Suppose I have a pointer to a polymorphic object:

TYPE, ABSTRACT:: ab
ENT TYPE

TYPE, EXTENDS(ab):: co
  INTEGER:: i
ENT TYPE

Class(ab), POINTER:: foo

How do I initialize the object pointed by foo to be a co object, in the executable part of the code? I am thinking of something like

foo => co(1)  ! WRONG

but this is wrong.

CodePudding user response：

Pointers can only be initialized with a target with the save attribute or with null(). If you mean the initialization during compilation in the declaration part.

In the executable part of code you can certainly make the pointer to point to an object. But you need an actual object with the target attribute or you need to make an anonymous target using the allocate() statement.

co(1) is an expression or a value result of an expression. You cannot point to it, it does not have the pointer attribute. You could allocate an anonymous target with this value

allocate(foo, source=co(1))

Consider using allocatable instead of a pointer, they should be strongly preferred. If you could use allocatable, it is as simple as

foo = co(1)

thanks to the automatic (re)allocation in the assignment.