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xc

CharacterSet

CharacterSet is a set of byte values, stored as a 256-bit bitmap (32 bytes). Membership is O(1). String’s set-based methods (trimmed, splitOnSet, byteIndexOfSet) take one, so “any whitespace” or “any digit” is a single value rather than a hand-written test.

#import "CharacterSet.xc"        // or the Foundation umbrella

Overview

Section titled “Overview”

The set holds byte values 0–255, one bit each, so it works over the bytes of a UTF-8 string, not its code points. This suits the lexical classes it is built for (whitespace, digits, ASCII letters); it is not a Unicode character-property set. Instances are heap objects (-falloc=heap), inherit from Object, and are built either from the predefined class methods or by adding bytes to a new set.

CharacterSet* ws = CharacterSet.whitespaceAndNewlines();
String* trimmed = line.trimmed(ws);


CharacterSet* delims = CharacterSet.withCString((u8*)",;\t");
Array* fields = line.splitOnSet(delims);

Topics

Section titled “Topics”

Creating · init · withCString · withRange

Predefined sets · whitespace · newlines · whitespaceAndNewlines · decimalDigits · hexDigits · letters · alphanumerics · identifiers

Membership · contains · isEmpty

Building · add · remove · addRange · addCString

Set operations · inverted · formUnion · formIntersection

Creating

Section titled “Creating”

init

Section titled “init”
void init(void)

Initialises an empty set. Use new CharacterSet() and then add bytes, or use one of the predefined class methods below.

withCString

Section titled “withCString”
static CharacterSet* withCString(u8* s)

A set containing the bytes in the C string s, for example CharacterSet.withCString(",;\t").

withRange

Section titled “withRange”
static CharacterSet* withRange(u8 lo, u8 hi)

A set of every byte from lo to hi inclusive.

↑ Topics

Predefined sets

Section titled “Predefined sets”

Each returns a new set for a common lexical class.

whitespace

Section titled “whitespace”
static CharacterSet* whitespace(void)

Space and tab.

newlines

Section titled “newlines”
static CharacterSet* newlines(void)

The line-break characters: LF (10), CR (13), VT (11) and FF (12).

whitespaceAndNewlines

Section titled “whitespaceAndNewlines”
static CharacterSet* whitespaceAndNewlines(void)

Space, tab, CR and LF: the usual set for trimming lines.

decimalDigits

Section titled “decimalDigits”
static CharacterSet* decimalDigits(void)

0–9.

hexDigits

Section titled “hexDigits”
static CharacterSet* hexDigits(void)

0–9, a–f, A–F.

letters

Section titled “letters”
static CharacterSet* letters(void)

ASCII A–Z and a–z.

alphanumerics

Section titled “alphanumerics”
static CharacterSet* alphanumerics(void)

ASCII letters and digits.

identifiers

Section titled “identifiers”
static CharacterSet* identifiers(void)

The bytes valid in an identifier: letters, digits and _.

↑ Topics

Membership

Section titled “Membership”

contains

Section titled “contains”
bool contains(u8 c)

true if byte c is in the set. O(1).

isEmpty

Section titled “isEmpty”
bool isEmpty(void)

true if the set contains no bytes.

↑ Topics

Building

Section titled “Building”

These methods modify the set in place.

add

Section titled “add”
void add(u8 c)

Adds byte c.

remove

Section titled “remove”
void remove(u8 c)

Removes byte c.

addRange

Section titled “addRange”
void addRange(u8 lo, u8 hi)

Adds every byte from lo to hi inclusive.

addCString

Section titled “addCString”
void addCString(u8* s)

Adds every byte in the C string s.

↑ Topics

Set operations

Section titled “Set operations”

inverted

Section titled “inverted”
CharacterSet* inverted(void)

A new set of every byte not in this one.

formUnion

Section titled “formUnion”
void formUnion(CharacterSet* other)

Adds every byte of other to this set (in place).

formIntersection

Section titled “formIntersection”
void formIntersection(CharacterSet* other)

Keeps only the bytes present in both this set and other (in place).

↑ Topics