Datasheet

Metacharacters - Iterators

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}

{n} - exactly n times ("greedy")

{n,} - at least n times ("greedy")

{n,m} - 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}?

{n}? - exactly n times ("non-greedy")

{n,}? - at least n times ("non-greedy")

{n,m}? - 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 n and the maximum m. The form {n} is equivalent to {n,n} and match-

es exactly

n times. The form {n,} matches n or more times. There is no limit to the size

of n or m, 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.

Examples:

count.*r ß- matches strings like 'counter', 'countelkjdflkj9r' and 'countr'

count.+r

- matches strings like 'counter', 'countelkjdflkj9r' but not 'countr'

count.?r

- matches strings like 'counter', 'countar' and 'countr' but not

'countelkj9r'

counte{2}r

- matches string 'counteer'

counte{2,}r

- matches strings like 'counteer', 'counteeer', 'counteeer' etc.

counte{2,3}r - matches strings like 'counteer', or 'counteeer' but not 'coun-

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'.

MIKROELEKTRONIKA - SOFTWARE AND HARDWARE SOLUTIONS FOR EMBEDDED WORLD

Environment

mikroBasic PRO for AVR

CHAPTER 2