CODEWITHSUNDEEP
c++visual-c++boostboost-regex
user1553605
user1553605

Reputation: 1393

how to define a regular expression in boost?

I have a section in file:

[Source]

[Source.Ia32]


[Source.Ia64]

I have created the expression as:

const boost::regex source_line_pattern ("(Sources)(.*?)");

Now, I am trying to match the string, but I am not able to match; it is always returning 0.

if (boost::regex_match ( sToken, source_line_pattern ) )
  return TRUE;

Please note that sToken value is [Source]. [Source.Ia32]... and so on.

Thanks,

Upvotes: 0

Views: 179

Answers (2)

James Kanze
James Kanze

Reputation: 153929

There are at least two problems with your code. First, the regular expression you give contains the literal string "Sources", and not "Source", which is what you seem to be trying to match. The second is that boost::regex_match is bound: it must match the entire string. What you seem to want is boost::regex_search. Depending on what you are doing, however, it might be better to try to match the entire string: "\\[Source(?:\\.(\\w+))?\\]\\s*". Which provides for capture of the trailing part, if present (but not the leading "Source"---no point, in general, in capturing something that is a constant).

Note too that the sequence ".*?" is very dubious. Normally, I would expect the regular expression parser to fail if a (non-escaped) '*' is followed by a '?'.

Upvotes: 2

Dave S
Dave S

Reputation: 21113

The issue is that boost::regex_match only returns true if the entire input string is matched by the regex. So the '[' and ']' are not matched by your current regex, and it will fail.

Your options are either to use boost::regex_search, which will search for a substring of the input that matches your regex, or modify your regex to accept the entire string being passed in.

Upvotes: 1

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