Changes between Initial Version and Version 1 of code/howto/STL

Timestamp:

Oct 8, 2008, 2:17:39 AM (17 years ago)

Author:

landauf

Comment:

—

code/howto/STL

@@ +1 @@
+= HowTo: STL =
+[[TracNav(TracNav/TOC_Development)]]
+[[TOC]]
+
+== Overview ==
+|| '''vector''' || Like an array, every element has an index || Fast to access elements by position ||
+|| '''list''' || Elements are connected in a list, strictly ordered || Fast if you just want to store elements ||
+|| '''set''' || Comparable with a search-tree || Fast if you have to decide if an element is within the set or not ||
+|| '''map''' || Every element has a key || Fast if you have to find elements identified by a key ||
+
+== Usage ==
+=== vector ===
+{{{
+std::vector<type> myVector;
+
+type value1, value2, value3;
+myVector.push_back(value1);
+myVector.push_back(value2);
+myVector.push_back(value3);
+
+myVector[0]; // returns value1
+myVector[2]; // returns value3
+
+myVector.size(); // returns 3
+}}}
+
+== list ==
+{{{
+std::list<type> myList;
+
+type value1, value2, value3;
+myList.push_back(value1);
+myList.push_back(value2);
+myList.push_back(value3);
+
+
+// Iterate through all elements:
+for (std::list<type>::iterator = myList.begin(); it != myList.end(); ++it)
+{
+    std::cout << (*it) << std::endl;
+}
+
+// Output:
+// value1
+// value2
+// value3
+
+
+// Insert a new value at the beginning:
+type value4;
+myList.insert(myList.begin(), value4);
+}}}
+
+== set ==
+{{{
+std::set<type> mySet;
+
+type value1, value2, value3;
+mySet.insert(value1); //
+mySet.insert(value2); // Note: set has no order of the elements
+mySet.insert(value3); //
+
+
+// Tell if value2 is in the set:
+if (mySet.find(value2) != mySet.end())
+{
+    set::cout << value2 << " is in the set!" << std::endl;
+}
+
+
+// Iterate through all elements:
+for (std::set<type>::iterator = mySet.begin(); it != mySet.end(); ++it)
+{
+    std::cout << (*it) << std::endl;
+}
+
+// Output (set sorts elements from smaller to greater):
+// value1
+// value2
+// value3
+}}}
+
+=== map ===
+{{{
+std::map<std::string, type> myMap; // Note: map has two template arguments, key and type
+
+type value1, value2, value3;
+myMap["one"] = value1;
+myMap["two"] = value2;
+myMap["three"] = value3;
+
+
+// Tell if an element with key "two" is in the map:
+std::map<std::string, type>::iterator it = myMap.find("two");
+if (it != myMap.end())
+{
+    set::cout << "An element with key 'two' is in the set!" << std::endl;
+    std::cout << "The element is " << it->second << std::endl;
+}
+
+
+// Iterate through all elements:
+for (std::map<std::string, type>::iterator = myMap.begin(); it != myMap.end(); ++it)
+{
+    std::cout << it->first << ": " << it->second << std::endl;
+}
+
+// Output (map sorts keys from smaller to greater):
+// one: value1
+// three: value3
+// two: value2
+
+
+// Attention: operator[] adds an entry with defaultvalue:
+if (myMap["four"] != myMap.end())
+{
+    std::cout << "An element with key 'four' is in the set!" << std::endl;
+}
+// As we know, 'four' is NOT in the map. But after our call to myMap["four"] there
+// is now an empty entry for "four".
+//
+// If we iterate again through all elements, we get:
+//
+// Output (map sorts keys from smaller to greater):
+// four: 
+// one: value1
+// three: value3
+// two: value2
+//
+// Because this behaviour is usually unwanted, use find("four") like in the example above.
+}}}