Re: [Boost-users] [string_algo] Split and Predicates

28 Jan 2005

      Hi,

On Thu, Jan 27, 2005 at 03:38:04PM -0800, David Brownell wrote:
...
I am attempting to split a string with the string_algo library, using the
code below.  It appears that the split algorithm is designed to split on
instances of individual characters rather than sequences of characters.  Is
there something I can do to split on a substring?  The code below
illustrates the problem, where I am forces to use the is_any_of predicate
rather than something that implies equality.  It seems like this is a
trivial use of the algorithm, so there could easily be something that I am
missing.
typedef std::vector >
ResultsType;
ResultsType             results;
    static char const       STRING[] = "this\r\nis\r\n\r\na test!";
boost::split(results, 
                 boost::iterator_range(STRING, STRING +
sizeof(STRING)), 
                 boost::is_any_of("\r\n"));  // The problem is here.  I
would like to be able 
                                             // to use something like
equals, but split requires 
                                             // a predicate that takes a
single argument rather than 
                                             // a range.
for(ResultsType::const_iterator rptr = results.begin(); 
        rptr != results.end(); 
        ++rptr)
            std::cout << "'" << std::string(rptr->begin(), rptr->end()) <<
"'\n";
It is possible to achieve what you want quite easily. However, split algorithm
is not the right tool for this.
Split is a high level wrapper over the split_iterator and it is quite specialized.

So this is the code, that should work for you:

   #include 
   #include 

   static char const       STRING[] = "this\r\nis\r\n\r\na test!";

   typedef boost::split_iterator char_split_iterator;

   for(char_split_iterator It=char_split_iterator(STRING, boost::first_finder("\r\n");
       It!=char_split_iterator();
       ++It)
    {
        cout << *It << endl;
    }

This example will split the STRING in the tokens, delimited by "\r\n".
Note, that instead of first_finder, you can use any other one. Even the custom one.
Check the documentation for more details.
There is also an example in boost/libs/algorithm/string/example/split_example.cpp

Regards,

Pavol

PS: I have not tried to compile the example, so please be patient it there are some errors.

Re: [Boost-users] [string_algo] Split and Predicates

Pavol Droba