REAL array(2,2,2,2,2,2,2,2,2,2,2,2,2,2,2)declares a 15-dimensional array.
REAL,PARAMETER :: idmat3(*,*) = Reshape( [ 1,0,0,0,1,0,0,0,1 ], [ 3,3 ] ) REAL,PARAMETER :: yeardata(2000:*) = [ 1,2,3,4,5,6,7,8,9 ]declares idmat3 to have the bounds (1:3,1:3), and yeardata to have the bounds (2000:2008).
TYPE(REAL) x TYPE(COMPLEX(KIND(0d0))) y TYPE(CHARACTER(LEN=80)) zis completely equivalent, apart from being more confusing, to
REAL x COMPLEX(KIND(0d0)) y CHARACTER(LEN=80) z
PROCEDURE,NOPASS :: a PROCEDURE,NOPASS :: b=>x PROCEDURE,NOPASS :: cthe single statement
PROCEDURE,NOPASS :: a, b=>x, cwill suffice.
INTEGER workspace(MERGE(10,20,C_ASSOCIATED(X,C_LOC(Y))))is allowed, and will give workspace a size of 10 elements if the C pointer X is associated with Y, and 20 elements otherwise.
INTERFACE OPERATOR(.user.) PURE INTEGER FUNCTION userfun(x) REAL,INTENT(IN) :: x END FUNCTION END INTERFACEthe user-defined operator .user. may be used in a specification expression as follows:
LOGICAL mask(.user.(3.145))
Note that this applies to overloaded intrinsic operators as well as user-defined operators.
Type t2 Type(t),Pointer :: p Type(t),Allocatable :: a End Type Type t Integer c End Type
An allocatable component can also be of recursive type, or two types can be mutually recursive. For example,
Type t Integer v Type(t),Allocatable :: a End TypeThis allows lists and trees to be built using allocatable components. Building or traversing such data structures will usually require recursive procedure calls, as there is no allocatable analogue of pointer assignment.
No matter how deeply nested such recursive data structures become, they can never be circular (again, because there is no pointer assignment). As usual, deallocating the top object of such a structure will recursively deallocate all its allocatable components.
For example, in
Elemental Subroutine s(x,n,y) Real,Intent(In) :: x Integer,Intent(In) :: n Real,Intent(Out) :: y Real temp(n) ...the dummy argument N can be used to declare the local array TEMP.
For example,
Module m Real,Target :: x Real,Pointer :: p => x End Module Program test Use m p = 3 Print *,x ! Will print the value 3.0 End Program
For example,
Module m Real,Target :: x Type t Real,Pointer :: p => x End Type End Module Program test Use m Type(t) y y%p = 3 Print *,x ! Will print the value 3.0 End Program
For example,
Module m Real,Target :: x Type t Real,Pointer :: p End Type End Module Program test Use m Type(t) :: y = t(x) y%p = 3 Print *,x ! Will print the value 3.0 End Program
For example, with this module,
Module m Real,Target,Save :: table(100) = 0 Contains Function f(n) Integer,Intent(In) :: n Real,Pointer :: f f => table(Min(Max(1,n),Size(table))) End Function End Modulethe program below will print “-1.23E+02”.
Program example Use m f(13) = -123 Print 1,f(13) 1 Format(ES10.3) End Program
It should be noted that the syntax of a statement function definition is identical to part of the syntax of a pointer function reference as a variable; the existence of a pointer-valued function that is accessible in the scope determines which of these it is. This may lead to confusing error messages in some situations.
With the above module, this program demonstrates the use of the feature with an ASSOCIATE construct.
Program assoc_eg Use m Associate(x=>f(3), y=>f(4)) x = 0.5 y = 3/x End Associate Print 1,table(3:4) ! Will print " 5.00E-01 6.00E+00" 1 Format(2ES10.2) End Program
Finally, here is an example using argument passing.
Program argument_eg Use m Call set(f(7)) Print 1,table(7) ! Will print "1.41421" 1 Format(F7.5) Contains Subroutine set(x) Real,Intent(Out) :: x x = Sqrt(2.0) End Subroutine End Program
Other contexts where a reference to a pointer-valued function may be used instead of a variable designator include:
Module ppfun Private Abstract Interface Subroutine charsub(string) Character(*),Intent(In) :: string End Subroutine End Interface Public charsub,hello_goodbye Contains Subroutine hello(string) Character(*),Intent(In) :: string Print *,'Hello: ',string End Subroutine Subroutine bye(string) Character(*),Intent(In) :: string Print *,'Goodbye: ',string Stop End Subroutine Function hello_goodbye(flag) Logical,Intent(In) :: flag Procedure(hello),Pointer :: hello_goodbye If (flag) Then hello_goodbye => hello Else hello_goodbye => bye End If End Function End Module Program example Use ppfun Procedure(charsub),Pointer :: pp pp => hello_goodbye(.True.) Call pp('One') pp => hello_goodbye(.False.) Call pp('Two') End ProgramThe function hello_goodbye in module ppfun returns a pointer to a procedure, which needs to be pointer-assigned to a procedure pointer to be invoked. When executed, this example will print
Hello: One Goodbye: Two
Use of this feature is not recommended, as it blurs the lines between data objects and procedures; this may lead to confusion or misunderstandings during code maintenance. The feature provides no functionality that was not already provided by procedure pointer components.