..
  Copyright 1988-2021 Free Software Foundation, Inc.
  This is part of the GCC manual.
  For copying conditions, see the GPL license file

.. _verify:

VERIFY --- Scan a string for characters not a given set
*******************************************************

.. index:: VERIFY

.. index:: string, find missing set

.. function:: VERIFY

  Verifies that all the characters in :samp:`{STRING}` belong to the set of
  characters in :samp:`{SET}`.

  :param STRING:
    Shall be of type ``CHARACTER``.

  :param SET:
    Shall be of type ``CHARACTER``.

  :param BACK:
    (Optional) shall be of type ``LOGICAL``.

  :param KIND:
    (Optional) An ``INTEGER`` initialization
    expression indicating the kind parameter of the result.

  :return:
    The return value is of type ``INTEGER`` and of kind :samp:`{KIND}`. If
    :samp:`{KIND}` is absent, the return value is of default integer kind.

  :samp:`{Standard}:`
    Fortran 90 and later, with :samp:`{KIND}` argument Fortran 2003 and later

  :samp:`{Class}:`
    Elemental function

  :samp:`{Syntax}:`

  .. code-block:: fortran

    RESULT = VERIFY(STRING, SET[, BACK [, KIND]])

  :samp:`{Example}:`

    .. code-block:: fortran

      PROGRAM test_verify
        WRITE(*,*) VERIFY("FORTRAN", "AO")           ! 1, found 'F'
        WRITE(*,*) VERIFY("FORTRAN", "FOO")          ! 3, found 'R'
        WRITE(*,*) VERIFY("FORTRAN", "C++")          ! 1, found 'F'
        WRITE(*,*) VERIFY("FORTRAN", "C++", .TRUE.)  ! 7, found 'N'
        WRITE(*,*) VERIFY("FORTRAN", "FORTRAN")      ! 0' found none
      END PROGRAM

  :samp:`{See also}:`
    SCAN, 
    INDEX intrinsic