c++ - How to create a compile time constant instance of a structure in C++11 -

-

in current project trying create compile time const static instance of structure c++11. code compiles , works fine in clang (apple llvm version 6.1.0) not work g++ (gcc) 4.8.3. gcc throws error parameter not declared 'constexpr'. there way make work in gcc? 

//parameter.h struct par {     const int uniqid;     const char *name;     const char *description;     constexpr par(int uid,const char * n,const char * d)              :uniqid(uid), name(n),description(d){} };  class parameters           {     const static par param_a;     ...     const static par param_z;     printparameters(std::vector<par> parameters); };  //parameter.cpp constexpr par parameters::param_a={0,"-a","bla a"}; ...  constexpr par parameters::param_z={0,"-z","bla z"};  void parameters::printparameters(std::vector<par> parameters){      (size_t = 0; < parameters.size(); i++) {         switch (parameters[i].uniqid) {            case param_a.uniqid:                  std::cout << "a" << std::endl;                 break;         } }

the gcc following: 

parameters.cpp:11:39: error: declaration of ‘const par parameters::param_a’ outside of class not definition [-fpermissive] parameters.cpp:12:39: error: redeclaration ‘parameters::param_a’ differs in ‘constexpr’  constexpr par parameters::param_a={...};  in file included parameters.cpp:2:0:         parameters.h:190:34: note: ‘parameters::param_a’ not declared 'constexpr' const static par param_a;

i think problem declare param_a , param_z const in parameter.h , define them constexpr in parameter.cpp. const , constexpr different things. in parameter.cpp must have this:

//parameter.cpp const par parameters::param_a={0,"-a","bla a"}; ...  const par parameters::param_z={0,"-z","bla z"};

Comments

Post a Comment

Popular posts from this blog

java - Custom OutputStreamAppender not run: LOGBACK: No context given for <MYAPPENDER> -

-
i wish write custom appender on basis of outputstreamappender . wrote following class package tests; import java.io.ioexception; import java.io.outputstream; import ch.qos.logback.core.outputstreamappender; public class myappender<e> extends outputstreamappender<e> { public myappender() { system.out.println("myappender created"); setoutputstream(new outputstream() { @override public void write(int b) throws ioexception { throw new unsupportedoperationexception(); } }); } } then wrote following runner: package tests; import org.slf4j.loggerfactory; import ch.qos.logback.classic.logger; public class runner { private static final logger log = (logger) loggerfactory.getlogger(runner.class); public static void main(string[] args) { //log.addappender(new myappender<iloggingevent>()); log.info("hello world"); } } finall...
Read more

java - UML - How would you draw a try catch in a sequence diagram? -

-
Image
is there standard way of drawing try catch sequence diagrams? i've made attempt based on this feel end result doesn't feel right. code diagram based around: public static void save () { try { filehandle filehandle = gdx.files.external(file); filehandle.writestring(boolean.tostring(constantshandler.soundenabled)+"\n", false); (int = 0; < 5; i++) { filehandle.writestring(integer.tostring(constantshandler.highscores[i])+"\n", true); } } catch (throwable e) { } } my attempt note: know still need add loop. that's ok. fragments meant show conditional control flow in sequence diagram. superstructures puts limitations on use of fragments (see pp. 467 of ss2.1.1). should use critical region try part above. , option catch . however, keep telling can take quite freedom in using uml. it's language , such changes in life time. long reader ge...
Read more

c++ - No viable overloaded operator for references a map -

-
i trying use map can make tag names reference number. when try , use it, in code error (6 in total every time reference map): src/main.cpp:25:45: error: no viable overloaded operator[] type 'std::map<std::string, std::string>' const char* idcs = node.child_value(tagmap[3]); this code: #include "pugi/pugixml.hpp" #include <iostream> #include <string> #include <map> int main() { pugi::xml_document doca, docb; std::map<std::string, pugi::xml_node> mapa, mapb; std::map<std::string, std::string> tagmap {{"1", "data"}, {"2", "entry"}, {"3", "id"}, {"4", "content"}}; if (!doca.load_file("a.xml") || !docb.load_file("b.xml")) { std::cout << "can't find input files"; return 1; } (auto& node: doca.child(tagmap[1]).children(tagmap[2])) { co...
Read more