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

   None. 

   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. 

   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.  

               The normal range of first is 0 : strlen(string)-1.

   last        is the last character at or after first such that the
               substring ranging from string[first] through
               string[last] is a signed integer.  If there is no such
               substring, last will be returned with the value first-1.

               If a signed integer is found, last will be in the
               range is 0 : strlen(string)-1.


   nchar       is the number of characters in the signed integer that
               begins at index first and ends at last.  If there is no
               such string nchar will be given the value 0.

   None. 

   This routine allows you to scan forward in a string to locate a
   signed integer that begins on the input character at index 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.

   1) 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 any character that cannot occur in a signed integer.
      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.


         #include <string.h>
         #include "SpiceUsr.h"

               .
               .
               .

         first = 0;
         i     = 0;
         len   = strlen(string);

         while ( first < len-1 )
         {
            lx4sgn_c ( string, first, &last, &nchar );

            if ( nchar > 0 )
            {
               i++;

               b[i]  = first;
               e[i]  = last;
               first = last  +  2;
            }
            else
            {
               first++;  
            }
         }

   None. 

   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] 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. 

   3) If the input string pointer is null, the error SPICE(NULLPOINTER)
      will be signaled.

   4) If the input string has length zero, last will be set to first-1
      and nchar will be set to zero.  This case is not considered an
      error.

   None. 

   N.J. Bachman    (JPL)
   W.L. Taber      (JPL) 

   None. 

   -CSPICE Version 1.0.0, 18-AUG-2002 (NJB) (WLT)

   Scan a string for a signed integer.