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Inside Macintosh: Text /

Chapter 5 - Text Utilities / Text Utilities Reference

Routines / Determining Sorting Order for Strings in the Same Language

RelString

The RelString function compares two Pascal strings using the string comparison rules of the Macintosh file system and returns a value that indicates the sorting order of the first string relative to the second string. This function does not make use of any script or language information; it assumes the original Macintosh character set only. RelString uses the sorting rules that are described in Table 5-2 on page 5-17.

FUNCTION RelString (aStr, bStr: Str255;
                    caseSens, diacSens: Boolean): Integer;

aStr

One of the Pascal strings to be compared.

bStr

The other Pascal string to be compared.

caseSens

A flag that indicates how to handle case-sensitive information during the comparison. If the value of caseSens is TRUE, uppercase characters are distinguished from the corresponding lowercase characters. If it is FALSE, case information is ignored.

diacSens

A flag that indicates how to handle information about diacritical marks during the string comparison. If the value of diacSens is TRUE, characters with diacritical marks are distinguished from the corresponding characters without diacritical marks during the comparison. If it is FALSE, diacritical marks are ignored.

DESCRIPTION

RelString returns -1 if the first string is less than the second string, 0 if the two strings are equal, and 1 if the first string is greater than the second string. It compares the two strings in the same manner as does the EqualString function, by simply looking at the ASCII values of their characters. However, RelString provides more information about the two strings--it indicates their relationship to each other, rather than determining if they are exactly equal.

If the value of the diacSens parameter is FALSE, RelString ignores diacritical marks and strips them as shown in the appendix "International Resources" in this book.

If the value of the caseSens parameter is FALSE, the comparison is not case-sensitive; RelString performs a conversion from lowercase to uppercase characters.

SPECIAL CONSIDERATIONS

The RelString function is not localizable and does not work properly with non-Roman script systems.

ASSEMBLY-LANGUAGE INFORMATION

The trap macro and routine selector for the RelString function are

Trap macro	Selector
_RelString	$A050

The trap macro for the RelString function can take optional arguments, each of which changes the default setting used by the macro when it is called without arguments. Each of these arguments corresponds to the Boolean parameters that are used with the Pascal function call. The various permutations of this trap macro are shown below; you must type each exactly as it is shown. The syntax shown here applies to the MPW Assembler; if you are using another development system, be sure to consult its documentation for the proper syntax.

Macro permutation	Value of diacSens	Value of caseSens
_RelString	FALSE	FALSE
_RelString ,MARKS	TRUE	FALSE
_RelString ,CASE	FALSE	TRUE
_RelString ,MARKS,CASE	TRUE	TRUE

The registers on entry and exit for this routine are

Registers on entry
A0	pointer to first character of the first string
A1	pointer to first character of the second string
D0	high-order word: number of bytes in the first string low-order word: number of bytes in the second string

Registers on exit
D0	long word result: -1 if first string is less than second, 0 if equal, 1 if first string is greater than second