VMS Help FORTRAN, Statements, Directive Statements, ASSERT  *Conan The Librarian (sorry for the slow response - running on an old VAX)

  CDEC$ ASSERT (log-exp)

  or in statement form:

  ASSERT (log-exp)

  log-exp  Is a logical expression.

  The ASSERT directive (also available in statement form) provides
  the compiler with information to improve optimization (particularly
  if vectorization or automatic decomposition for parallel processing
  is being performed).  The directive can also be used to provide a
  form of error checking in user applications.

  The ASSERT directive tells the compiler that "log-exp" evaluates as
  .TRUE.  at the location in the program unit where the ASSERT
  appears.

  If the compiler option /CHECK=ASSERTIONS (or
  OPTIONS/CHECK=ASSERTIONS) is in effect, the compiler adds run-time
  code to verify the asserted expression; if the expression evaluates
  as .FALSE., a run-time error is signaled.

  The following is an example of how to use the CDEC$ ASSERT
  directive for error checking (the program is compiled using the
  compiler option /CHECK=ASSERTIONS:

  CDEC$ ASSERT (ICOUNT .NE. 0)
        IVAL = IVAL / ICOUNT      ! Avoid zero-divide exception