[C++] valeur par défaut

void f(double & a,double& b,double c=2.3){
  b = 1.2;   // --- Default start value
} 

void traite (char** a,double& b,double& c,const double &l=1.2,char* u)
{
...}

traite.h:15: assignement of read-only reference 'l'

void f(const double & x,const double & y=2.3,const double & z=7.6){
  ...
}

(mando@cobo) (~) $ cat plop.cpp
#include <iostream>

void f(const float & x,const float & y=6.9,const float & z=2.8){
        std::cout << x << ' ' << y << ' ' << z << ' ' << std::endl;
}

int main(){
        f(1.2);
        return 0;
}
(mando@cobo) (~) $ g++ -W -Wall plop.cpp
(mando@cobo) (~) $ ./a.out
1.2 6.9 2.8

#include <iostream>

int f(const double & x,const double & y = 0,const char * z = NULL){
    std::cout << x << ' ' << y << ' ' << z << std::endl;
    std::cout << std::endl;
}

void traite (char** a,const double & b,const double & c,const double &l=1.2,char* u=NULL){
    std::cout << "*a=" << *a << std::endl;
    std::cout << "b=" << b << std::endl;
    std::cout << "c=" << c << std::endl;
    std::cout << "l=" << l << std::endl;
    std::cout << "u=" << u << std::endl;
    std::cout << std::endl;
}

int main(){
    f(1,2.5,"tapir");
    char * plop = "plop";
    traite(&plop,2.3,4.2,4.8,"mando");
    return 0;
}