Procedure

     EQCHR (Equivalent characters)

     LOGICAL FUNCTION EQCHR ( A, B )

Abstract

     Return .TRUE. if two given characters are equivalent when the
     case of the characters is ignored.

Required_Reading

     None.

Keywords

     CHARACTER

Declarations

     IMPLICIT NONE

     CHARACTER*(1)         A
     CHARACTER*(1)         B

Brief_I/O

     VARIABLE  I/O  DESCRIPTION
     --------  ---  --------------------------------------------------
     A          I   one of the characters to check
     B          I   the other character to check

     The function returns .TRUE. if the characters are equivalent

Detailed_Input

     A,
     B        are two characters that are to be compared to see
              if they are the same letter (although possibly
              having different case such as 'a' and 'A')

Detailed_Output

     The function returns the value .TRUE. if the two input characters
     are the same or can be made the same by converting both to
     upper or lower case.

Parameters

     None.

Exceptions

     Error free.

Files

     None.

Particulars

     This is a utility routine for comparing two characters to
     see if they are the same when converted to upper case. It
     is particularly useful when writing string analysis routines
     that should be case insensitive. Instead of writing the
     expression

        A .EQ. B

     use the expression

        EQCHR ( A, B )

     in all tests of equivalence for characters.

Examples

     Suppose you want to determine whether or not two strings
     are the same if differences in the case of letters are ignored.
     The following code fragment shows how you can use this routine
     to check for the equivalence of character strings.

        MORE  = .TRUE.
        SAME  = .TRUE.
        L1    =  LEN(STR1)
        L2    =  LEN(STR2)
        CHECK = MIN ( L1, L2 )

        DO WHILE ( SAME .AND. MORE )

           SAME = EQCHR( STR1(I:I), STR2(I:I) )
           I    = I + 1
           MORE = I .LT. CHECK

        END DO

        IF ( .NOT. SAME ) THEN

           There's nothing to do, we already know the strings
           are not the same.

        ELSE IF ( L1 .LT. L2 ) THEN

           The only way the strings can be regarded as being equal
           is if the extra unchecked characters in STR2 are all blank.

           SAME = STR2(I:) .EQ. ' '

        ELSE

           Same test as previous one but with STR1 this time.

           SAME = STR1(I:) .EQ. ' '

        END IF

Restrictions

     None.

Literature_References

     None.

Author_and_Institution

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

Version

    SPICELIB Version 2.0.1, 26-OCT-2021 (JDR)

        Edited the header to comply with NAIF standard.

    SPICELIB Version 2.0.0, 17-SEP-1998 (EDW)

        Replace the UVALUE data statement with a loop to fill
        UVALUE. The Absoft Mac compiler failed to compile the
        data statement correctly, and so this function failed
        to work properly in all situations on the Mac. The
        corrects the problem and functions on all platforms.

    SPICELIB Version 1.0.0, 16-MAY-1995 (WLT)