A quantifier is used to repeat an element; three of the quantifiers have already been introduced: *, +, and ?. The quantifiers are as follows:
|
Description |
Character |
Example |
|
The preceding character repeated zero or more times |
* |
'abc'-match 'a*' 'abc'-match '.*' |
|
The preceding character repeated one or more times |
+ |
'abc'-match 'a+' 'abc'-match '.+' |
|
Optional character |
? |
'abc' -match 'ab?c' 'ac' -match 'ab?c' |
|
A fixed number of characters |
{exactly} |
'abbbc' -match 'ab{3}c' |
|
A number of characters within a range |
{min,max} |
'abc' -match 'ab{1,3}c' 'abbc' -match 'ab{1,3}c' 'abbbc' -match 'ab{1,3}c' |
|
No less than a number of characters |
{min,} |
'abbc' -match 'ab{2,}c' 'abbbbbc' -match 'ab{2,}c' |
Each *, +, and ? can be described using a curly brace notation:
- * is the same as {0,}
- + is the same as {1,}
- ? is the same as {0,1}
It is extremely uncommon to find examples where the functionality of special characters is replaced with curly braces. It is equally uncommon to find examples where the quantifier {1} is used as it adds unnecessary complexity to an expression.