C++Talk.NET C++ language newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  help parsing strings Goto page 1, 2  Next          C++Talk.NET Forum Index -> C++ Language (Moderated) View previous topic :: View next topic   Author Message electrixnow Guest Posted: Tue Feb 07, 2006 1:00 pm    Post subject: help parsing strings in MS VC++ Express I need to know how to get from one comma delimited text string to many strings. from this: main_string = "onE,Two,Three , fouR,five, six " to these: string1 = "one" string2 = "two" string3 = "three" string4 = "four" string5 = "five" string6 = "six" the white space needs to be removed and the case needs to be all upper or lower. The result needs to be strings and not pointers or addresses in memory so I can test: I have it working but I have pointers for strings and can't convert them back to strings. string test = "three"; if (three == "three") some getlines will only have two strings some may have up to 10 Please help with examples, you input with exact syntax is greatly appreciated I have been struggling with not using pointers but every time I end up using them. Thanks in advance [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top Allan W Guest Posted: Wed Feb 08, 2006 11:00 am    Post subject: Re: help parsing strings electrixnow wrote: Quote: in MS VC++ Express I need to know how to get from one comma delimited text string to many strings. #include <cctype> #include <iostream> #include <ostream> #include <string> #include <vector> typedef std::vector<std::string> stringvec; void parse(std::string in, stringvec &out) { // Erase all entries from the vector out.swap(stringvec()); int begin=0, end=-1; while (end < int(in.length())) { // Find the next token begin = end+1; while (' '==in[begin]) ++begin; // Skip leading whitespace end = in.find(',',begin+1); if (-1==end) end=in.length(); // Skip trailing whitespace int realend=end; while (realend>begin && in[realend-1]==' ') --realend; // Convert the string to lowercase std::string x = in.substr(begin, realend-begin); int xlen = x.length(); for (int i=0; i<xlen; ++i) x[i] = std::tolower(x[i]); // Add the string to the vector out.push_back(x); } } int main() { stringvec x; parse("onE,Two,Three , fouR,five, six ",x); int size = x.size(); for (int i=0; i<size; ++i) std::cout << i << ": \"" << x[i] << "\"\n"; std::cout << "Fin" << std::endl; } [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top Carl Barron Guest Posted: Wed Feb 08, 2006 11:00 am    Post subject: Re: help parsing strings In article <1139291709.676285.84150 (AT) o13g2000cwo (DOT) googlegroups.com>, electrixnow <info...@charter.net> wrote: Quote: in MS VC++ Express I need to know how to get from one comma delimited text string to many strings. from this: main_string = "onE,Two,Three , fouR,five, six " to these: string1 = "one" string2 = "two" string3 = "three" string4 = "four" string5 = "five" string6 = "six" the white space needs to be removed and the case needs to be all upper or lower. The result needs to be strings and not pointers or addresses in memory so I can test: I have it working but I have pointers for strings and can't convert them back to strings. string test = "three"; if (three == "three") some getlines will only have two strings some may have up to 10 Please help with examples, you input with exact syntax is greatly appreciated I have been struggling with not using pointers but every time I end up using them. what do you want from "one , , two three"? A) string1 = "one"; string2 = ""; string3 = "two"; string4 = "three" or B) string1 ="one"; string2 ="two"; string3 ="three": or C) something else now if A then we are just tokenizing with whitespace or ',' and is handled in by various methods such as a token iterator provided by boost. if B then you need to tokenize with a comma and then tokenize the result with whitespace as the delimiter. again a token iterator provided by boost is one solution. if C need more details... the above are not the only solutions but the easiest to state. [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top Sumit Rajan Guest Posted: Wed Feb 08, 2006 2:00 pm    Post subject: Re: help parsing strings "electrixnow" <info...@charter.net> wrote in message news:1139291709.676285.84150 (AT) o13g2000cwo (DOT) googlegroups.com... Quote: in MS VC++ Express I need to know how to get from one comma delimited text string to many strings. You could possibly have a look at the answers to your post on clc++: http://groups.google.com/group/comp.lang.c++/browse_frm/thread/0504d4d6cd7232ff/d0592b853ca7817b?lnk=raot#d0592b853ca7817b Regards, Sumit. -- Sumit Rajan <sumitr (AT) msdc (DOT) hcltech.com> [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top Allan W Guest Posted: Wed Feb 08, 2006 8:10 pm    Post subject: Re: help parsing strings Quote: electrixnow <info...@charter.net> wrote: in MS VC++ Express I need to know how to get from one comma delimited text string to many strings. Carl Barron wrote: Quote: what do you want from "one , , two three"? A) string1 = "one"; string2 = ""; string3 = "two"; string4 = "three" or B) string1 ="one"; string2 ="two"; string3 ="three": or C) something else I think his first statement answers this question... "comma delimited". So the answer is A. [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top Seungbeom Kim Guest Posted: Mon Feb 13, 2006 7:06 am    Post subject: Re: help parsing strings Allan W wrote: Quote: typedef std::vector<std::string> stringvec; void parse(std::string in, stringvec &out) { // Erase all entries from the vector out.swap(stringvec()); I'm just curious: why out.swap(stringvec()) instead of out.clear()? Is it better in any way? -- Seungbeom Kim [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top Joe Guest Posted: Mon Feb 13, 2006 3:06 pm    Post subject: Re: help parsing strings Seungbeom Kim wrote: Quote: I'm just curious: why out.swap(stringvec()) instead of out.clear()? Is it better in any way? out.clear() doesn't free any memory allocated to the vector itself. In other words, if you had 100 strings in the vector, a clear would destroy all those strings and reset the size to 0, but there would still be space reserved for those 100 string objects. The swap() idiom not only causes the vector to free the objects stored in it, but it also frees up any memory reserved for the vector itself. This is also a handy idiom for various implementations of a hash_map or hash_set where you may get a significant chunk of memory reserved to the collection that won't get returned to the OS via clear(). As with any idiom, the value depends upon how big a problem the unreclaimed memory might be versus the unobviousness of the idiom. Once folks get used to seeing it, the latter factor becomes less and less. joe [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top Seungbeom Kim Guest Posted: Tue Feb 14, 2006 1:06 am    Post subject: Re: help parsing strings Joe wrote: Quote: Seungbeom Kim wrote: I'm just curious: why out.swap(stringvec()) instead of out.clear()? Is it better in any way? out.clear() doesn't free any memory allocated to the vector itself. In other words, if you had 100 strings in the vector, a clear would destroy all those strings and reset the size to 0, but there would still be space reserved for those 100 string objects. The swap() idiom not only causes the vector to free the objects stored in it, but it also frees up any memory reserved for the vector itself. I see, thanks. Now I remember seeing this idiom before. :) Quote: As with any idiom, the value depends upon how big a problem the unreclaimed memory might be versus the unobviousness of the idiom. Once folks get used to seeing it, the latter factor becomes less and less. I don't think the unreclaimed memory would be a big problem, especially if more items would be added soon later as in the Allan's example. Often when you have to start by clearing a vector given as an argument, you can make the interface clearer by using a locally defined vector and returning it later: // #1 void parse(std::string in, stringvec &out) { // Erase all entries from the vector out.swap(stringvec()); // Fill out } // #2 stringvec parse(std::string in) { stringvec out; // Fill out return out; } -- Seungbeom Kim [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top Allan W Guest Posted: Tue Feb 14, 2006 5:06 pm    Post subject: Re: help parsing strings Seungbeom Kim wrote: Quote: Often when you have to start by clearing a vector given as an argument, you can make the interface clearer by using a locally defined vector and returning it later: // #1 void parse(std::string in, stringvec &out) { // Erase all entries from the vector out.swap(stringvec()); // Fill out } // #2 stringvec parse(std::string in) { stringvec out; // Fill out return out; } This returns the entire vector by value. NVRO could cause the copy to be skipped... but compilers that don't implement this optimization could copy the entire vector and every element in the vector. Yes, yes, premature optimization and all that... but optimization is much easier if you can avoid changing the function signature. In #2 the vector is a return value. If profiling showed that it was important to change to #1 for performance reasons, then depending on how often the function was called, this change could be quite painful. [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top Eugene Kalenkovich Guest Posted: Wed Feb 15, 2006 2:06 pm    Post subject: Re: help parsing strings "Allan W" <allan_w@my-dejanews.com> wrote in message news:1139334963.068333.15180 (AT) g43g2000cwa (DOT) googlegroups.com... Quote: // Erase all entries from the vector out.swap(stringvec()); Does it work? For what compiler/version? The last one that allowed this construct that I am aware of was VC 6.0 -- EK [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top Allan W Guest Posted: Thu Feb 16, 2006 2:06 am    Post subject: Re: help parsing strings Quote: "Allan W" <allan_w@my-dejanews.com> wrote // Erase all entries from the vector out.swap(stringvec()); Eugene Kalenkovich wrote: Quote: Does it work? For what compiler/version? The last one that allowed this construct that I am aware of was VC 6.0 As far as I know, this is a standard idiom. I tested it on .Net 2003, and it sure seems to work, as verified by out.capacity(). What compiler/version does this NOT work on? [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top kanze Guest Posted: Sat Feb 18, 2006 1:06 am    Post subject: Re: help parsing strings Allan W wrote: Quote: "Allan W" <allan_w@my-dejanews.com> wrote // Erase all entries from the vector out.swap(stringvec()); Eugene Kalenkovich wrote: Does it work? For what compiler/version? The last one that allowed this construct that I am aware of was VC 6.0 As far as I know, this is a standard idiom. I tested it on .Net 2003, and it sure seems to work, as verified by out.capacity(). What compiler/version does this NOT work on? It shouldn't compile on a standard conforming compiler; it requires binding a temporary to a non-const reference. The *standard* idiom is to use swap, either the reverse: stringvec().swap( out ) ; or to use an explicit temporary: stringvec empty ; out.swap( empty ) ; -- James Kanze GABI Software Conseils en informatique orientée objet/ Beratung in objektorientierter Datenverarbeitung 9 place Sémard, 78210 St.-Cyr-l'École, France, +33 (0)1 30 23 00 34 [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top Eugene Kalenkovich Guest Posted: Sat Feb 18, 2006 1:06 am    Post subject: Re: help parsing strings "Allan W" <allan_w@my-dejanews.com> wrote in message news:1140034430.302925.253230 (AT) o13g2000cwo (DOT) googlegroups.com... Quote: "Allan W" <allan_w@my-dejanews.com> wrote // Erase all entries from the vector out.swap(stringvec()); Eugene Kalenkovich wrote: Does it work? For what compiler/version? The last one that allowed this construct that I am aware of was VC 6.0 As far as I know, this is a standard idiom. I tested it on .Net 2003, and it sure seems to work, as verified by out.capacity(). What compiler/version does this NOT work on? On any standard-compliant compiler. Even MS, AFAIR since 2003 version, gives a warning (on level 4) that this conversion is not standard-compliant. Swap (STL swaps, you can define your own differently, though other signatures make no sense) accepts non-const reference; it means that only lvalue can be accepted. -- EK [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top electrixnow Guest Posted: Sat Feb 18, 2006 5:06 am    Post subject: Re: help parsing strings You replied on parsing strings. I have a problem with code that follows. it only returns 4 for the sizeof &tokens. Why? #include <cstring> #include <iostream> #include <string> #include <vector> using namespace std; void Tokenize(const string& str, vector<string>& tokens, const string& delimiters = " ,\t\n") { // Skip delimiters at beginning. string::size_type lastPos = str.find_first_not_of(delimiters, 0); // Find first "non-delimiter". string::size_type pos = str.find_first_of(delimiters, lastPos); while (string::npos != pos || string::npos != lastPos) { // Found a token, add it to the vector. tokens.push_back(str.substr(lastPos, pos - lastPos)); // Skip delimiters. Note the "not_of" lastPos = str.find_first_not_of(delimiters, pos); // Find next "non-delimiter" pos = str.find_first_of(delimiters, lastPos); } } int main() { vector<string> tokens; string str(";1,2,3,4,5,6,7,8,9,0"); // replace with getline string start = str.substr(0,1); if(start == ";")cout<<"HELLO WORLD"<<'\n'; // skip this line for comments int len = str.length(); for (int a=0; a<len; ++a) str[a]=toupper(str[a]); Tokenize(str, tokens); for (int i=0;i<sizeof(&tokens);++i){ // check amount of tokens cout << tokens[i]<<'\n'; } } Thanks, Grant [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top Carl Barron Guest Posted: Sat Feb 18, 2006 5:06 am    Post subject: Re: help parsing strings In article <1140034430.302925.253230 (AT) o13g2000cwo (DOT) googlegroups.com>, Allan W <allan_w@my-dejanews.com> wrote: Quote: "Allan W" <allan_w@my-dejanews.com> wrote // Erase all entries from the vector out.swap(stringvec()); Eugene Kalenkovich wrote: Does it work? For what compiler/version? The last one that allowed this construct that I am aware of was VC 6.0 As far as I know, this is a standard idiom. I tested it on .Net 2003, and it sure seems to work, as verified by out.capacity(). What compiler/version does this NOT work on? Should NOT work on any compliant compiler, swap wants a non-constant referenece and conversion of a temporary [stringvec()] to a non constant reference is the no-no. but { stringvec t; out.swap(t); } is just fine. [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. 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