Procedure

     LX4SGN (Scan for signed integer)

     SUBROUTINE LX4SGN ( STRING, FIRST, LAST, NCHAR )

Abstract

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

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 signed integer
     NCHAR      O   number of characters in the signed integer.

Detailed_Input

     STRING   is any character string.

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

Detailed_Output

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

     NCHAR    is the number of characters in the signed integer
              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 signed integer
         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 signed integer that begins on the input character FIRST. Note
     that all unsigned integers are included in the list of signed
     integers. The signed integers may in addition have a leading
     plus ('+') or minus ('-') sign.

Examples

     Suppose you believe that a string has the form

        X%Y%Z

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

     FIRST = 1
     I     = 0

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

        CALL LX4SGN ( 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)