validate s If s is valid UCS4 then successes otherwise raises Malformed_code. Other functions assume strings are valid UCS4, so it is prudent to test their validity for strings from untrusted origins.

get s n returns n-th Unicode character of s.

init len f returns a new string which contains len Unicode characters. The i-th Unicode character is initialised by f i

length s returns the number of Unicode characters contained in s

Positions in the string represented by the number of characters from the head. The location of the first character is 0

nth s n returns the position of the n-th Unicode character. The call requires O(n)-time

first s : The position of the head of the last Unicode character.

last s : The position of the head of the last Unicode character.

look s i returns the Unicode character of the location i in the string s.

out_of_range s i tests whether i points the valid position of s.

compare_aux s i1 i2 returns If i1 is the position located before i2, a value < 0, If i1 and i2 points the same location, 0, If i1 is the position located after i2, a value > 0.

next s i returns the position of the head of the Unicode character located immediately after i. If i is a valid position, the function always success. If i is a valid position and there is no Unicode character after i, the position outside s is returned. If i is not a valid position, the behaviour is undefined.

prev s i returns the position of the head of the Unicode character located immediately before i. If i is a valid position, the function always success. If i is a valid position and there is no Unicode character before i, the position outside s is returned. If i is not a valid position, the behaviour is undefined.

move s i n : If n >= 0, returns n-th Unicode character after i. If n < 0, returns -n-th Unicode character before i. If there is no such character, the result is unspecified.

iter f s : Apply f to all Unicode characters in s. The order of application is same to the order in the Unicode characters in s.

Code point comparison

Buffer module for UCS4