INTENT

Statement and Attribute: Specifies the intended use of one or more dummy arguments.

The INTENT attribute can be specified in a type declaration statement or an INTENT statement, and takes one of the following forms:

Syntax

Type Declaration Statement:

type, [att-ls,] INTENT (intent-spec) [, att-ls] :: d-arg [, d-arg] ...

Statement:

INTENT (intent-spec) [::] d-arg [, d-arg] ...

type
Is a data type specifier.

att-ls
Is an optional list of attribute specifiers.

intent-spec
Is one of the following specifiers:

• IN
  
  Specifies that the dummy argument will be used only to provide data to the procedure. The dummy argument must not be redefined (or become undefined) during execution of the procedure.
  Any associated actual argument must be an expression.
  
  
• OUT
  
  Specifies that the dummy argument will be used to pass data from the procedure back to the calling program. The dummy argument is undefined on entry and must be defined before it is referenced in the procedure.
  Any associated actual argument must be definable.
  
  
• INOUT
  
  Specifies that the dummy argument can both provide data to the procedure and return data to the calling program.
  Any associated actual argument must be definable.

d-arg
Is the name of a dummy argument or dummy pointer. It cannot be a dummy procedure.

Description

The INTENT statement can only appear in the specification part of a subprogram or interface body.

If no INTENT attribute is specified for a dummy argument, its use is subject to the limitations of the associated actual argument.

If a function specifies a defined operator, the dummy arguments must have intent IN.

If a subroutine specifies defined assignment, the first argument must have intent OUT or INOUT, and the second argument must have intent IN.

A non-pointer dummy argument with intent IN (or a subobject of such a dummy argument) must not appear as any of the following:

• A DO variable or implied-DO variable
• The variable of an assignment statement
• The pointer-object of a pointer assignment statement
• An object or STAT variable in an ALLOCATE or DEALLOCATE statement
• An input item in a READ statement
• A variable name in a NAMELIST statement if the namelist group name appears in a NML specifier in a READ statement
• An internal file unit in a WRITE statement
• A definable variable in an INQUIRE statement
• An IOSTAT or SIZE specifier in an I/O statement
• An actual argument in a reference to a procedure with an explicit interface if the associated dummy argument has intent OUT or INOUT

INTENT on a pointer dummy argument refers to the pointer association status of the pointer and has no effect on the value of the target of the pointer.

A pointer dummy argument with intent IN (or a subobject of such a pointer argument) must not appear as any of the following:

• A pointer-object in a NULLIFY statement
• A pointer-object in a pointer assignment statement
• An object in an ALLOCATE or DEALLOCATE statement
• An actual argument in a reference to a procedure if the associated dummy argument is a pointer with the INTENT(OUT) or INTENT(INOUT) attribute.

If an actual argument is an array section with a vector subscript, it cannot be associated with a dummy array that is defined or redefined (has intent OUT or INOUT).

See Also: Argument Association, Type Declarations, Compatible attributes

Examples

The following example shows type declaration statements specifying the INTENT attribute:

SUBROUTINE TEST(I, J)
  INTEGER, INTENT(IN) :: I
  INTEGER, INTENT(OUT), DIMENSION(I) :: J

The following are examples of the INTENT statement:

SUBROUTINE TEST(A, B, X)
   INTENT(INOUT) :: A, B
   ...

SUBROUTINE CHANGE(FROM, TO)
   USE EMPLOYEE_MODULE
   TYPE(EMPLOYEE) FROM, TO
   INTENT(IN) FROM
   INTENT(OUT) TO
   ...

The following shows another example:

!Calculate value into a running average and return the average cubed.

TYPE DATA
  INTEGER count
  REAL average
END TYPE
. . .
SUBROUTINE AVERAGE(value,data1,cube_ave)
  TYPE(DATA) data1
  REAL dummy
  ! value cannot be changed, while cube_ave must be defined
  ! before it can be used. Data1 is defined when the procedure is
  ! invoked, and becomes redefined in the subroutine.
  INTENT(IN)::value; INTENT(OUT)::cube_ave
  INTENT(INOUT)::data1

  ! count number of times AVERAGE has been called on the data set
  ! being passed.
  dummy = count*average + value
  data1%count = data1%count + 1
  data1%average = dummy/data1%count
  cube_ave = data1%average**3
END SUBROUTINE