std::string = char* + std::string
#include <string> int main () { std::string MyString = "Testing"; MyString = " " + MyString; } This works in Microsoft Visual C++ .net 2003 The end result being MyString contans the text " Testing" I'm wondering if this is UB. Apparently MSVC is converting the " " to a std::string, then doing the +. Otherwise it would try to add a std::string to a char* which would fail. I know I can do MyString = std::string(" ") + MyString; and all would still work. But I'm wondering if I have to (to stay within the standards...

from std::string to std::istream?
Can I convert a std::string to a std::istream object? -- -Gernot int main(int argc, char** argv) {printf ("%silto%c%cf%cgl%ssic%ccom%c", "ma", 58, 'g', 64, "ba", 46, 10);} On 2005-03-17, Gernot Frisch <Me@Privacy.net> wrote: > Can I convert a std::string to a std::istream object? The question doesn't even make sense. What are you trying to do ? Cheers, -- Donovan Rebbechi http://pegasus.rutgers.edu/~elflord/ "Gernot Frisch" <Me@Privacy.net> wrote... > Can I convert a std::string to a std::istream object? No. But you can create an std::istringstream object with it: std::string mystring("1 2 3"); std::istringstream is(mystring); int one, two, three; is >> one >> two >> three; Of course, my effort is wasted if that's not what you wanted. Next time please be more verbose trying to explain what you need instead of asking about legality of a potential solution to your task. V "Victor Bazarov" <v.Abazarov@comAcast.net> schrieb im Newsbeitrag news:nPqdnXLo7cBwMqTfRVn-pQ@comcast.com... > "Gernot Frisch" <Me@Privacy.net> wrote... >> Can I convert a std::string to a std::istream object? > > No. But you can create an std::istringstream object with it: > > std::string mystring("1 2 3"); > std::istringstream is(mystring); > int one, two, three; > is >> one >> two >>...

How to extract an std::string from another std::string?
Suppose I have an std::string called line that has the value "sdsder>abc<gd<< sds". I want to get the substring between the greater- than less-than signs and assign it to another std::string called substr. How do I do this? My guess is that you should use two string iterators, one called it_begin that points to the first occurrence of a greater-than sign and another string iterator called it_end that starts at the same spot as it_begin and goes to the first occurrence of a less-than sign. Then you somehow extract the data between those two iterators. Here's what I have so far: #include <iostream> #include <string> int main() { std::string line = "sdsder>abc<gd<< sds"; std::string::iterator it_begin; std::string::iterator it_end; return 0; } Here's where I'm stumped. What value should I be assigning these two iterators? Obviously their indexes need to be six and ten, but we need to assume that line could be any string at all, not the garbage one given. How do I tell std::string to "find the first occurrence of character such-and-such and point it there"? This is a MIME GnuPG-signed message. If you see this text, it means that your E-mail or Usenet software does not support MIME signed messages. The Internet standard for MIME PGP messages, RFC 2015, was published in 1996. To open this message correctly you will need to install E-mail or Usenet software th...

std::string and std::wostream
Hi, I was wondering why there was no predefine operator<< puting a std::string into a std::wostream. The strangest is that something similar to this would work: std::wostream& operator<<(std::wostream& stream, std::string str) { stream << str.c_str(); return stream; } The only problem with this solution is it invalidate the different iterators you have on the string (because of the call to c_str), while the operator<< should not do that. Thanks, Pierre Pierre Barbier de Reuille wrote: > Hi, > > I was wondering why there was no predefine oper...

Q: Convert std::string to std::wstring using std::ctype widen()
Hi All, I've done a little homework (I've read responses to similar from P.J. Plauger and Dietmar Kuehl), and wanted to verify with the Group. Below is what I am performing (Stroustrup's Appendix D recommendation won't compile in Microsoft VC++ 6.0). My question is in reference to MultiByte Character Sets. Will this code perform as expected? I understand every problem has a simple and elegant solution that is wrong. I generally use US English or Unicode, so I don't encounter a lot of issues others may see (a multibyte character using std::string). I have verified it work...

Extracting an std::string from within another std::string
Suppose I have an std::string called data that I know has at least one greater-than sign and one less-than sign following it. I want to extract data's value to just the letters inside the greater-than and less-than signs. For example, if data = "a c>123<DDR" I want to change data to just "123". How do I do this? I'm trying to assign an std::iterator called it_begin that is set to the first occurrence of a greater-than sign, and another iterator called it_end that is set to the first occurrence of a less-than sign, then call data = data.substr(it_begin,...

std::string::push_back vs. std::string::operator+=
Hi, I just browsed libstdc++6-doc and stumbled over a string operation I haven't noticed before: string::push_back. If for example I want to append single characters to an std::string, which one would be better, or is there any difference at all: mystr.push_back( c ); or mystr += c; Any ideas? I used to use the latter one. Regards, Matthias Matthias K�ppler wrote in news:cntj5d$ooa$03$1@news.t-online.com in comp.lang.c++: > Hi, > > I just browsed libstdc++6-doc and stumbled over a string operation I > haven't noticed before: string::push_back. push_back() is there so that std::string conforms as "Back Insertion Sequence". Because its there you can use std::back_inserter with std::string for example. Or any other generic algorithm that requires a back insertion sequence. > If for example I want to append single characters to an std::string, > which one would be better, or is there any difference at all: > > mystr.push_back( c ); > > or > > mystr += c; > > Any ideas? I used to use the latter one. > Whichever you want, they both do the same thing. Rob. -- http://www.victim-prime.dsl.pipex.com/ > I just browsed libstdc++6-doc and stumbled over a string operation I haven't > noticed before: string::push_back. > If for example I want to append single characters to an std::string, which > one would be better, or is there any difference at all: > > mystr.push_back( c ); > ...

Solaris Studio C++ std::cout std::string core dump under multithread environment.
Hi, Recently I meet a very strange core dump issue and I investigate this issue for long time and I have some ideas, however I have no idea it is correct or not. So I want some guys could give me some suggestions or tips, thanks a lot. The environment: Solaris X86 64bit, Solaris Studio C++ 12 (Sun Studio C++) with -mt -pthread and libCstd.so, and use libumem library. The core dump point is as follows: // ci is a int, cn and sv is a string // and I am sure ci, cn and sv is only function local variables and they // aren't shared by multithreads cout<<" ...

std::any and std::exception_ptr
N3804 proposes the introduction of std::any. Now, C++ already has an "any"-like type, namely std::exception_ptr. Semantically, after the introduction of std::any, exception_ptr will be a special case of std::any, namely a semantical std::any initialized by a caught exception. Wouldn't it make sense to make these two interoperate nicely? In particular, ** std::exception_ptr should be able to be converted into a std::any, as, currently, the only way of looking into an exception_ptr is re-throwing and catching immediately (please correct me if I am wrong). ** std::rethro...

std::string::npos always < std::string::size() ?
Is std::string::npos always going to be less than any std::string 's size()? I am trying to handle a replacement of all occurances of a substr, in which the replacement also contains the substr. Yick. All I could come up with is: #include <string> int main() { std::string text; text = "\nThis is a test line with newlines\n<-here and \n<-here and \n\n<-two here"; // Format the text std::string formattedText(text); // Change every occurrance of "\n" to "\r\n" std::string::size_type index = 0; do { index = form...

std::any and std::exception_ptr
{ edited by mod to shorten lines to ~70 characters. -mod } [mistakenly posted to comp.lang.c++ before] N3804 proposes the introduction of std::any. Now, C++ already has an "any"-like type, namely std::exception_ptr. Semantically, after the introduction of std::any, exception_ptr will be a special case of std::any, namely a semantical std::any initialized by a caught exception. Wouldn't it make sense to make these two interoperate nicely? In particular, ** std::exception_ptr should be able to be converted into a std::any, as, currently, the only way of look...

std::string and std::ostringstream performances
Hi, I have a C++ application that extensively uses std::string and std::ostringstream in somewhat similar manner as below std::string msgHeader; msgHeader = "<"; msgHeader += a; msgHeader += "><"; msgHeader += b; msgHeader += "><"; msgHeader += c; msgHeader += ">"; Similarly it uses ostringstream as well and the function that uses this gets called almost on every message that my application gets on the socket. I am using this to precisely construct a XML Message to be sent to another application. What we observed when we ran a c...

Question about std:string and std:cout
I am a beginner of C++; I have a question about the std:string and std:cout class; Two pieces of code: -------------------------------- #include <iostream> #include <string> using namespace std; int main() { string s1 = "Hii"; string s2 = "MSDN Fans!\n"; cout<<s1+s2; } --------------------------------- #include <iostream> #include <string> using namespace std; int main() { string s1 = "Hii"; string s2 = "MSDN Fans!\n"; string s3 = s1 + s2; cout<< s3; } Which one would be run faster or they'r totally the same....

converting std::string to std::wstring
I have a an app that I'm writing which uses char and std::string. I'm using a library which expects wchar_t arrays. Is there a standard way to convert between std::string and std::wstring, or do I need to use something like std::transform()? Thanks "red floyd" <no.spam@here.dude> wrote in message news:I3ejb.539$0g6.117@newssvr29.news.prodigy.com... > I have a an app that I'm writing which uses char and std::string. I'm using > a library which expects wchar_t arrays. > > Is there a standard way to convert between std::string and std::wstring, o...

How to convert std::string to std::istream?
I have a function that use std::istream as parameter. Right now I need to pass a std::string into it, how can I convert std::string to std::istream type? Thanks Water Lin -- Water Lin's notes and pencils: http://en.waterlin.org Email: WaterLin@ymail.com Water Lin wrote: > I have a function that use std::istream as parameter. Right now I need > to pass a std::string into it, how can I convert std::string to > std::istream type? You can't directly, but you can use a stringstream: #include <iostream> #include <sstream> void f( std::istream& in ) { std::string s; in >> s; std::cout << s << std::endl; } int main() { std::string s("hello"); std::istringstream ss( s ); f( ss ); } -- Ian Collins Ian Collins <ian-news@hotmail.com> writes: > Water Lin wrote: >> I have a function that use std::istream as parameter. Right now I need >> to pass a std::string into it, how can I convert std::string to >> std::istream type? > > You can't directly, but you can use a stringstream: > > #include <iostream> > #include <sstream> > > void f( std::istream& in ) > { > std::string s; > in >> s; > std::cout << s << std::endl; > } > > int main() > { > std::string s("hello"); > std::istringstream ss( s ); > > f( ss ); > } Thanks, I got it. Water Lin -- Water Lin&...

std::map<int,std::set<std::string> > Wrong? (Segmentation fault.)
Hello, I have the following code: std::map<int,std::set<std::string> > k; k[0]="1234567890"; k[1]="2345678901"; //... std::set<std::string> myMethod(std::map<int,std::set<std::string> > k) throw(std::runtime_error) { std::map<int,std::set<std::string> >::const_iterator i; i=k.find(0); if(i==k.end()) throw std::runtime_error("No zero in k."); return i->second; } Compilation of this code goes well, but I have the following problem while executing this in my implementation: "Segmentation fault". I have pi...

which headers to #include
Suppose I have a program which uses 'ostream' type as the parameter type for a function and 'cout' object for writing into the standard output. Following is my understanding regarding, which headers to #include for this scenario. Since the program uses 'cout' object, I have to #include <iostream> header for 'cout'. In the ISO/IEC-14882:2003 document, in page 608, in section 27.3 - Standard iostream objects, the synopsis for the header <iostream> mentions the following line(apart from other statements): extern ostream cout; From the ab...

using std::string; string("hello") vs std::string("hello") in header file.
In Accellerated C++, the author recommends that in a header file one should not declare using std::string, using std::vector etc instead one should directly specify the namespace specifier in code. for example, this is bad practice: header.h #include <string> using std::string; class a{ string x; }; instead, one should write: #include <string> class a{ std::string x; }; The reason given by the author is that 'using std::string' actually pollutes the scope where 'using std::string' is declared. I find this style is rather inconvenient when I want to experiment with different implementation of certain classes in large projects. For example, I may want to try myns::string or john::string, it's actually much easier to replace 'using std::string' to 'using myns::string' and instantly switch to another string implementation. This is much better than going through all the instances of 'std::string variable' and replace them to 'myns::string variable'. What are your thoughts on this coding style? Fei Liu wrote: > In Accellerated C++, the author recommends that in a header file one > should > not declare > using std::string, using std::vector etc instead one should directly > specify > the namespace specifier in code. Doesn't it say "at top level"? > The reason given by the author is that 'using std::string' actually > pollutes > the scope where 'using...

std::bitset construction with std::string question
Can anyone tell me why std::bitset<2> foo(std::string("01")) initializes the bitset in reverse order, i.e. foo[0]=true foo[1]=false I would expect the bitset to be initialized in string text order. "Dill Hole" <dillhole@microsoft.com> wrote in message news:7brbgvs98ibjn2fcdtl7drc7tk82fstpoj@4ax.com... > Can anyone tell me why > > std::bitset<2> foo(std::string("01")) > > initializes the bitset in reverse order, i.e. > > foo[0]=true > foo[1]=false > > I would expect the bitset to be initialized in string text or...

std::fstream::seekp( ... std::ios::end )
Hi there, I think I misunderstood the purpose of std::fstream::seekp. I would like to append data at the end of a file. So I wrote the following piece of code (*). It prints '0' in my console, which means the call to seekp(0, std::ios::end) did not seek to the end of the file. How am I supposed to do that in a portable way ? (no such thing as std::ios::app) Thanks, #include <fstream> #include <iostream> int main() { const unsigned int len = 512; char buffer1[len] = {}; char buffer2[len] = {}; { std::ofstream of( "dummy.raw", std::ios::binary ); ...

Question about std:string & std:cout
I am a beginner of C++; I have a question about the std:string and std:cout class; Two pieces of code: -------------------------------- #include <iostream> #include <string> using namespace std; int main() { string s1 = "Hii"; string s2 = "MSDN Fans!\n"; cout<<s1+s2; } --------------------------------- #include <iostream> #include <string> using namespace std; int main() { string s1 = "Hii"; string s2 = "MSDN Fans!\n"; string s3 = s1 + s2; cout<< s3; } Which one would be run faster or they'r totally the same....

binary write of std::string and std::vector
Hi, I need to make binary write/read of std::string and std::vector to a file (by using ofstream/ifstream). Is there any quick way of doing this, or one has to write/read the contents element by element by using ofstream::write(buffer,size)? L.B. !!! PLEASE NOTE MY NEW ADDRESS SINCE January 1st, 2008, INDICATED BELOW !!! *-------------------------------------------------------------------* | Dr. Leslaw Bieniasz, | | Institute of Physical Chemistry of the Polish Academy of Sciences,| | Department of Complex Systems and Chemical ...

std::stringstream && std::string
Hello! I am using std::stringstream && std::string to parse a text file -> std::ifstream in; std::string s; std::streamstring ss; int n; I grab each line like so -> std::getline(in,s); I then do this to get the string into a stringstream -> ss << s; I am using a std::stringstream because it makes extracting data easier like so -> ss >> n; Is this the proper way to use std::stringstream? How do I blank out the std::stringstream object because each time I do a (ss << s;) the stream keeps concatenating onto itself...how do I blank out the stream to ad...

std::vector<char> instead of std::string, where are the string searching functions?
I am working with some legacy code that is in the process of changing to use std::vector<char> instead of a C-style char array. The C-style char array is currently allocated using new char [n]. This array is passed to various C string functions such as strstr, strncmp etc. I need to do the same work but with a std::vector. I googled around for a bit to see if I could find anyone who had already done this work but my search revealed nothing. I wonder if some kind person could point me in the right direction. Now, I realise I could code it all myself but surely there must be something out there where this has already been done. I would rather build on the work of others than re-invent the wheel. And for performance critical apps such as the one I am working on, it is common advice to use std::vector<char> instead of std::string or C- style char arrays. In the past I often seen this advice given out (it's even in More Effective STL) but without the utility functions to back it up I can see people ignoring this advice. FWIW, the app is reading in sections of a *huge* XML file. A buffer is used to hold a fragment which is then parsed using the Xerces SAX parser (thus it avoids creating a DOM object). I want the buffer to be a std::vector<char> that sometimes expands to reach a new watermark. I think I've got that bit working but the string compares fail coz it goes off the end of the vector. Regards, Andrew Marlow -- ...