User:OrenBochman/Lua Strings Advanced
Pattern Matching with Regular Expressions
[edit]Lua supports string matching using regualr expressions. Regular expressions are defined with the following symbols:
- ( - start group
- ) - end group
- . - any single character
- % - escape character
- + - 1 or more greedy
- * - 0 or more greedy
- - - 0 or more not greedy
- ? - 0 or one
- [ - start range
- ] - end range
- ^ - string start
- $ - string end
Character Classes
[edit]There are some predefined ranges:
- . - all characters
- %a - letters
- %l - lower case
- %u - upper case
- %d - digits
- %h - hexadecimal digits
- %w - alphanumeric characters
- %p - punctuation characters
- %s - whitespace
- %c - control characters
upper case version of these is the complement range.
s = "Deadline is 30/05/1999, firm"
date = "%d%d/%d%d/%d%d%d%d"
print(string.sub(s, string.find(s, date))) --> 30/05/1999
print(string.gsub("hello, up-down!", "%A", ".")) --> hello..up.down. 4
here 4 is the count of substitutions returned by gsub
to count the number of Vowel in a string
dummy, nvow = string.gsub(text, "[AEIOUaeiou]", "")
where the dummy variable holds the vowel free string and nvow has the result.