Fortran Usage of Modules Access control
Example
Accessibility of symbols declared in a module can be controlled using private and public attributes and statement.
Syntax of the statement form:
!all symbols declared in the module are private by default
private
!all symbols declared in the module are public by default
public
!symbols in the list will be private
private :: name1, name2
!symbols in the list will be public
public :: name3, name4
Syntax of the attribute form:
integer, parameter, public :: maxn = 1000
real, parameter, private :: local_constant = 42.24
Public symbols can be accessed from program units using the module, but private symbols cannot.
When no specification is used, the default is public.
The default access specification using
private
or
public
can be changed by specifying different access with entity-declaration-list
public :: name1, name2
or using attributes.
This access control also affects symbols imported from another module:
module mod1
integer :: var1
end module
module mod2
use mod1, only: var1
public
end module
program test
use mod2, only: var1
end program
is possible, but
module mod1
integer :: var1
end module
module mod2
use mod1, only: var1
public
private :: var1
end module
program test
use mod2, only: var1
end program
is not possible because var is private in mod2.
