pkftbv.f

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C> @file
C> @brief Determine the numerical data value equivalent to the
C> setting of a specified bit within a flag table.
C>
C> @author J. Ator @date 2005-11-29
 
C> This function computes the numerical value equivalent to the
C> setting of bit #(IBIT) within a flag table of NBITS bits.
C>
C> If the computation fails for any reason, then the function
C> returns the current placeholder value for "missing" data.
C>
C> @param[in] NBITS -- integer: Total number of bits in flag table
C> @param[in] IBIT  -- integer: Number of bit to be set
C>
C> @returns pkftbv  -- real*8: Value equivalent to the setting of
C>                     bit #(IBIT) within a flag table of NBITS bits
C>
C> @remarks
C> - This function is the logical inverse of subroutine upftbv().
C> - According to the WMO standard, bits within a bit field are
C> numbered from left to right, so bit #1 is always the high-order
C> (i.e. most significant) bit in any bit field.
C>
C> @author J. Ator @date 2005-11-29
      RECURSIVE FUNCTION pkftbv(NBITS,IBIT) RESULT(R8VAL)
 
      USE modv_bmiss
      USE modv_im8b
 
      real*8 r8val
 
C----------------------------------------------------------------------
C----------------------------------------------------------------------
 
C     Check for I8 integers.
 
      IF(im8b) THEN
         im8b=.false.
 
         CALL x84(nbits,my_nbits,1)
         CALL x84(ibit,my_ibit,1)
         r8val=pkftbv(my_nbits,my_ibit)
 
         im8b=.true.
         RETURN
      ENDIF
 
      IF((nbits.LE.0).OR.(ibit.LE.0).OR.(ibit.GT.nbits)) THEN
          r8val = bmiss
      ELSE
          r8val = (2.)**(nbits-ibit)
      ENDIF
 
      RETURN
      END