Re: [Boost-users] Tokenizer: BCB AnsiString and std:string

CN wrote:

Hi!

The following version incorrectly produces the result:

< > 1

//---------------------- #include<iostream> #include #include #pragma hdrstop #pragma argsused int main(int argc, char* argv[]) { using namespace std; using namespace boost; AnsiString As = "*"; typedef tokenizer Tok; char_separator<char> sep(", "); Tok tokens(string(As.c_str(),As.Length()), sep); for(Tok::iterator tok_iter = tokens.begin();tok_iter != tokens.end(); ++tok_iter) cout << "<" << *tok_iter << "> " << (*tok_iter).size(); return EXIT_SUCCESS; } //----------------------

However, this version correctly outputs this result:

<*> 1

#include<iostream> #include #include #pragma hdrstop #pragma argsused int main(int argc, char* argv[]) { using namespace std; using namespace boost; AnsiString As = "*"; string str=string(As.c_str(),As.Length()); typedef tokenizer Tok; char_separator<char> sep(", "); Tok tokens(str, sep); for(Tok::iterator tok_iter = tokens.begin();tok_iter != tokens.end(); ++tok_iter) cout << "<" << *tok_iter << "> " << (*tok_iter).size(); return EXIT_SUCCESS; } //----------------------

Why the firt version mulfunctions?

TIA and Regards,

CN

The first version creates a temporary string that only exists for long enough to call tokens' constructor, and a tokenizer keeps pointers into the string it was built on, not a list of the tokens (for space reasons), so immediately after tokens is constructed, it has a list of pointers to a dead variable (this is a Bad Thing, and you are lucky this didn't work the first time, rather than silently stop working later). The second version has a real variable holding the string, and therefore the pointers are still alive. Why don't you just use 'As' directly? Does AnsiString not provide begin()/end()? If it's just that it's versions are differently named you can do: Tok tokens(As.Begin(), As.End(), sep);// Or whatever begin()/end() are PS: It's conventional to name variables with a lower-case first letter.