Procedure

     LX4NUM (Scan for a number)

     SUBROUTINE LX4NUM ( STRING, FIRST, LAST, NCHAR )

Abstract

     Scan a string from a specified starting position for the
     end of a number.

Required_Reading

     None.

Keywords

     PARSING

Declarations

     IMPLICIT NONE

     CHARACTER*(*)         STRING
     INTEGER               FIRST
     INTEGER               LAST
     INTEGER               NCHAR

Brief_I/O

     VARIABLE  I/O  DESCRIPTION
     --------  ---  --------------------------------------------------
     STRING     I   any character string
     FIRST      I   first character to scan from in STRING
     LAST       O   last character that is part of a number
     NCHAR      O   number of characters in the number.

Detailed_Input

     STRING   is any character string.

     FIRST    is the location in the string to beginning scanning
              for a  number. It is assumed that the number begins
              at FIRST.

Detailed_Output

     LAST     is the last character at or after FIRST such that
              the substring STRING(FIRST:LAST) is a number.
              If there is no such substring, LAST will be returned
              with the value FIRST-1.

     NCHAR    is the number of characters in the number
              that begins at FIRST and ends at last. If there
              is no such string NCHAR will be given the value 0.

Parameters

     None.

Exceptions

     Error free.

     1)  If FIRST is beyond either end of the string, then LAST will be
         returned with the value FIRST-1 and NCHAR will be returned
         with the value 0.

     2)  If STRING(FIRST:FIRST) is not part of a number
         then LAST will be returned with the value FIRST-1 and NCHAR
         will be returned with the value 0.

Files

     None.

Particulars

     This routine allows you to scan forward in a string to locate
     a number that begins on the input character FIRST. Note
     that all decimal numbers are included in the list of numbers.
     The main difference between decimal numbers and numbers is that
     numbers may have an exponential expression attached (i.e. the
     exponent character 'e','E','d' or 'D' followed by an signed
     integer).

Examples

     Suppose you believe that a string has the form

        X%Y%Z

     where X, Y, and Z are decimal numbers of some unknown
     length and % stands for some non-numeric character. You could
     use this routine to locate the numbers in the
     string as shown below. We'll keep track of the beginning and
     ending of the numbers in the integer arrays B and E.

     FIRST = 1
     I     = 0

     DO WHILE ( FIRST .LT. LEN(STRING) )

        CALL LX4NUM ( STRING, FIRST, LAST, NCHAR )

        IF ( NCHAR .GT. 0 ) THEN

           I     = I    + 1
           B(I)  = FIRST
           E(I)  = LAST
           FIRST = LAST + 2

        ELSE

           FIRST = FIRST + 1

        END IF

     END DO

Restrictions

     None.

Literature_References

     None.

Author_and_Institution

     J. Diaz del Rio    (ODC Space)
     W.L. Taber         (JPL)

Version

    SPICELIB Version 1.1.0, 04-AUG-2021 (JDR)

        Added IMPLICIT NONE statement.

        Edited the header to comply with NAIF standard.

        Fixed return value for LAST in $Exceptions section entry #1.

    SPICELIB Version 1.0.0, 12-JUL-1994 (WLT)