以下是c++pirmer的文本查詢系統再探的源碼，基本部分沒有做什麼修改。編譯環境爲c-free5.0,已編譯通過。
這裏提幾個注意事項：
1.使用c++11特性的時候，在編譯環境裏增加指令-std=c++11.代碼中出現的shared_ptr、make_ptr原本是boost庫中的內容，已經被吸收到了c++標準庫中，引用頭文件memory即可。
2.如果在做15.34的練習的時候，編譯會出現Link error undefined reference to “vtable for XXX”的錯誤，這是因爲虛函數在鏈接的時候還沒有函數體，這時候還沒有定義eval函數。舉個例子比方下面的類，編譯就會出錯。
class Base
{
virtual void f() = 0;
}
class Derived : public Base
{
void f();
}
解決辦法是在類外定義一個函數體即可。
void Derived::f()
{}3.第三個也不算注意事項啦，程序需要前面一些練習作爲前提，這裏已經完成了。
另外，在使用line_no這個屬性的時候，提前聲明一下，似乎書中遺漏了這行代碼，會出現未定義的錯誤。
#include <string>
#include <vector>
#include <iostream>
#include <fstream>
#include <sstream>
#include <set>
#include <map>
#include <memory>
#include <algorithm>
using namespace std;
string make_plural(size_t ctr,const string& word,const string &end){
return (ctr==1)?word:word+end;
}
class QueryResult;
class TextQuery{
public:
using line_no=vector<string>::size_type;
TextQuery(ifstream&);
QueryResult query(const string&) const;
private:
shared_ptr<vector<string>> file;
map<string,shared_ptr<set<line_no>>> wm;
};
TextQuery::TextQuery(ifstream& is):file(new vector<string>){
string text;
while(getline(is,text)){
file->push_back(text);
int n=file->size()-1;
istringstream line(text);
string word;
while(line>>word){
auto &lines=wm[word];
if(!lines){
lines.reset(new set<line_no>);
}
lines->insert(n);
}
}
};
class QueryResult{
friend ostream& print(ostream&,const QueryResult&);
public:
using line_no=TextQuery::line_no;
using ResultIter=set<line_no>::iterator;
QueryResult(string s,
shared_ptr<set<line_no> > p,
shared_ptr<vector<string>> f):
sought(s),lines(p),file(f){}
shared_ptr<vector<string>> get_file()const {
return file;
}
ResultIter begin()const {
return lines->begin();
}
ResultIter end() const{
return lines->end();
}
private:
string sought;
shared_ptr<set<line_no> > lines;
shared_ptr<vector<string>> file;
};
QueryResult
TextQuery::query(const string&sought) const{
static shared_ptr<set<line_no>> nodata(new set<line_no>);
auto loc=wm.find(sought);
if(loc==wm.end())
return QueryResult(sought,nodata,file);
else
return QueryResult(sought,loc->second,file);
};
ostream &print(ostream& os,const QueryResult &qr){
os<<qr.sought<<"occur "<<qr.lines->size()<<" "
<<make_plural(qr.lines->size(),"times","s")<<endl;
for(auto num:*qr.lines){
os<<"\t(line"<<num+1<<")"
<<*(qr.file->begin()+num)<<endl;
}
return os;
}
class Query_base{
friend class Query;
protected:
using line_no=TextQuery::line_no;
virtual ~Query_base();
private:
virtual QueryResult eval(const TextQuery&)const =0;
virtual string rep()const=0;
} ;
Query_base::~Query_base(){
}
class Query{
friend Query operator~(const Query&);
friend Query operator|(const Query&,const Query&);
friend Query operator&(const Query&,const Query&);
public:
Query(const string&);
QueryResult eval(const TextQuery &t)const{
return q->eval(t);
cout<<"WordQuery eval"<<endl;
}
string rep()const{
cout<<"Query rep"<<endl;
return q->rep();
}
private:
Query(shared_ptr<Query_base> query):q(query){
}
shared_ptr<Query_base> q;
};
ostream &
operator<<(ostream &os,const Query &query){
return os<<query.rep();
}
class WordQuery:public Query_base{
friend class Query;
WordQuery(const string &s):query_word(s){
cout<<"WordQuery construct "<<s<<endl;
}
QueryResult eval(const TextQuery &t) const{
cout<<"WordQuery eval"<<endl;
return t.query(query_word);
}
string rep()const{
cout<<"WordQuery rep"<<endl;
return query_word;
}
string query_word;
};
inline Query::Query(const string &s):q(new WordQuery(s)){
cout<<"Query construct"<<s<<endl;
}
class NotQuery:public Query_base{
friend Query operator~(const Query &);
NotQuery(const Query&q):query(q){
cout<<"NotQuery construct"<<endl;
}
string rep()const{
return "~("+query.rep()+")";
}
QueryResult eval(const TextQuery&) const;
Query query;
};
inline Query operator~(const Query &operand){
return shared_ptr<Query_base>(new NotQuery(operand));
}
QueryResult
NotQuery::eval(const TextQuery& text)const{
auto result=query.eval(text);
auto ret_lines=make_shared<set<line_no>>();
auto beg=result.begin(),end=result.end();
auto sz=result.get_file()->size();
for(size_t n=0;n!=sz;++n){
if(beg==end||*beg!=n)
ret_lines->insert(n);
else if(beg!=end)
++beg;
}
return QueryResult(rep(),ret_lines,result.get_file());
}
class Binary_Query:public Query_base{
protected:
Binary_Query(const Query &l,const Query &r,string s):
lhs(l),rhs(r),opSym(s){
cout<<"Binary_Query construct"<<s<<endl;
}
string rep()const{
cout<<"Binary_Query rep"<<endl;
return "("+lhs.rep()+" "
+opSym+" "
+rhs.rep()+")";
}
Query lhs,rhs;
string opSym;
};
class AndQuery:public Binary_Query{
friend Query operator&(const Query&,const Query &);
AndQuery(const Query& l,const Query &r):
Binary_Query(l,r,"&"){
cout<<"AndQuery construct"<<endl;
}
QueryResult eval(const TextQuery&) const;
};
QueryResult AndQuery::eval(const TextQuery& text) const{
cout<<"AndQuery eval"<<endl;
auto left=lhs.eval(text),right=rhs.eval(text);
auto ret_lines=make_shared<set<line_no>>();
set_intersection(left.begin(),left.end(),
right.begin(),right.end(),
inserter(*ret_lines,ret_lines->begin()));
return QueryResult(rep(),ret_lines,left.get_file());
}
inline Query operator&(const Query &lhs,const Query &rhs){
return shared_ptr<Query_base>(new AndQuery(lhs,rhs));
}
class OrQuery:public Binary_Query{
friend Query operator|(const Query&,const Query &);
OrQuery(const Query& l,const Query &r):
Binary_Query(l,r,"|"){ cout<<"OrQuery construct"<<endl; }
QueryResult eval(const TextQuery&) const;
};
inline Query operator|(const Query &lhs,const Query &rhs){
return shared_ptr<Query_base>(new OrQuery(lhs,rhs));
}
QueryResult OrQuery::eval(const TextQuery& text) const{
cout<<"OrQuery eval"<<endl;
auto right=rhs.eval(text),left=lhs.eval(text);
auto ret_lines=
make_shared<set<line_no>>(left.begin(),left.end());
ret_lines->insert(right.begin(),right.end());
return QueryResult(rep(),ret_lines,left.get_file());
}
int main(){
Query q=Query("fiery")&Query("bird")|Query("wind");
cout<<q;
return 0;
}