numbck.f

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C> @file
C> @author WOOLLEN @date 1994-01-06
      
C> THIS FUNCTION CHECKS THE INPUT CHARACTER STRING TO DETERMINE
C>   WHETHER IT CONTAINS A VALID FXY (DESCRIPTOR) VALUE.
C>
C> PROGRAM HISTORY LOG:
C> 1994-01-06  J. WOOLLEN -- ORIGINAL AUTHOR
C> 2003-11-04  J. ATOR    -- ADDED DOCUMENTATION
C> 2003-11-04  S. BENDER  -- ADDED REMARKS/BUFRLIB ROUTINE
C>                           INTERDEPENDENCIES
C> 2003-11-04  D. KEYSER  -- SPLIT NON-ZERO RETURN INTO -1 FOR INVALID
C>                           CHARACTER IN POSITION 1, -2 FOR INVALID
C>                           CHARACTERS IN POSITIONS 2 THROUGH 6, -3 FOR
C>                           INVALID CHARACTERS IN POSITIONS 2 AND 3 DUE
C>                           TO BEING OUT OF RANGE, AND -4 FOR INVALID
C>                           CHARACTERS IN POSITIONS 4 THROUGH 6 DUE TO
C>                           BEING OUT OF RANGE (RETURN ONLY -1 BEFORE
C>                           FOR ALL PROBLEMATIC CASES); UNIFIED/
C>                           PORTABLE FOR WRF; ADDED HISTORY
C>                           DOCUMENTATION
C> 2007-01-19  J. ATOR    -- CLEANED UP AND SIMPLIFIED LOGIC
C>
C> USAGE:   NUMBCK (NUMB)
C>   INPUT ARGUMENT LIST:
C>     NUMB     - CHARACTER*6: FXY VALUE TO BE CHECKED
C>
C>   OUTPUT ARGUMENT LIST:
C>     NUMBCK   - INTEGER: INDICATOR AS TO WHETHER NUMB IS VALID:
C>                       0 = YES
C>                      -1 = NO - first character ("F" value) is not '0',
C>                           '1', '2' OR '3'
C>                      -2 = NO - remaining characters (2-6) ("X" and "Y"
C>                           values) are not all numeric
C>                      -3 = NO - characters 2-3 ("X" value) are not
C>                           between '00' and '63'
C>                      -4 = NO - characters 4-6 ("Y" value) are not
C>                           between '000' and '255'
C>
C> REMARKS:
C>    THIS ROUTINE CALLS:        DIGIT
C>    THIS ROUTINE IS CALLED BY: IGETFXY  RDUSDX
C>                               Normally not called by any application
C>                               programs.
C>
      FUNCTION numbck(NUMB)



      CHARACTER*6  numb
      LOGICAL      digit

C-----------------------------------------------------------------------
C-----------------------------------------------------------------------

C  CHECK THE FIRST CHARACTER OF NUMB
C  ---------------------------------

      IF( llt(numb(1:1),'0') .OR. lgt(numb(1:1),'3') ) THEN
         numbck = -1
         RETURN
      ENDIF

C  CHECK FOR A VALID DESCRIPTOR
C  ----------------------------

      IF(digit(numb(2:6))) THEN
         READ(numb,'(1X,I2,I3)') ix,iy
      ELSE
         numbck = -2
         RETURN
      ENDIF

      IF(ix.LT.0 .OR. ix.GT. 63) THEN
         numbck = -3
         RETURN
      ELSE IF(iy.LT.0 .OR. iy.GT.255) THEN
         numbck = -4
         RETURN
      ENDIF

      numbck = 0

      RETURN
      END