Mikroelektronika MIKROE-742 데이터 시트

Any item of a regular expression may be followed by another type of metacharac-
ters - iterators. Using this metacharacters,you can specify number of occurences of
previous character, metacharacter or subexpression. 

- zero or more ("greedy"), similar to {0,} 

- one or more ("greedy"), similar to {1,} 

- zero or one ("greedy"), similar to {0,1} 

- exactly n times ("greedy") 

- at least n times ("greedy") 

- at least n but not more than m times ("greedy") 

- zero or more ("non-greedy"), similar to {0,}? 

- one or more ("non-greedy"), similar to {1,}? 

- zero or one ("non-greedy"), similar to {0,1}? 

- exactly n times ("non-greedy") 

- at least n times ("non-greedy") 

- at least n but not more than m times ("non-greedy") 

So, digits in curly brackets of the form, 

{n,m}

, specify the minimum number of times to

match the item 

and the maximum 

. The form 

is equivalent to 

and matches

exactly 

times. The form 

matches 

or more times. There is no limit to the size of

or 

, but large numbers will chew up more memory and slow down execution.

If a curly bracket occurs in any other context, it is treated as a regular character.

- matches strings like 

'

'countelkjdflkj9r' 

and 

'

countr'

- matches strings like 

'

'countelkjdflkj9r'

but not 

'

countr'

- matches strings like 

'

counter', 'countar'

and 

'

countr'

but not

'

countelkj9r' 

- matches string 

'

counteer'

- matches strings like

'

counteer'

, 

'

counteeer'

, 

'

counteeer'

etc. 

- matches strings like 

'

counteer'

, or 

'

counteeer'

but not 

'

teeeer' 

A little explanation about "greediness". "Greedy" takes as many as possible, "non-
greedy" takes as few as possible. 
For example, 

'

b+'

and 

'

b*'

applied to string 

'

abbbbc'

return 

'

bbbb', 'b+?'

returns 

'

b', 'b*?'

returns empty string, 

'

b{2,3}?'

returns 

'

bb'

, 

'

b{2,3}'

returns 

'

bbb'

. 

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- SOFTWARE AND HARDWARE SOLUTIONS FOR EMBEDDED WORLD

CHAPTER 2