Q
qazmlp
The following code is taken from:
http://www.sgi.com/tech/stl/Map.html
As the keytype is 'const char*' in the std::map object, there is a
special comparator function used here. But, when I run this program,
I never get "Inside comparator" printed. What exactly is happening?
I am just wondering how the insertion( via std::map:perator[]()) and
std::map::find() works properly without the comparator function
getting used.
Kindly clarify!
--------------------------------------
struct ltstr
{
bool operator()(const char* s1, const char* s2) const
{
std::cout << "Inside comparator\n" ;
return strcmp(s1, s2) < 0;
}
};
int main()
{
map<const char*, int, ltstr> months;
months["january"] = 31;
months["february"] = 28;
months["march"] = 31;
months["april"] = 30;
months["may"] = 31;
months["june"] = 30;
months["july"] = 31;
months["august"] = 31;
months["september"] = 30;
months["october"] = 31;
months["november"] = 30;
months["december"] = 31;
cout << "june -> " << months["june"] << endl;
map<const char*, int, ltstr>::iterator cur = months.find("june");
map<const char*, int, ltstr>::iterator prev = cur;
map<const char*, int, ltstr>::iterator next = cur;
++next;
--prev;
cout << "Previous (in alphabetical order) is " << (*prev).first <<
endl;
cout << "Next (in alphabetical order) is " << (*next).first << endl;
}
--------------------------------------------------------------
http://www.sgi.com/tech/stl/Map.html
As the keytype is 'const char*' in the std::map object, there is a
special comparator function used here. But, when I run this program,
I never get "Inside comparator" printed. What exactly is happening?
I am just wondering how the insertion( via std::map:perator[]()) and
std::map::find() works properly without the comparator function
getting used.
Kindly clarify!
--------------------------------------
struct ltstr
{
bool operator()(const char* s1, const char* s2) const
{
std::cout << "Inside comparator\n" ;
return strcmp(s1, s2) < 0;
}
};
int main()
{
map<const char*, int, ltstr> months;
months["january"] = 31;
months["february"] = 28;
months["march"] = 31;
months["april"] = 30;
months["may"] = 31;
months["june"] = 30;
months["july"] = 31;
months["august"] = 31;
months["september"] = 30;
months["october"] = 31;
months["november"] = 30;
months["december"] = 31;
cout << "june -> " << months["june"] << endl;
map<const char*, int, ltstr>::iterator cur = months.find("june");
map<const char*, int, ltstr>::iterator prev = cur;
map<const char*, int, ltstr>::iterator next = cur;
++next;
--prev;
cout << "Previous (in alphabetical order) is " << (*prev).first <<
endl;
cout << "Next (in alphabetical order) is " << (*next).first << endl;
}
--------------------------------------------------------------