In Fortran, when in extension definition, how to set a public procedure into private?

问题

Assume I first defined a type A in which a public procedure f is defined, and may also be bonded to A. In another module I have this type extended into B. However, when I use type B, I do not want f to be exposed. By the way, I don't want to use the submod technique.

complement:

Assume type(A) is already defined:

module mA 
type::A
 ...
 contains 
 procedure::f
endtype
endmodule

In another module B, we extend A as:

module mB 
use mA
type,extends(A)::B
 ...
endtype
endmodule

In this module, f may still be used. However, next, in module mC I will use(declare)

type(B)::Ob 

and I wish "call Ob%f()" to be illegal. Or equivalently speaking, I want to ban some of the function when I extend a class.

回答1:

It is hard to understand your descriiption, but if I understand it correctly it is not possible.

Consider you have a variable class(A) :: o. You are allowed to call

call o%f()

class(A) is polymorphic and can be any extended type of A so its dynamic type can be type(B). So B MUST provide publicly accessible procedure f to stay compatible with the parent.

来源：https://stackoverflow.com/questions/47959048/in-fortran-when-in-extension-definition-how-to-set-a-public-procedure-into-pri