View difference between Paste ID: bUB90WBg and 2F6BG2Lr

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 main.cpp
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 #include <cassert>
 #include <sstream>
 
 #include "ini.h"
 
 using namespace std;
 
 int main() {
     std::istringstream input{
         "[vegetables]\n"
         "potatoes=10\n"
         "onions=1 \n"
         "\n"
         "cucumbers=12\n"
         "\n"
         "[guests] \n"
         "guest1_name = Ivan Durak\n"
         "guest2_name =  Vasilisa Premudraya\n"
         "[guest black list]"};
     ini::Document doc = ini::Load(input);
 
     assert(doc.GetSectionCount() == 3);
     assert((doc.GetSection("vegetables"s)
             == ini::Section{
                 {"potatoes"s, "10"s},
                 {"onions"s, "1"s},
                 {"cucumbers"s, "12"s},
             }));
     assert((doc.GetSection("guests"s)
             == ini::Section{{"guest1_name"s, "Ivan Durak"s}, {"guest2_name"s, "Vasilisa Premudraya"s}}));
     assert((doc.GetSection("dragons"s) == ini::Section{}));
     assert((doc.GetSection("guest black list"s) == ini::Section{}));
 
     doc.AddSection("pets"s) = ini::Section{{"nasty"s, "rat"s}};
     assert(doc.GetSectionCount() == 4);
 }
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 ini.h
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 #include <iostream>
 #include <string>
 #include <unordered_map>
 
 namespace ini {
 
 using Section = std::unordered_map<std::string, std::string>;
 
 class Document {
 public:
     Section& AddSection(std::string name);
     const Section& GetSection(const std::string& name) const;
     std::size_t GetSectionCount() const;
 
 private:
     std::unordered_map<std::string, Section> sections_;
 };
 
 Document Load(std::istream& input);
 
 }
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 ini.cpp
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 #include "ini.h"
 
 using namespace std;
 
 namespace ini {
 
 Section& Document::AddSection(std::string name) {
         return sections_[name];
 }
 
 const Section& Document::GetSection(const std::string& name) const {
 
     static Section section_;
 
     if (!(sections_.end() == sections_.find(name))) {
         return sections_.at(name);
     } else {
         return section_;
     }
 }
 
 std::size_t Document::GetSectionCount() const {
     return sections_.size();
 }
 
 Document Load(std::istream& input) {
 
     Document result;
     Section* section;
 
     for (string str;
          getline(input, str);) {
 
         auto it = str.find_first_not_of(' ');
 
         if (str.npos == it) {
             continue;
         }
 
         str = str.substr(it);
 
         if (str[0] == '[') {
             auto section_ = str.substr(1, str.find(']') - 1);
             section = &result.AddSection(section_);
 
         } else {
             it = str.find('=');
 
             string name_ = str.substr(0, str.find_last_not_of(' ', it - 1) + 1);
             str = str.substr(str.find_first_not_of(' ', it + 1));
 
             string value_ = str.substr(0, str.find_last_not_of(' ') + 1);
             section->insert({name_,
                              value_ });
         }
     }
     return result;
 }
 
 }