标签：c++primer
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12.1 动态内存与智能指针
1.在C++中，动态内存的管理是通过一对运算符来完成：new，在动态内存中为对象分配空间并返回一个指向该对象的指针，我们可以选择对对象进行初始化；delete，接受一个动态对象的指针，销毁该对象，并释放与之关联的内存。
2.
shared_ptr允许多个指针指向同一个对象；unique_ptr则“独占”所指向的对象。标准库还定义了一个名为weak_ptr的伴随类，它是一种弱引用，指向shared_ptr所管理的对象。这三种类型都定义在memory头文件中。
3.
shared_ptr和unique_ptr都支持的操作
shared_ptr<T> sp
unique_ptr<T> up 空智能指针，可以指向类型为T的对象
p 将p用作一个条件判断，若p指向一个对象，则为true
*p 解引用p，获得它指向的对象
p->mem 等价于(*p).mem
p.get() 返回p中保存的指针。要小心使用，若智能指针释放了其对象，返回的指针所指向的对象也就消失了。
swap(p,q)
p.swap(q) 交换p和q中的指针
4.
shared_ptr独有的操作
make_shared<T>(args) 返回一个shared_ptr，指向一个动态分配的类型为T的对象。使用args初始化对象。
make_shared<T>p(q) p是shared_ptr q的拷贝；此操作会递增q中的计数器。q中的指针必须能转换为T*
p = q p和q都是shared_ptr，所保存的指针必须能相互转换。此操作会递减p的引用计数，递增q的引用计数；若p的引用计数变为0，则将其管理的原内存释放。
p.unique() 若p.use_count()为1，返回true；否则返回false
p.use_count() 返回与p共享对象的智能指针数量；可能很慢，主要用于测试
5.
由内置指针(而不是智能指针)管理的动态内存在被显式释放以前一直都会存在。
6.
定义和改变shared_ptr的其他方法
shared_ptr<T> p(q) p管理内置指针q所指向的对象；q必须指向new分配的内存，且能够转换为T*类型
shared_ptr<T> p(u) p从unique_ptr u那里接管了对象的所有权，将u置为空
shared_ptr<T> p(q,d) p接管了内置指针q所指向的对象的所有权。q必须能转换为T*类型。p将使用可调用对象d来代替delete
shared_ptr<T> p(p2,d) p是shared_ptr p2的拷贝，唯一的区别是p将用可调用对象d来代替delete
p.reset()
p.reset(q)
p.reset(q,d) 若p是唯一指向其对象的shared_ptr，reset会释放此对象。若传递了可选的参数内置指针q，会令p指向q，否则会将p置为空。若还传递了参数d，将会调用d而不是delete来释放q
7.
为了正确使用智能指针，我们必须坚持一些基本规范
⑴不使用相同的内置指针值初始化(或reset)多个智能指针
⑵不delete get()返回的指针
⑶不使用get()初始化或reset另一个智能指针
⑷如果你使用get()返回的指针，记住当最后一个对应的智能指针销毁后，你的指针就变成无效了
⑸如果你使用智能指针管理的资源不是new分配的内存，记住传递给它一个删除器
8.
unique_ptr操作
unique_ptr<T> u1
unique_ptr<T,p> u2 空unique_ptr，可以指向类型为T的对象。u1会使用delete来释放它的指针；u2会使用一个类型为D的可调用对象来释放它的指针
unique_ptr<T,p> u(d) 空unique_ptr，指向类型为T的对象，用类型为D的对象d代替delete
u = nullptr 释放u所指向的对象，将u置为空
u.release u放弃对指针的控制权，返回指针，并将u置为空
u.reset() 释放u指向的对象
u.reset(q)
u.reset(nullptr) 如果提供了内置指针q，令u指向这个对象；否则将u置为空
9.
weak_ptr操作
weak_ptr<T> w 空weak_ptr可以指向类型为T的对象
weak_ptr<T> w(sp) 与shared_ptr sp指向相同对象的weak_ptr。T必须能转换为sp指向的类型。
w = p p可以是一个shared_ptr或一个weak_ptr。赋值后w与p共享对象
w.reset() 将w置为空
w.use_count() 与w共享对象的shared_ptr的数量
w.expired() 若w.use_count()为0，返回true，否则返回false
w.lock() 如果expired为true，返回一个空shared_ptr；否则返回一个指向w的对象的shared_ptr
12.2 动态数组
1.动态数组并不是数组类型，而是得到一个数组元素类型的指针。
2.
指向数组的unique_ptr
指向数组的unique_ptr不支持成员访问运算符
其他unique_ptr操作不变
unique_ptr<T[]> u u可以指向一个动态分配的数组，数组元素类型为T
unique_ptr<T[]> u(p) u指向内置指针p所指向的动态分配的数组。p必须能转换为类型T*
u[i] 返回u拥有的数组中位置i处的对象，u必须指向一个数组
3.标准库allocator类定义在头文件memory中，它帮助我们将内存分配和对象构造分离开来。它提供一种类型感知的内存分配方法，它分配的内存是原始的，未构造的。
4.
标准库allocator类及其算法
allocator<T> a 定义了一个名为a的allocator对象，它可以为类型为T的对象分配内存
a.allocator(n) 分配一段原始的，未构造的内存，保存n个类型为T的对象
a.deallocate(p,n) 释放从T*指针p中地址开始的内存，这块内存保存了n个类型为T的对象；p必须是一个先前由allocate返回的指针，且n必须是p创建时所要求的大小。在调用deallocate之前，用户必须对每个在这块内存中创建的对象调用destory。
a.construct(p,args) p必须是一个类型为T*的指针，指向一块原始内存；arg被传递给类型为T的构造函数，用来在p指向的内存中构造一个对象
a.destroy(p) p为T*类型的指针，此算法对p指向的对象指向析构函数
5.
allocator算法
这些函数在给定目的位置创建元素，而不是由系统分配内存给它们。
uninitialized_copy(b,e,b2) 从迭代器b和e指出的输入范围中拷贝元素到迭代器b2指定的未构造的原始内存中。b2指向的内存必须足够大，能容纳输入序列中元素的拷贝
uninitialized_copy_n(b,n,b2)
从迭代器b指向的元素开始，拷贝n个元素到b2开始的内存中
uninitialized_fill(b,e,t)
在迭代器b和e指定的原始内存范围中创建对象，对象的值均为t的拷贝
uninitialized_fill_n(b,n,t) 从迭代器b指向的内存地址开始创建n个对象。b必须指向足够大的未构造的原始内存，能够容纳给定数量的对象
PS：部分练习答案
练习12.1
b2被销毁，但是b2里面的元素不会被销毁，所以b1，b2都有4个元素
练习12.2
ex12_02.h
#include <vector>
#include <string>
#include <initializer_list>
#include <memory>
#include <exception>
using std::vector;
using std::string;
class StrBlob
{
public:
using size_type = vector<string>::size_type;
StrBlob():data(std::make_shared<vector<string>>()) {}
StrBlob(std::initializer_list<string> il):data(std::make_shared<vector<string>>(il)) {}
size_type size() const
{
return data->size();
}
bool empty() const
{
return data->empty();
}
void push_back(const string& t)
{
data->push_back(t);
}
void pop_back()
{
check(0,"pop_back on empty StrBlob");
data->pop_back();
}
std::string& front()
{
check(0,"front on empty StrBlob");
return data->front();
}
std::string& back()
{
check(0,"back on empty StrBlob");
return data->back();
}
const std::string& front() const
{
check(0,"front on empty StrBlob");
return data->front();
}
const std::string& back() const
{
check(0,"back on empty StrBlob");
return data->back();
}
private:
void check(size_type i,const string& msg) const
{
if(i>=data->size())
throw std::out_of_range(msg);
}
private:
std::shared_ptr<vector<string>> data;
};
#include <iostream>
#include "ex12_02.h"
int main()
{
const StrBlob csb{"one","two","three"};
StrBlob sb{"one","two","four"};
std::cout << csb.front() << " " << csb.back() << std::endl;
sb.back() = "three";
std::cout << sb.front() << " " << sb.back() << std::endl;
}练习12.6
#include <iostream>
#include <vector>
#include <string>
#include <memory>
std::vector<int>* dynamic_vector_generator()
{
std::vector<int>* ptr_v = new std::vector<int>();
return ptr_v;
}
void dynamic_vector_processor(std::vector<int>* ptr_v)
{
int i;
std::cout << "please enter:" << std::endl;
while(std::cin >> i && i!=999)
ptr_v->push_back(i);
}
void dynamic_vector_printer(std::vector<int>* ptr_v)
{
for(const auto& elem: *ptr_v)
std::cout << elem << " ";
std::cout << std::endl;
}
int main()
{
std::vector<int>* ptr_vi = dynamic_vector_generator();
dynamic_vector_processor(ptr_vi);
dynamic_vector_printer(ptr_vi);
delete ptr_vi;
return 0;
}#include <iostream>
#include <vector>
#include <string>
#include <memory>
std::shared_ptr<std::vector<int>> dynamic_vector_generator_sptr()
{
return std::make_shared<std::vector<int>>();
}
void dynamic_vector_processor_sptr(std::shared_ptr<std::vector<int>> sptr_vi)
{
int i;
std::cout << "please enter:" << std::endl;
while(std::cin >> i && i!=999)
sptr_vi->push_back(i);
}
void dynamic_vector_printer_sptr(const std::shared_ptr<std::vector<int>> sptr_vi)
{
for(const auto& elem: *sptr_vi)
std::cout << elem << " ";
std::cout << std::endl;
}
int main()
{
auto sptr = dynamic_vector_generator_sptr();
dynamic_vector_processor_sptr(sptr);
dynamic_vector_printer_sptr(sptr);
return 0;
}#include <iostream>
#include <string>
#include <memory>
struct connection
{
std::string ip;
int port;
connection(std::string ip_,int port_):ip(ip_),port(port_){}
};
struct destination
{
std::string ip;
int port;
destination(std::string ip_,int port_):ip(ip_),port(port_){}
};
connection connect(destination* pDest)
{
std::shared_ptr<connection> pConn(new connection(pDest->ip,pDest->port));
std::cout << "creating connection(" << pConn.use_count() << ")" << std::endl;
return *pConn;
}
void disconnect(connection pConn)
{
std::cout << "connection close(" << pConn.ip << ":" << pConn.port << ")" << std::endl;
}
void end_connection(connection* pConn)
{
disconnect(*pConn);
}
void f(destination& d)
{
connection conn = connect(&d);
std::shared_ptr<connection> p(&conn,end_connection);
std::cout << "connection now(" << p.use_count() << ")" << std::endl;
}
int main()
{
destination dest("202.118.176.67",3316);
f(dest);
return 0;
}#include <iostream>
#include <string>
#include <memory>
struct connection
{
std::string ip;
int port;
connection(std::string ip_,int port_):ip(ip_),port(port_){}
};
struct destination
{
std::string ip;
int port;
destination(std::string ip_,int port_):ip(ip_),port(port_){}
};
connection connect(destination* pDest)
{
std::shared_ptr<connection> pConn(new connection(pDest->ip,pDest->port));
std::cout << "creating connection(" << pConn.use_count() << ")" << std::endl;
return *pConn;
}
void disconnect(connection pConn)
{
std::cout << "connection close(" << pConn.ip << ":" << pConn.port << ")" << std::endl;
}
void f(destination& d)
{
connection conn = connect(&d);
std::shared_ptr<connection> p(&conn,[](connection* pConn){disconnect(*pConn);});
std::cout << "connection now(" << p.use_count() << ")" << std::endl;
}
int main()
{
destination dest("202.118.176.67",3316);
f(dest);
return 0;
}ex12_19.h
#ifndef CP5_ex12_19_h
#define CP5_ex12_19_h
#include <vector>
#include <string>
#include <initializer_list>
#include <memory>
#include <exception>
using std::vector;
using std::string;
class StrBlobPtr;
class StrBlob
{
public:
using size_type = vector<string>::size_type;
friend class StrBlobPtr;
StrBlobPtr begin();
StrBlobPtr end();
StrBlob():data(std::make_shared<vector<string>>()) {}
StrBlob(std::initializer_list<string> il):data(std::make_shared<vector<string>>(il)){}
size_type size() const
{
return data->size();
}
bool empty() const
{
return data->empty();
}
void push_back(const string& t)
{
data->push_back(t);
}
void pop_back()
{
check(0,"pop_back on empty StrBlob");
data->pop_back();
}
std::string& back()
{
check(0, "back on empty StrBlob");
return data->back();
}
const std::string& front() const
{
check(0, "front on empty StrBlob");
return data->front();
}
const std::string& back() const
{
check(0, "back on empty StrBlob");
return data->back();
}
private:
void check(size_type i,const string& msg) const
{
if(i>=data->size())
throw std::out_of_range(msg);
}
private:
std::shared_ptr<vector<string>> data;
};
class StrBlobPtr
{
public:
StrBlobPtr():curr(0){}
StrBlobPtr(StrBlob& a,size_t sz = 0):wptr(a.data),curr(sz){}
bool operator!=(const StrBlobPtr& p)
{
return p.curr!=curr;
}
string& deref()const
{
auto p = check(curr,"dereference past end");
return (*p)[curr];
}
StrBlobPtr& incr()
{
check(curr,"increament past end of StrBlobPtr");
++curr;
return *this;
}
private:
std::shared_ptr<vector<string>> check(size_t i,const string& msg) const
{
auto ret = wptr.lock();
if(!ret)
throw std::runtime_error("unbound StrBlobPtr");
if(i>=ret->size())
throw std::out_of_range(msg);
return ret;
}
std::weak_ptr<vector<string>> wptr;
size_t curr;
};
#endif#include "ex12_19.h"
StrBlobPtr StrBlob::begin()
{
return StrBlobPtr(*this);
}
StrBlobPtr StrBlob::end()
{
return StrBlobPtr(*this,data->size());
}#include "ex12_19.h"
#include <fstream>
#include <iostream>
int main()
{
std::ifstream ifs("book.txt");
StrBlob blob;
for(std::string str; std::getline(ifs,str);)
blob.push_back(str);
for(StrBlobPtr pbeg(blob.begin()),pend(blob.end()); pbeg!=pend; pbeg.incr())
std::cout<<pbeg.deref()<<std::endl;
}ex12_22.h
#ifndef CP5_ex12_22_h
#define CP5_ex12_22_h
#include <vector>
#include <string>
#include <initializer_list>
#include <memory>
#include <exception>
using std::vector;
using std::string;
class ConstStrBlobPtr;
class StrBlob
{
public:
using size_type = vector<string>::size_type;
friend class ConstStrBlobPtr;
StrBlobPtr begin() const;
StrBlobPtr end() const;
StrBlob():data(std::make_shared<vector<string>>()) {}
StrBlob(std::initializer_list<string> il):data(std::make_shared<vector<string>>(il)) {}
size_type size() const
{
return data->size();
}
bool empty() const
{
return data->empty();
}
void push_back(const string& t)
{
data->push_back(t);
}
void pop_back()
{
check(0,"pop_back on empty StrBlob");
data->pop_back();
}
std::string& back()
{
check(0, "back on empty StrBlob");
return data->back();
}
const std::string& front() const
{
check(0, "front on empty StrBlob");
return data->front();
}
const std::string& back() const
{
check(0, "back on empty StrBlob");
return data->back();
}
private:
void check(size_type i,const string& msg) const
{
if(i>=data->size())
throw std::out_of_range(msg);
}
private:
std::shared_ptr<vector<string>> data;
};
class ConstStrBlobPtr
{
public:
ConstStrBlobPtr():curr(0) {}
ConstStrBlobPtr(const StrBlob& a,size_t sz = 0):wptr(a.data),curr(sz) {}
bool operator!=(ConstStrBlobPtr& p)
{
return p.curr!=curr;
}
const string& deref()const
{
auto p = check(curr,"dereference past end");
return (*p)[curr];
}
ConstStrBlobPtr& incr()
{
check(curr,"increament past end of StrBlobPtr");
++curr;
return *this;
}
private:
std::shared_ptr<vector<string>> check(size_t i,const string& msg) const
{
auto ret = wptr.lock();
if(!ret)
throw std::runtime_error("unbound StrBlobPtr");
if(i>=ret->size())
throw std::out_of_range(msg);
return ret;
}
std::weak_ptr<vector<string>> wptr;
size_t curr;
};
#endif#include "ex12_19.h"
ConstStrBlobPtr StrBlob::begin() const
{
return ConstStrBlobPtr(*this);
}
ConstStrBlobPtr StrBlob::end() const
{
return ConstStrBlobPtr(*this,data->size());
}#include <iostream>
#include <string>
#include <cstring>
int main()
{
char *concatenate_string = new char[255]();
strcat(concatenate_string,"hello ");
strcat(concatenate_string,"world");
std::cout << concatenate_string << std::endl;
delete[] concatenate_string;
std::string str1{"hello "},str2{"world"};
std::cout << str1+str2 << std::endl;
}#include <iostream>
int main()
{
std::cout << "How long do you want the string? ";
int size {0};
std::cin >> size;
char* input = new char[size + 1]();
std::cin.ignore();
std::cout << "input the string: ";
std::cin.get(input, size + 1);
std::cout << input;
delete[] input;
}#include <iostream>
#include <string>
#include <memory>
void input_reverse_output_string(int n)
{
std::allocator<std::string> alloc;
auto const p = alloc.allocate(n);
std::string s;
auto q = p;
while(std::cin >> s && q!=p+n) alloc.construct(q++,s);
while(q!=p)
{
std::cout << *--q << " ";
alloc.destroy(q);
}
alloc.deallocate(p,n);
}
int main()
{
input_reverse_output_string(5);
return 0;
}ex12_27_30.h
#ifndef CP5_ex12_27_h
#define CP5_ex12_27_h
#include <string>
using std::string;
#include <vector>
using std::vector;
#include <memory>
using std::shared_ptr;
#include <iostream>
#include <fstream>
#include <map>
#include <set>
class QueryResult;
class TextQuery
{
public:
using LineNo = vector<string>::size_type;
TextQuery(std::ifstream&);
QueryResult query(const string&) const;
private:
shared_ptr<vector<string>> input;
std::map<string, shared_ptr<std::set<LineNo>>> result;
};
class QueryResult
{
public:
friend std::ostream& print(std::ostream&, const QueryResult&);
public:
QueryResult(const string& s, shared_ptr<std::set<TextQuery::LineNo>> set,
shared_ptr<vector<string>> v)
: word(s), nos(set), input(v)
{
}
private:
string word;
shared_ptr<std::set<TextQuery::LineNo>> nos;
shared_ptr<vector<string>> input;
};
std::ostream& print(std::ostream&, const QueryResult&);
#endif#include "ex12_27_30.h"
#include <sstream>
#include <algorithm>
TextQuery::TextQuery(std::ifstream& ifs) : input(new vector<string>)
{
LineNo lineNo {0};
for (string line; std::getline(ifs, line); ++lineNo)
{
input->push_back(line);
std::istringstream line_stream(line);
for (string text, word; line_stream >> text; word.clear())
{
std::remove_copy_if(text.begin(), text.end(),
std::back_inserter(word), ispunct);
auto& nos = result[word];
if (!nos) nos.reset(new std::set<LineNo>);
nos->insert(lineNo);
}
}
}
QueryResult TextQuery::query(const string& str) const
{
static shared_ptr<std::set<LineNo>> nodate(new std::set<LineNo>);
auto found = result.find(str);
if (found == result.end())
return QueryResult(str, nodate, input);
else
return QueryResult(str, found->second, input);
}
std::ostream& print(std::ostream& out, const QueryResult& qr)
{
out << qr.word << " occurs " << qr.nos->size()
<< (qr.nos->size() > 1 ? " times" : " time") << std::endl;
for (auto i : *qr.nos)
out << "\t(line " << i + 1 << ") " << qr.input->at(i) << std::endl;
return out;
}#include "ex12_27_30.h"
#include <iostream>
void runQueries(std::ifstream& infile)
{
TextQuery tq(infile);
while (true)
{
std::cout << "enter word to look for, or q to quit: ";
string s;
if (!(std::cin >> s) || s == "q") break;
print(std::cout, tq.query(s)) << std::endl;
}
}
int main()
{
std::ifstream file("<span style="color: rgb(24, 54, 145); font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; line-height: 16px; white-space: pre;">storyDataFile</span>.txt");
runQueries(file);
}#include <string>
#include <vector>
#include <memory>
#include <iostream>
#include <fstream>
#include <sstream>
#include <map>
#include <set>
#include <algorithm>
using std::string;
using std::vector;
using std::shared_ptr;
int main()
{
std::ifstream file("letter.txt");
vector<string> input;
std::map<string, std::set<decltype(input.size())>> dictionary;
decltype(input.size()) lineNo {0};
for (string line; std::getline(file, line); ++lineNo)
{
input.push_back(line);
std::istringstream line_stream(line);
for (string text, word; line_stream >> text; word.clear())
{
std::remove_copy_if(text.begin(), text.end(),
std::back_inserter(word), ispunct);
dictionary[word].insert(lineNo);
}
}
while (true)
{
std::cout << "enter word to look for, or q to quit: ";
string s;
if (!(std::cin >> s) || s == "q") break;
auto found = dictionary.find(s);
if (found != dictionary.end())
{
std::cout << s << " occurs " << found->second.size()
<< (found->second.size() > 1 ? " times" : " time")
<< std::endl;
for (auto i : found->second)
std::cout << "\t(line " << i + 1 << ") " << input.at(i)
<< std::endl;
}
else
std::cout << s << " occurs 0 time" << std::endl;
}
}ex12_32.h
#ifndef CP5_ex12_32_h
#define CP5_ex12_32_h
#include "ex12_22.h"
using std::shared_ptr;
#include <iostream>
#include <fstream>
#include <map>
#include <set>
class QueryResult;
class TextQuery
{
public:
TextQuery(std::ifstream&);
QueryResult query(const string&) const;
private:
shared_ptr<StrBlob> input;
std::map<string, shared_ptr<std::set<StrBlob::size_type>>> result;
};
class QueryResult
{
public:
friend std::ostream& print(std::ostream&, const QueryResult&);
public:
QueryResult(const string& s, shared_ptr<std::set<StrBlob::size_type>> set,
shared_ptr<StrBlob> v)
: word(s), nos(set), input(v)
{
}
private:
string word;
shared_ptr<std::set<StrBlob::size_type>> nos;
shared_ptr<StrBlob> input;
};
std::ostream& print(std::ostream&, const QueryResult&);
#endif#include "ex12_32.h"
#include <sstream>
#include <algorithm>
TextQuery::TextQuery(std::ifstream& ifs) : input(new StrBlob)
{
StrBlob::size_type lineNo {0};
for (string line; std::getline(ifs, line); ++lineNo)
{
input->push_back(line);
std::istringstream line_stream(line);
for (string text, word; line_stream >> text; word.clear())
{
std::remove_copy_if(text.begin(), text.end(),
std::back_inserter(word), ispunct);
auto& nos = result[word];
if (!nos) nos.reset(new std::set<StrBlob::size_type>);
nos->insert(lineNo);
}
}
}
QueryResult TextQuery::query(const string& str) const
{
static shared_ptr<std::set<StrBlob::size_type>> nodate(
new std::set<StrBlob::size_type>);
auto found = result.find(str);
if (found == result.end())
return QueryResult(str, nodate, input);
else
return QueryResult(str, found->second, input);
}
std::ostream& print(std::ostream& out, const QueryResult& qr)
{
out << qr.word << " occurs " << qr.nos->size()
<< (qr.nos->size() > 1 ? " times" : " time") << std::endl;
for (auto i : *qr.nos)
{
ConstStrBlobPtr p(*qr.input, i);
out << "\t(line " << i + 1 << ") " << p.deref() << std::endl;
}
return out;
}ex12_33.h
#ifndef CP5_ex12_33_h
#define CP5_ex12_33_h
#include "ex12_22.h"
using std::shared_ptr;
#include <iostream>
#include <fstream>
#include <map>
#include <set>
class QueryResult;
class TextQuery
{
public:
TextQuery(std::ifstream&);
QueryResult query(const string&) const;
private:
shared_ptr<StrBlob> input;
std::map<string, shared_ptr<std::set<StrBlob::size_type>>> result;
};
class QueryResult
{
public:
using ResultIter = std::set<StrBlob::size_type>::iterator;
friend std::ostream& print(std::ostream&, const QueryResult&);
public:
QueryResult(const string& s, shared_ptr<std::set<StrBlob::size_type>> set,
shared_ptr<StrBlob> v)
: word(s), nos(set), input(v)
{
}
ResultIter begin() const
{
return nos->begin();
}
ResultIter end() const
{
return nos->end();
}
shared_ptr<StrBlob> get_file() const
{
return input;
}
private:
string word;
shared_ptr<std::set<StrBlob::size_type>> nos;
shared_ptr<StrBlob> input;
};
std::ostream& print(std::ostream&, const QueryResult&);
#endif#include "ex12_33.h"
#include <sstream>
#include <algorithm>
TextQuery::TextQuery(std::ifstream& ifs) : input(new StrBlob)
{
StrBlob::size_type lineNo {0};
for (string line; std::getline(ifs, line); ++lineNo)
{
input->push_back(line);
std::istringstream line_stream(line);
for (string text, word; line_stream >> text; word.clear())
{
std::remove_copy_if(text.begin(), text.end(),
std::back_inserter(word), ispunct);
auto& nos = result[word];
if (!nos) nos.reset(new std::set<StrBlob::size_type>);
nos->insert(lineNo);
}
}
}
QueryResult TextQuery::query(const string& str) const
{
static shared_ptr<std::set<StrBlob::size_type>> nodate(
new std::set<StrBlob::size_type>);
auto found = result.find(str);
if (found == result.end())
return QueryResult(str, nodate, input);
else
return QueryResult(str, found->second, input);
}
std::ostream& print(std::ostream& out, const QueryResult& qr)
{
out << qr.word << " occurs " << qr.nos->size()
<< (qr.nos->size() > 1 ? " times" : " time") << std::endl;
for (auto it = qr.begin(); it != qr.end(); ++it)
{
ConstStrBlobPtr p(*qr.get_file(), *it);
out << "\t(line " << *it + 1 << ") " << p.deref() << std::endl;
}
return out;
}
版权声明：本文为博主原创文章，如果转载，请注明出处
《C++primer(第五版)》学习之路-第十二章：动态内存
标签：c++primer
原文地址：http://blog.csdn.net/libin1105/article/details/48751823
