試験CPP トピック3 問題209 スレッド

What happens when you attempt to compile and run the following code?
# include <deque>
# include <iostream>
# include <algorithm>
using namespace std;
class B { int val;
public:
B(int v):val(v){}
int getV() const {return val;} bool operator < (const B & v) const { return val<v.val;} }; ostream & operator <<(ostream & out, const B & v) { out<<v.getV(); return out;} template<class T>struct Out {
ostream & out; Out(ostream & o): out(o){}
void operator() (const T & val ) { out<<val<<" "; } };
int main() {
int t[]={20, 30, 10, 20, 30, 10, 20, 30, 10, 20};
deque<B> d1(t, t+10);
sort(d1.begin(), d1.end());
pair<deque<B> ::iterator, deque<B>::iterator > result = equal_range(d1.begin(), d1.end(),
B(20));
for_each(result.first, result.second, Out<B>(cout));cout<<endl;
return 0;
}
Program outputs: