new file: ex19_18.cpp

	new file:   ex19_20.cpp

Author: icecity96

ch19/ex19_18.cpp

@@ -0,0 +1,23 @@
+#include <iostream>
+#include <algorithm>
+#include <string>
+#include <functional>
+#include <vector>
+
+int main(int argc, char *argv[])
+{
+	std::vector< std::string > v;
+	std::string a;
+	while (std::getline(std::cin,a)) {
+		v.push_back(a);	
+	}
+	auto m = std::count_if(v.begin(),v.end(),std::mem_fn(&std::string::empty));
+	std::cout << "Using mem_fun,the number of empty lines:" << m << std::endl;
+	auto n = std::count_if(v.begin(),v.end(),std::bind(&std::string::empty,std::placeholders::_1));
+	std::cout << "Using bind,the number of empty lines:" << n << std::endl;
+	auto q = std::count_if(v.begin(),v.end(),[](std::string &tem){
+			return tem.empty();
+			});
+	std::cout << "Using lamba,the number of empty lines:" << q << std::endl;
+	return 0;
+}

ch19/ex19_20.cpp

@@ -0,0 +1,77 @@
+#include <iostream>
+#include <vector>
+#include <string>
+#include <fstream>
+#include <memory>
+#include <map>
+#include <set>
+#include <sstream>
+class TextQuery {
+	public:
+		class QueryResult;
+		using line_no = std::vector<std::string>::size_type;
+		TextQuery(std::ifstream&);
+		TextQuery::QueryResult query(const std::string&) const;
+	private:
+		std::shared_ptr<std::vector<std::string> > file;
+		std::map<std::string, std::shared_ptr<std::set<line_no> > > wm;	
+};
+
+class TextQuery::QueryResult{
+	friend std::ostream& print(std::ostream&, const QueryResult&);
+	public:
+		QueryResult(std::string s, std::shared_ptr<std::set<line_no> > p,
+				std::shared_ptr<std::vector<std::string> > f):sought(s),lines(p),file(f){};
+	private:
+		std::string sought; //query word
+		std::shared_ptr<std::set<line_no> > lines; //lines the word show
+		std::shared_ptr<std::vector<std::string> > file; //files show the word;
+};
+
+TextQuery::TextQuery(std::ifstream &is) : file(new std::vector<std::string> ){
+	std::string text;
+	while (getline(is, text)) {
+		file->push_back(text);	
+		int n = file->size() - 1;
+		std::istringstream line(text);	
+		std::string word;
+		while (line >> word) {
+			auto &lines = wm[word];	
+			if (!lines) {
+				lines.reset(new std::set<line_no>);	
+			}
+			lines->insert(n);
+		}
+	}
+}
+
+TextQuery::QueryResult
+TextQuery::query(const std::string &sought) const{
+	static std::shared_ptr<std::set<line_no> > nodata(new std::set<line_no>);
+	auto loc = wm.find(sought);
+	if (loc == wm.end()) {
+		return TextQuery::QueryResult(sought, nodata, file);		
+	}
+	else {
+		return TextQuery::QueryResult(sought,loc->second,file);
+	}
+}
+
+std::ostream &print (std::ostream & os, const TextQuery::QueryResult & qr)
+{
+	os << qr.sought << " occurls " << qr.lines->size() << " time(s)" << std::endl; 
+	for (auto i : *qr.lines) {
+		os << "\t(line " << i+1 << ") " << *(qr.file->begin() + i) << std::endl;	
+	}
+	return os;
+}
+
+int main(int argc, char *argv[])
+{
+	std::ifstream file;
+	file.open("ex19_18.cpp");
+	TextQuery si(file);
+	auto res = si.query("std");
+	print(std::cout, res);
+	return 0;
+}