The GNU Fortran Compiler: PRESENT

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### 8.195 `PRESENT` — Determine whether an optional dummy argument is specified

Description:

  Determines whether an optional dummy argument is present.

Standard:

  Fortran 95 and later

Class:

  Inquiry function

Syntax:

  `RESULT = PRESENT(A)`

Arguments:

  A | May be of any type and may be a pointer, scalar or array value, or a dummy procedure. It shall be the name of an optional dummy argument accessible within the current subroutine or function.

Return value:

  Returns either `TRUE` if the optional argument A is present, or `FALSE` otherwise.

Example:

      PROGRAM test_present
        WRITE(*,*) f(), f(42)      ! "F T"
      CONTAINS
        LOGICAL FUNCTION f(x)
          INTEGER, INTENT(IN), OPTIONAL :: x
          f = PRESENT(x)
        END FUNCTION
      END PROGRAM