PRESENT(A)

Purpose

Determine whether an optional argument is present. If it is not present, you may only pass it as an optional argument to another procedure or pass it as an argument to PRESENT.

Class

Inquiry function

Argument type and attributes

A: An INTENT(IN) argument. The actual argument corresponding to A is an optional dummy argument that is accessible in the procedure in which the PRESENT function reference appears.

Result type and attributes

Default logical scalar.

Result value

The result is .TRUE. if the actual argument is present (that is, if it was passed to the current procedure in the specified dummy argument), and .FALSE. otherwise.

Examples

      SUBROUTINE SUB (X, Y)
        REAL, OPTIONAL :: Y
        IF (PRESENT (Y)) THEN
! In this section, we can use y like any other variable.
           X = X + Y
           PRINT *, SQRT(Y)
        ELSE
! In this section, we cannot define or reference y.
           X = X + 5
! We can pass it to another procedure, but only if
! sub2 declares the corresponding argument as optional.
           CALL SUB2 (Z, Y)
        ENDIF
      END SUBROUTINE SUB

Related information

OPTIONAL