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Regex pattern to match Switch Case statements.

Answer 1

+3 A:

Since switch statements can be nested traditional regexes can't handle them (heck, even the fact that the {} can be nested breaks them). Regexes can only parse Regular Languages. You need some form of parser to parse languages that are not regular. Depending on what language you have (it looks like C, but so do a lot of things), there may already be a parser you can use (such as Sparse for C).

Chas. Owens 2009-05-26 14:42:21

Hi, We don't have nested switches.

SharePoint Newbie 2009-05-26 14:51:19

Answer 2

+1 A:

Here is something to start with but it is far from perfect - the expression does not recognize defaults and the end of the switch statement (and maybe includes some other errors).

(?sn:(case (?<label>[^:]+):[ \r\n\t]*)+(?<body>((?!case).)*))

UPDATE

It will also fail if the body contains case as part of a string or an identifier.

Daniel Brückner 2009-05-26 15:07:48

Answer 3

A:

Chas. Owens is correct in his comment. But for simple cases, you can maybe use the following regex:

switch\s*\((?<expression>[^\)]+)\)\s*\{\s*((default(?<case>)|case\s*(?<case>"[^"]*"|'[^']*'|\w+))\s*:\s*(?<body>((?!\s*(case\b|default\b|\}))("[^"]*"|'[^']*'|[^\}]))*)\s*)+\}

To use it, the regex engine you're using should support explicit multiple named captures and look-aheads (such as the .NET regex engine). Note that all groups except for the named groups can be made non-capturing, but in order to make the regex easier to understand I didn't add the "?:" at the group start to make them non-capturing groups.

You'll then get one match for each recognized switch statement with the following captures:

expression: the expression used for the switch (1 capture)
case: the case label, or empty (but a successful capture) for the default
body: the case body, one for each case

case and body will always come as pairs, so that you can enumerate through the captures.

Lucero 2009-05-26 15:36:48

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Regex pattern to match Switch Case statements.

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