Why i can not call returned method directly

Question

I have the following curious case in Erlang:

Tx=fun(A)->G=fun()->A+33 end,G end.

I do not understand why i can't call the returned method directly , and need to store it in a variable first:

Tx(3)().   ->  1: syntax error before: '(' //why does this not work ?

Var=Tx(3)     //and this
Var()         // works

I can not call a method that is returned ?

Answer 1

Wrap the returned fun into brackets:

(Tx(3))().

Answer 2

It's an order of operations problem. The compiler/runtime doesn't understand what's being returned from Tx(3) is a function. By adding () around it (Tx(3)), Tx(3) is evaluated first, is seen as a function, and can then be evaluated again.

Answer 3

this is a high order function(like closure)

Tx= fun(A)->
      G=fun()->A+33 end,
     G 
    end.

Tx is a function where arity = 1, and return a function called G

and

G with arity = 0