Regular Expression Extension(regex)

This extension provides basic RegEx execution capabilities to Siddhi. Following are the functions of the RegEx extension.

Syntax	`<bool> regex:find (<string> regex , <string> inputSequence )`
Extension Type	Function
Description	This method attempts to find the next sub-sequence of the `inputSequence` that matches the `regex` pattern. It returns `true` if such a sub sequence exists, or returns `false` otherwise.
Examples	`find("\d\d(.)WSO2", "21 products are produced by WSO2 currently")` returns `true`. `find("\d\d(.)WSO2", "21 products are produced currently")` returns `false`.

Syntax	`<bool> regex:find (<string> regex , <string> inputSequence, <int> startingIndex )`
Extension Type	Function
Description	This method attempts to find the next sub-sequence of the `inputSequence` that matches the `regex` pattern starting from given index (i.e. `startingIndex`). It returns `true` if such a sub sequence exists, or returns `false` otherwise.
Examples	`find("\d\d(.)WSO2", "21 products are produced within 10 years by WSO2 currently by WSO2 employees", 30)` returns `true`. `find("\d\d(.)WSO2", "21 products are produced within 10 years by WSO2 currently by WSO2 employees", 35)` returns `false`.

Syntax	`<string> regex:group (<string> regex , <string> inputSequence , <int> groupId )`
Extension Type	Function
Description	Returns the input sub-sequence captured by the given group during the previous match operation. Returns `null` if no sub-sequence was found during the previous match operation. For more information about the match operation, see matches.
Example	`group("(\d\d)(.)(WSO2.)", "21 products are produced within 10 years by WSO2 currently by WSO2 employees", 3)` returns `"WSO2 employees"`.

Syntax	`<string> regex:lookingAt (<string> regex , <string> inputSequence )`
Extension Type	Function
Description	This method attempts to match the `inputSequence` against the `regex` pattern starting at the beginning.
Examples	`lookingAt("\d\d(.)WSO2", "21 products are produced by WSO2 currently in Sri Lanka"`) returns `true`. `lookingAt("WSO2(.)middleware(.*)", "sample test string and WSO2 is situated in trace and its a middleware company")` returns `false`.

Syntax	`<string> regex:matches (<string> regex , <string> inputSequence )`
Extension Type	Function
Description	This method attempts to match the entire `inputSequence` against the `regex` pattern.
Examples	`matches("WSO2(.)middleware(.)", "WSO2 is situated in trace and its a middleware company")` returns `true`. `matches("WSO2(.*)middleware", "WSO2 is situated in trace and its a middleware company")` returns `false`.