Re: [boost] boost::regex question

From: John Maddock (john_at_[hidden])
Date: 2006-10-11 04:52:13

Aljaz wrote:
> Hello..
>
> Im working on my c++ application, and I have string (user input)
> where I would have to replace some variables/substrings in it..
> For example lets say user give input:
> string str "this is test $some_variable some more text $random(1-5)
> $random(1-9)";
>
> My program has a vector <string> of variables that program should
> look for, for this case lets say "some_variable" and "random".
> Now I want to replace $some_variable and both $random 'variables' with
> another string, and I want $some_variable to be replaced with some
> other string, and $random to be replaced with random number generated
> in range from 1-5 and 1-9, for instance $random(1-5) = "3", $random(1-9) = 
> "6".
>
> So I would get "this is test some string some more text 3 6";
>
> This would be an easy thing to do, if I wouldnt have $random variable
> which makes different string each time you call it, so I'm in concern
> what would be a right/best approach to this.. I was thinking of using
> boost::regex and search with boost::regex
> expression("[%$](some_variable|random|some_more_variables)(<([^>]+)>)?");
> until I come to the string end..

I think this depends on how many variables you want to search for, the 
"scalable" solution would probably be something like:

1) Search for the regex "\\$([-[:alnum:]_]+)"
2) Use sub-expression $1 in the matched regex to look up a *functor* in a 
map<string, functor> and then call the functor - passing the matched string 
as an argument if required - and use the return value as the replacement 
string.

How does that sound?

HTH, John.