cpp$,$ cannot include any includes besides xps$.$h $($which is this file$)$

$//$ Compare two XP strings "asciibetically."

$//$ Return a negative number if lhs comes before rhs$.$

$//$ Return a positive number if lhs comes after rhs$.$

$//$ Return zero if the two strings are equal.

int xps$\_$compare$($const char$*$ lhs$,$ const char$*$ rhs$)$;

$//$ Create a new XP string that holds the concatenation of two XP strings.

$//$ The new string should contain all the characters

$//$ from lhs followed by all the characters from rhs$.$

char$*$ xps$\_$concat$($const char$*$ lhs$,$ const char$*$ rhs$)$;

$//$ Find a substring inside another XP string.

$//$ If the substring is found, return the index of the first $($leftmost$)$ match.

$//$ If the substring is not found, return XPS$\_$NPOS $($see below$).$

$//$ If the substring is empty, it matches at any index.

$//$ If a start index is given, only consider matches occuring

$//$ at or to the right of that index.

size$\_$t xps$\_$find$($const char$*$ str$,$ const char$*$ substr$)$;

size$\_$t xps$\_$find$($const char$*$ str$,$ const char$*$ substr, size$\_$t start$)$;

$//$ Release the memory used to hold an XP string.

$//$ After calling this function, the memory pointed

$//$ to by str should no longer be used.

void xps$\_$free$($char$*$ str$)$;

$//$ Create a new XP string from a C string.

$//$ The new string should contain all the characters

$//$ from the C string, but stored in the XPS format.

char$*$ xps$\_$from$\_$cstr$($const char$*$ cstr$)$;

$//$ Get a single character from an XP string.

$//$ This function should not perform bounds checking;

$//$ assume the provided index is always in bounds.

char xps$\_$getchar$($const char$*$ str$,$ size$\_$t index$)$;

$//$ Get the length of an XP string.

size$\_$t xps$\_$length$($const char$*$ str$)$;

$//$ Set a single character in an XP string.

$//$ Like xps$\_$getchar$(),$ this function should not perform

$//$ bounds checking; just assume that index is valid.

void xps$\_$setchar$($char$*$ str$,$ size$\_$t index, char c$)$;

$//$ Get a substring of an XP string as a new XP string.

$//$ The new string should contain all the characters from str starting at

$//$ index start and up to but not including the character at index stop.

$//$ If stop is not given, the new string should contain all the characters

$//$ from index start until the end of the original string.

$//$ If stop is past the end of the original string, only include characters

$//$ up to the end of the original string; if start is past the end of the

$//$ original string, or if stop is less than or equal to start,

$//$ return an empty string.

char$*$ xps$\_$slice$($const char$*$ str$,$ size$\_$t start$)$;

char$*$ xps$\_$slice$($const char$*$ str$,$ size$\_$t start, size$\_$t stop$)$;