里面一句代码看不懂.
//: C06:NString.h// From "Thinking in C++, Volume 2", by Bruce Eckel & Chuck Allison.
// (c) 1995-2004 MindView, Inc. All Rights Reserved.
// See source code use permissions stated in the file 'License.txt',
// distributed with the code package available at www.
// A "numbered string" that keeps track of the
// number of occurrences of the word it contains.
#ifndef NSTRING_H
#define NSTRING_H
#include <algorithm>
#include <iostream>
#include <string>
#include <utility>
#include <vector>
typedef std::pair<std::string, int> psi;
// Only compare on the first element
bool operator==(const psi& l, const psi& r) {
return l.first == r.first;
}
class NString {
std::string s;
int thisOccurrence;
// Keep track of the number of occurrences:
typedef std::vector<psi> vp;
typedef vp::iterator vpit;
static vp words;
void addString(const std::string& x) {
psi p(x, 0);
vpit it = std::find(words.begin(), words.end(), p);
if(it != words.end())
thisOccurrence = ++it->second;
else {
thisOccurrence = 0;
words.push_back(p);
}
}
public:
NString() : thisOccurrence(0) {}
NString(const std::string& x) : s(x) { addString(x); }
NString(const char* x) : s(x) { addString(x); }
// Implicit operator= and copy-constructor are OK here.
friend std::ostream& operator<<(
std::ostream& os, const NString& ns) {
return os << ns.s << " [" << ns.thisOccurrence << "]";
}
// Need this for sorting. Notice it only
// compares strings, not occurrences:
friend bool
operator<(const NString& l, const NString& r) {
return l.s < r.s;
}
friend
bool operator==(const NString& l, const NString& r) {
return l.s == r.s;
}
// For sorting with greater<NString>:
friend bool
operator>(const NString& l, const NString& r) {
return l.s > r.s;
}
// To get at the string directly:
operator const std::string&() const { return s; }//请问这句是什么意思?
};
NString::vp NString::words; ///////请问这句代码是什么意思啊?
#endif // NSTRING_H ///:~
[ 本帖最后由 q1826050194 于 2012-7-14 14:34 编辑 ]
