RegExp sub1 = RegExp(r'boo(hoo)*'); // Matches zero or more occurrences of 'hoo', i.e would match 'boo', 'boohoo', 'boohoohoo',...
sub1.hasMatch('boo'); // true
sub1.hasMatch('boohoo'); // true
sub1.hasMatch('boohoohoo'); // true
sub1.hasMatch('hoo'); // false


RegExp sub2 = RegExp(r'What would you( like to)? say'); // ' like to' is optional. This would match 'What would you like to say' and also 'What would you say'
sub2.hasMatch('What would you like to say'); // true
sub2.hasMatch('What would you say') // true
sub2.hasMatch('What you say'); // false

RegExp sub3 = RegExp(r'(Meow ?){3,5}'); // This would match between 3 and 5 occurrences of 'Meow '
sub3.hasMatch('Meow'); // false
sub3.hasMatch('Meow Meow Meow'); // true
sub3.hasMatch('Meow Meow Meow Meow'); // true

RegExp fruit = RegExp(r'orange|banana|pineapple|water melon|apple'); // This would match one of 'orange', 'banana', 'pineapple', 'water melon' and 'apple'
                    
RegExp regExp1 = RegExp(r'1 girl|(2|3|4) girls'); // This would match one of '1 girl', '2 girls', '3 girls', '4 girls'

RegExp word1 = RegExp(r'\bstand\b'); // matches a string that has a separate word 'stand'
word1.hasMatch('I understand'); // false
word1.hasMatch('You have understanding'); // false
word1.hasMatch('I am standing'); // false
word1.hasMatch('I stand'); // true

RegExp word2 = RegExp(r'\bstand'); // matches a string that contains 'stand' at the beginning of a word

word2.hasMatch('I understand'); // false
word2.hasMatch('You have understanding'); // false
word2.hasMatch('I am standing'); // true
word2.hasMatch('I stand'); // true

RegExp word3 = RegExp(r'stand\b'); // matches a string that contains 'stand' at the end of a word

word3.hasMatch('I understand'); // true
word3.hasMatch('You have understanding'); // false
word3.hasMatch('I am standing'); // false
word3.hasMatch('I stand'); // true

RegExp string1 = RegExp(r'^stand$'); // Matches a string that contains only 'stand'
string1.hasMatch('stand now'); // false
string1.hasMatch('now stand'); // false
string1.hasMatch('stand'); //true

RegExp string2 = RegExp(r'^stand'); // Matches a string that starts with 'stand'
string2.hasMatch('stand now'); // true
string2.hasMatch('now stand'); // false
string2.hasMatch('stand'); // true

RegExp string3 = RegExp(r'stand$'); // Matches a string that ends with 'stand'
string3.hasMatch('stand now'); // false
string3.hasMatch('now stand'); // true
string3.hasMatch('stand'); // true

// Here there are two named group subexpressions; 'number' and 'animal' ('s' is optional)
RegExp named = RegExp(r'(?<number>\d+) (?<animal>cat|dog|cow|pig)s?'); 
                    
// RegExpMatch: regular expression matches, may be null(if no match)
RegExpMatch? match1 = named.firstMatch('5 dogs');
match1?.namedGroup('number'); // '5'
match1?.namedGroup('animal'); // 'dog'

RegExpMatch? match2 = named.firstMatch('10 cats');
match2?.namedGroup('number'); // '10'
match2?.namedGroup('animal'); // 'cat'

RegExpMatch? match3 = named.firstMatch('1 pig');
match3?.namedGroup('number'); // '1'
match3?.namedGroup('animal'); // 'pig'

RegExp nonMulti = RegExp(r'end$'); // multiline: false
RegExp multi = RegExp(r'end$', multiLine: true);
String testString = 'This is the end\nThis is another line';

nonMulti.hasMatch(testString); // false
multi.hasMatch(testString); // true

RegExp sensitive = RegExp(r'This is a pattern'); // caseSensitive: true
RegExp insensitive = RegExp(r'This is a pattern', caseSensitive: false);

sensitive.hasMatch('This Is A Pattern'); // false
insensitive.hasMatch('This Is A Pattern'); // true

RegExp nonUnicode = RegExp(r'\u{0221}'); // unicode: true
RegExp unicode = RegExp(r'\u{0221}', caseSensitive: false);

nonUnicode.hasMatch('ȡ'); // false
unicode.hasMatch('ȡ'); // true

RegExp nonDotAll = RegExp(r'^.+$'); // dotAll: false
RegExp dotAll = RegExp(r'^.+$', dotAll: true);
String testString = 'This is the end\nThis is another line';

nonDotAll.hasMatch(testString); // false
dotAll.hasMatch(testString); // true

// This would match a string like a string like '$500.26'
// '\$' escapes the special meaning of end of string and matches '$'
// '\d+' means 1 or more digit characters
// '\.' escapes the special meaning of '.'(matching any string except newline) and matches only '.'
// '\d{2}' means exactly 2 digit characters
RegExp money = RegExp(r'\$\d+\.\d{2}');
money.hasMatch('\$10578.43'); // true ('$' is also a special character in dart)

String testString = 'Superman45';
                    
final greedy = RegExp(r'^(?\w+)(?\d*)$'); // Greedy matching on the 'letters' group subexpression
final greedyMatch = greedy.firstMatch('Superman45');

greedyMatch?.namedGroup('letters'); // 'Superman45' // Matches whole string
greedyMatch?.namedGroup('digits'); // '' // The digits are not extracted

final nonGreedy = RegExp(r'^(?\w+?)(?\d*)$'); // Non-greedy matching on the 'letters' group subexpression

final nonGreedyMatch = nonGreedy.firstMatch('Superman45');

nonGreedyMatch?.namedGroup('letters') // 'Superman'
nonGreedyMatch?.namedGroup('digits'); // '45'

RegExp regExp = RegExp(r'love');
regExp.hasMatch('I love you.'); // true
regExp.hasMatch('I hate you.'); // false

RegExp regExp = RegExp(r'(?(?\d+) (?cat|dog|cow|pig)s?)');
String records = '5 cats, 4 dogs, 9 cows and 15 pigs';

RegExpMatch? firstMatch = regExp.firstMatch(records); // Finds only first match
print(firstMatch?.namedGroup('record')); // '5 cats'
print(firstMatch?.namedGroup('number')); // '5'
print(firstMatch?.namedGroup('animal')); // 'cat'
print(firstMatch?[0]); // '5 cats' (whole match)
print(firstMatch?[1]): // '5 cats' (first subexpression)
print(firstMatch?[2]): // '5' (second subexpression)
print(firstMatch?[3]): // 'cat' (third subexpression)

Iterable allMatches = regExp.allMatches(records); // Finds all matches
for (RegExpMatch match in allMatches) {
  print(match.namedGroup('record')) // '5 cats', '4 dogs', '9 cows', '15 pigs'
  print(match.namedGroup('number')) // '5', '4', '9', '15'
  print(match.namedGroup('animal')) // 'cat', 'dog', 'cow', 'pig'
}

Iterable allMatchesWithStartIndex = regExp.allMatches(records, 8); // Finds all matches from index 8
for (RegExpMatch match in allMatchesWithStartIndex) {
  print(match.namedGroup('record')) // 4 dogs', '9 cows', '15 pigs'
  print(match.namedGroup('number')) // '4', '9', '15'
  print(match.namedGroup('animal')) // 'dog', 'cow', 'pig'
}

RegExp regExp = RegExp(r'\d(\d(\d)(\d))(\d(\d(\d)(\d)))\d');
RegExpMatch? match = regExp.firstMatch('012345678');

print(match?[0]); // '012345678'
print(match?[1]); // '123'
print(match?[2]); // '2'
print(match?[3]); // '3'
print(match?[4]); // '4567'
print(match?[5]); // '567'
print(match?[6]); // '6'
print(match?[7]); // '7'

String originString = 'This is the origin string';
RegExp pattern = RegExp(r'origin'); // Matches the word 'origin'
String replace = 'first';
                        
print(originString.replaceFirst(pattern, replace)); // 'This is the first string'

String originString = 'Almost all information will be lost';
RegExp pattern = RegExp(r'\b\w+\b'); // Matches all words
String replace = 'lost';

print(originString.replaceAll(pattern, replace)); // 'lost lost lost lost lost lost'

RegExp regExp = RegExp(r'(\w+)\s(\w+)'); 
String lastFirst = 'Smith John';
String firstLast = lastFirst.replaceFirstMapped(regExp,
(Match m) => '${m[2]} ${m[1]}'
);
print(firstLast); // 'John Smith'

RegExp regExp = RegExp(r'(\w+)\s(\w+)'); // Matches a name
String lastFirst = 'Smith John\nNakamura Hikaru\nAdebayo Peter\nMa Long';
String firstLast = lastFirst.replaceAllMapped(regExp,
(Match m) => '${m[2]} ${m[1]}'
);
print(firstLast); // 'John Smith\nHikaru Nakamura\nPeter Adebayo\nLong Ma'