Re: [Boost-users] [regex] stuck with expression syntax / exception

Subject: Re: [Boost-users] [regex] stuck with expression syntax / exception
From: John Maddock (jz.maddock_at_[hidden])
Date: 2015-03-14 13:02:31

On 14/03/2015 16:31, Thomas wrote:
> Hi,
>
> I am pretty much a complete novice to the boost::regex library, and 
> stuck with the following snippet:
>
> std::string String = " (of 1000 elements; 67.10%)";
> try
> {
> std::cout << boost::regex_match(String, boost::regex("^ (of \\d+ 
> elements; .+%)$")) << std::endl;
> std::cout << boost::regex_match(String, boost::regex(" (of \\d+ 
> elements;.+")) << std::endl;
> }
> catch(boost::regex_error const &)
> {
> std::cout << "caught boost::regex_error!";
> }
>
> Two questions:
> First, why does the first not match?
The "(" characters are grouping operators, use "\\(" for a literal (.

> Second, why does the second throw?

Well if you'd printed out the message contained in the exception it 
would have told ;)

Same reason as above: you have a grouping ( start but no matching ).

John.

>
> The idea of the regex is that the first number is an integer, and for 
> the percentage number the formatting is unspecified but must terminate 
> with '%'; otherwise all characters must match exactly.
>
> thanks,
> Thomas
>
>
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