Procedure

     SAMCH ( Same character )

     LOGICAL FUNCTION SAMCH ( STR1, L1, STR2, L2 )

Abstract

     Determine if two characters from different strings are the
     same.

Required_Reading

     None.

Keywords

     UTILITY

Declarations

     IMPLICIT NONE

     CHARACTER*(*)         STR1
     INTEGER               L1
     CHARACTER*(*)         STR2
     INTEGER               L2

Brief_I/O

     VARIABLE  I/O  DESCRIPTION
     --------  ---  --------------------------------------------------
     STR1       I   A character string
     L1         I   The location (index) of a character in STR1
     STR2       I   A character string
     L2         I   The location (index) of a character in STR2

     The function returns .TRUE. if the two characters are the
     same.

Detailed_Input

     STR1     is a character string

     L1       is the location (index) of a character in STR1

     STR2     is a character string

     L2       is the location (index) of a character in STR2

Detailed_Output

     The function returns .TRUE. if the characters STR1(L1:L1) and
     STR2(L2:L2) are the same.

     If the characters are different or L1 or L2 is out of range the
     function returns .FALSE.

Parameters

     None.

Exceptions

     Error free.

     1)  If either L1 or L2 is out of range the function returns
         .FALSE.

Files

     None.

Particulars

     This is a utility function for determining whether or not
     two characters in different strings are the same. This
     function is intended for situation in which you need to
     search two strings for a match (or mismatch).

Examples

     Often you need to scan through two string comparing character
     by character until a mismatch occurs. The usual way to code
     this is

        DO WHILE (        L1 .LE. LEN(STR1)
                    .AND. L2 .LE. LEN(STR2)
                    .AND. STR1(L1:L1) .EQ. STR2(L2:L2) )

           L1 = L1 + 1
           L2 = L2 + 1

        END DO

        Check L1, L2 to make sure we are still in range, etc.

     The problem with this loop is that even though the check to make
     sure that L1 and L2 are in range is performed, FORTRAN may
     go ahead and compute the equality condition even though one of the
     first two steps failed. This can lead to out of range errors
     and possible halting of your program depending upon how
     the routine is compiled. An alternative way to code this is

        IF ( L1 .LE. LEN(STR1) .AND. L2 .LE. LEN(STR2) ) THEN
           ALIKE = STR1(L1:L1) .EQ. STR2(L2:L2)
        ELSE
           ALIKE = .FALSE.
        END IF

        DO WHILE ( ALIKE )

           L1 = L1 + 1
           L2 = L2 + 1

           IF ( L1 .LE. LEN(STR1) .AND. L2 .LE. LEN(STR2) ) THEN
              ALIKE = STR1(L1:L1) .EQ. STR2(L2:L2)
           ELSE
              ALIKE = .FALSE.
           END IF
        END DO

     However this is a much more complicated section of code. This
     routine allows you to code the above loops as:


        DO WHILE ( SAMCH ( STR1,L1, STR2,L2 )  )
           L1 = L1 + 1
           L2 = L2 + 1
        END DO

     The boundary checks are automatically performed and out
     of range errors are avoided.

Restrictions

     None.

Literature_References

     None.

Author_and_Institution

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

Version

    SPICELIB Version 1.0.1, 12-AUG-2021 (JDR)

        Edited the header to comply with NAIF standard.

    SPICELIB Version 1.0.0, 31-MAR-1995 (WLT)