SCAN — Scan a string for the presence of a set of charactersIf BACK is either absent or equals FALSE, this function
returns the position of the leftmost character of STRING that is
in SET. If BACK equals TRUE, the rightmost position
is returned. If no character of SET is found in STRING, the
result is zero.
     
RESULT = SCAN(STRING, SET[, BACK [, KIND]])
     | STRING | Shall be of type CHARACTER. | 
| SET | Shall be of type CHARACTER. | 
| BACK | (Optional) shall be of type LOGICAL. | 
| KIND | (Optional) An INTEGERinitialization
expression indicating the kind parameter of the result. | 
INTEGER and of kind KIND. If
KIND is absent, the return value is of default integer kind.
               PROGRAM test_scan
            WRITE(*,*) SCAN("FORTRAN", "AO")          ! 2, found 'O'
            WRITE(*,*) SCAN("FORTRAN", "AO", .TRUE.)  ! 6, found 'A'
            WRITE(*,*) SCAN("FORTRAN", "C++")         ! 0, found none
          END PROGRAM