March 2007 - Boost-users - lists.preview.boost.org

lambda usage
by Peng Yu 15 Mar '07

15 Mar '07

Hi, It seems that the lambda manual lacks of a simple working example. I'm made up the following example. But it's not working. Could you please show me how to make it work? Thanks, Peng #include <boost/lambda/lambda.hpp> #include <boost/lambda/core.hpp> #include <iostream> using namespace boost::lambda; int main() { std::cout << (_1 + _2)(10, 10) << std::endl; }

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[lamba] Comparing return value of member function with ->*
by Boris 15 Mar '07

15 Mar '07

struct sample { int i; sample(int i) : i(i) { } bool odd() { return i % 2; } }; template <class T, class U> std::basic_ostream<T, U> &operator<<(std::basic_ostream<T, U>& ostr, sample s) { return ostr << s.i; } std::vector<sample> from; std::vector<sample> to; from.push_back(sample(1)); from.push_back(sample(2)); from.push_back(sample(3)); // Why doesn't this compile ... std::for_each(from.begin(), from.end(), if_then((_1 ->* &sample::odd) == false, std::cout << _1)); // ... but this does? Isn't it the same? std::for_each(from.begin(), from.end(), if_then(bind(&sample::odd, _1) == false, std::cout << _1)); Thanks in advance for any explanation which helps me to understand lamba expressions better, Boris

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libraries accepted to boost
by andrzej 15 Mar '07

15 Mar '07

Hello, In the Boost home page I can see a number of libraries were accepted to Boost even more than a year ago. When are they going to be included in the official release? Thanks, &rzej ---------------------------------------------------------------------- Seksowne dziewczyny, szybkie samochody Zobacz >> http://link.interia.pl/f1a28

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How to convert this into lambda expression
by Peng Yu 14 Mar '07

14 Mar '07

Hi, I have the following code which requires a definition of a class "not_fun". I want to replace it with lambda expression. Would you please let me know what the best way would be? Thanks, Peng #include <iostream> template <bool B> class not_fun; template <> struct not_fun<true> { static bool doit(bool x) { return x; } }; template <> struct not_fun<false> { static bool doit(bool x) { return !x; } }; template <bool B> class A { public: A() { } bool compute(bool b) const { if(not_fun<B>::doit(b)) // how replace this with lambda expression? return true; return false; } private: }; int main() { A<true> a; std::cout << a.compute(true) << std::endl; }

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C++ - STL & Shared memory
by Borse, Ganesh 14 Mar '07

14 Mar '07

Hi, I am developing an application with 2 unrelated, arbitary processes having a C++ shared hash map between them to store data. However, I am facing the problem of creating this template hash map in shared memory. Can boost be used for this purpose? Can anybody please suggest me the implementation which can be used to do this? Thanks in advance. Best Regards, Ganesh B. ============================================================================== Please access the attached hyperlink for an important electronic communications disclaimer: http://www.credit-suisse.com/legal/en/disclaimer_email_ib.html ==============================================================================

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SQL library with full embedded SQL-syntax
by Dmitriy Lyfar 14 Mar '07

14 Mar '07

Hi I would like to participate in Google Summer of Code in this year. I reviewed boost projects for last years and found an interesting project, I think. If you go to the link below you will see a short description for that library: http://www.crystalclearsoftware.com/cgi-bin/boost_wiki/wiki.pl?Google_Summe… The goal of this post is to define the main library features, which will be useful for users. Is that library useful for C++ community? If you are using(or have ever used) similar C++ libraries for work with SQL: which of features do you want to have? Also I want to notice one of the biggest beauty of that approach: you can get the compiler to type-check the SQL-expression, what do you think about that? Thank you. Best regards, Lyfar Dmitriy

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how can I explicitly specify the lambda namespace
by Dmitriy Chumack 14 Mar '07

14 Mar '07

hi * In the documentation for lambda library from boost_1_33_1, in section "Getting Started"->"Conventions used in this document" said that in all examples implicitly used such declarations: using namespace std; using namespace boost::lambda; So the following will work: for_each(a.begin(), a.end(), std::cout << _1 << ' '); But how do I have to rewrite the above line of code to have it compiled without "using namespace boost::lambda;" before it? Thanks in advance.

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Re: [Boost-users] Any function in boost::regex to escape everything of a text
by llwaeva＠21cn.com 14 Mar '07

14 Mar '07

> hi there, > I am working with a pattern-replace job with boost:regex. For > convenience, I use replace_all_regex to do that. Here is my code > > replace_all_regex( TEXT_TO_BE_REPLACED, regex_exp, format_string, > format_all ); > > TEXT_TO_BE_REPLACED is a text containing some patterns like %a, %b > and %c which will be repalced with a specific string(format_string) > that is inputed by user. However, the input string (format_string) > may have some characters related to the regular expression, such > characters must be escaped before the substitution. The following > > code is for that purpose > > > > replace_all( input, "$", "$$" ); > > replace_all( input, "\\", "\\\\" ); > > replace_all( input, ":", "\\:" ); > > replace_all( input, "?", "\\?" ); >> > replace_all( input, "(", "\$" ); > > replace_all( input, ")", "\$" ); > > > > The substitution works fine sometimes and fails when the input string > > (format_string) contains character which is not escaped. I just > > wonder if there is any function defined in boost::regex to escape all > > SPECIAL characters. > Use "format_literal" rather than "format_all" and all the characters in the > format string will be output "as is", and none will be treated as special > characters. > John. I try format_literal, but it reports error while compiling "error C2065: 'format_literal' : undeclared identifier" I am using the latest version of boost. Microsoft Visual Studio 2005, XP

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[program_options] Unsure about linking options
by Ovanes Markarian 13 Mar '07

13 Mar '07

Hi! I am not sure if this is the issue of the program_options library or of all libraries at all. I got the HEAD revision from CVS and successfully compiled required libraries. One of the required libs is program_options. I have variations of the compiled lib with a name as: boost_program_options-vc-mt-1_35.lib When I try to recompile my code I get a linking error stating: LINK : fatal error LNK1104: cannot open file 'libboost_program_options-vc80-mt-gd-1_35.lib' My question is: Why is compiler still looking for libboost_program_options-vc80-mt-gd-1_35.lib? Do I have to change some config files? If yes, which? With Kind Regards, Ovanes Markarian

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iostream and mapped_file
by Aljaz 13 Mar '07

13 Mar '07

Hello Is there any example how to use boost::iostream mapped_file ? I couldnt find any.. Which are the reasons that should make me consider using mapped_file stream? I want to read my text file as fast as possible (not all at once) - it should be seekable.. I know I should open file in binary mode and do read() to fixed size blocks to achieve the best preformance, but then I would have problems separating lines (I was consider using tokenizer but it would require stl data type so I would have to copy data). Is it possible to solve this problem with using boost::iostream filter so that it would be faster than getline()? Any help is highly appreciated! Thank you very much Aljaz

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