typeof(a) (singleton type of function a, subtype of Function)

but if I then use:

typeof(a) == Function

it is false.

Answer 1

You might also consider using Julia's Multiple Dispatch feature:

function f(x::Function)
  # do something with a Function
end

funcion f(x::Int)
  # do something with an Int
end

instead of using conditions inside the function.

This has the benefit of being faster if the compiler can do the type inference during compile-time and being more Julian.

Answer 2

You can use isa() for this. A simple example:

julia> f(x) = x
f (generic function with 1 method)

julia> isa(f, Function)
true

isa can also be used as an infix operator:

julia> f isa Function
true