diff options
Diffstat (limited to 'c++.html.markdown')
| -rw-r--r-- | c++.html.markdown | 263 |
1 files changed, 160 insertions, 103 deletions
diff --git a/c++.html.markdown b/c++.html.markdown index 4113d5f4..176ea1a8 100644 --- a/c++.html.markdown +++ b/c++.html.markdown @@ -72,13 +72,13 @@ void func(); // function which may accept any number of arguments int* ip = nullptr; // C standard headers are available in C++. -// C headers end in .h, while +// C headers end in .h, while // C++ headers are prefixed with "c" and have no ".h" suffix. // The C++ standard version: #include <cstdio> -//The C standard version: +// The C standard version: #include <stdio.h> int main() @@ -257,7 +257,7 @@ fooRef = bar; cout << &fooRef << endl; //Still prints the address of foo cout << fooRef; // Prints "I am bar" -//The address of fooRef remains the same, i.e. it is still referring to foo. +// The address of fooRef remains the same, i.e. it is still referring to foo. const string& barRef = bar; // Create a const reference to bar. @@ -553,10 +553,14 @@ Point Point::operator+(const Point& rhs) const return Point(x + rhs.x, y + rhs.y); } +// It's good practice to return a reference to the leftmost variable of +// an assignment. `(a += b) == c` will work this way. Point& Point::operator+=(const Point& rhs) { x += rhs.x; y += rhs.y; + + // `this` is a pointer to the object, on which a method is called. return *this; } @@ -657,7 +661,7 @@ printMessage<10>(); // Prints "Learn C++ faster in only 10 minutes!" // The standard library provides a few exception types // (see http://en.cppreference.com/w/cpp/error/exception) -// but any type can be thrown an as exception +// but any type can be thrown as an exception #include <exception> #include <stdexcept> @@ -757,7 +761,7 @@ failure: // things are a little cleaner, but still sub-optimal. void doSomethingWithAFile(const char* filename) { - FILE* fh = fopen(filename, "r"); // Open the file in read mode + FILE* fh = fopen(filename, "r"); // Open the file in shared_ptrread mode if (fh == nullptr) throw std::runtime_error("Could not open the file."); @@ -809,7 +813,154 @@ void doSomethingWithAFile(const std::string& filename) // all automatically destroy their contents when they fall out of scope. // - Mutexes using lock_guard and unique_lock -// containers with object keys of non-primitive values (custom classes) require + +///////////////////// +// Smart Pointer +///////////////////// + +// Generally a smart pointer is a class, which wraps a "raw pointer" (usage of "new" +// respectively malloc/calloc in C). The goal is to be able to +// manage the lifetime of the object being point to without explicitly deleting +// the object. The term itself simply describes a set of pointers with the +// mentioned abstraction. +// Basically smart pointers should preferred over raw pointers, to prevent +// risky memory leaks, which happens if you forget to delete the object. + +// Usage of a raw pointer: +Dog* ptr = new Dog(); +ptr->bark(); +delete ptr; + +// With the usage of smart pointers you dont have to worry about the deletion +// of a object anymore. +// A smart pointer describes a policy, to count the references on the +// pointer. As matter of fact the objects gets destroyed when the last +// reference on the object gets destroyed. + +// Usage of "std::shared_ptr": +void foo() +{ +// Its not longer necessary to delete the Dog. +std::shared_ptr<Dog> doggo(new Dog()); +doggo->bark(); +} + +// Beware of possible circular references!!! +// There will be always a reference, so it will be never destroyed! +std::shared_ptr<Dog> doggo_one (new Dog()); +std::shared_ptr<Dog> doggo_two (new Dog()); +doggo_one = doggo_two; // p1 references p2 +doggo_two = doggo_one; // p2 references p1 + +// As mentioned before there is a set of smart pointers. The way you have to +// use it, is always the same. +// This leads us to question, when to use which one? +// std::unique_ptr - use it when you just want to hold one reference on +// the same object. +// std::shared_ptr - use it when you want to hold multiple references on the +// same object and want to make sure that it´s de-allocated +// when all refences are gone. +// std::weak_ptr - use it when you want to hold multiple references from +// different places for references for which it´s no problem +// tp de-allocate. + + +///////////////////// +// Containers +///////////////////// + +// Containers or the Standard Template Library are some predefined templates. +// They manage the storage space for its elements and provide +// member functions to access and manipulate them. + +// Few containers are as follows: + +// Vector (Dynamic array) +// Allow us to Define the Array or list of objects at run time +#include <vector> +string val; +vector<string> my_vector; // initialize the vector +cin >> val; +my_vector.push_back(val); // will push the value of 'val' into vector ("array") my_vector +my_vector.push_back(val); // will push the value into the vector again (now having two elements) + +// To iterate through a vector we have 2 choices: +// Either classic looping (iterating through the vector from index 0 to its last index): +for (int i = 0; i < my_vector.size(); i++) { + cout << my_vector[i] << endl; // for accessing a vector's element we can use the operator [] +} + +// or using an iterator: +vector<string>::iterator it; // initialize the iterator for vector +for (it = my_vector.begin(); it != my_vector.end(); ++it) { + cout << *it << endl; +} + +// Set +// Sets are containers that store unique elements following a specific order. +// Set is a very useful container to store unique values in sorted order +// without any other functions or code. + +#include<set> +set<int> ST; // Will initialize the set of int data type +ST.insert(30); // Will insert the value 30 in set ST +ST.insert(10); // Will insert the value 10 in set ST +ST.insert(20); // Will insert the value 20 in set ST +ST.insert(30); // Will insert the value 30 in set ST +// Now elements of sets are as follows +// 10 20 30 + +// To erase an element +ST.erase(20); // Will erase element with value 20 +// Set ST: 10 30 +// To iterate through Set we use iterators +set<int>::iterator it; +for(it=ST.begin();it<ST.end();it++) { + cout << *it << endl; +} +// Output: +// 10 +// 30 + +// To clear the complete container we use Container_name.clear() +ST.clear(); +cout << ST.size(); // will print the size of set ST +// Output: 0 + +// NOTE: for duplicate elements we can use multiset +// NOTE: For hash sets, use unordered_set. They are more efficient but +// do not preserve order. unordered_set is available since C++11 + +// Map +// Maps store elements formed by a combination of a key value +// and a mapped value, following a specific order. + +#include<map> +map<char, int> mymap; // Will initialize the map with key as char and value as int + +mymap.insert(pair<char,int>('A',1)); +// Will insert value 1 for key A +mymap.insert(pair<char,int>('Z',26)); +// Will insert value 26 for key Z + +// To iterate +map<char,int>::iterator it; +for (it=mymap.begin(); it!=mymap.end(); ++it) + std::cout << it->first << "->" << it->second << '\n'; +// Output: +// A->1 +// Z->26 + +// To find the value corresponding to a key +it = mymap.find('Z'); +cout << it->second; + +// Output: 26 + +// NOTE: For hash maps, use unordered_map. They are more efficient but do +// not preserve order. unordered_map is available since C++11. + +// Containers with object keys of non-primitive values (custom classes) require // compare function in the object itself or as a function pointer. Primitives // have default comparators, but you can override it. class Foo { @@ -822,12 +973,13 @@ struct compareFunction { return a.j < b.j; } }; -//this isn't allowed (although it can vary depending on compiler) -//std::map<Foo, int> fooMap; +// this isn't allowed (although it can vary depending on compiler) +// std::map<Foo, int> fooMap; std::map<Foo, int, compareFunction> fooMap; fooMap[Foo(1)] = 1; fooMap.find(Foo(1)); //true + /////////////////////////////////////// // Lambda Expressions (C++11 and above) /////////////////////////////////////// @@ -994,101 +1146,6 @@ cout << get<3>(concatenated_tuple) << "\n"; // prints: 15 cout << get<5>(concatenated_tuple) << "\n"; // prints: 'A' -///////////////////// -// Containers -///////////////////// - -// Containers or the Standard Template Library are some predefined templates. -// They manage the storage space for its elements and provide -// member functions to access and manipulate them. - -// Few containers are as follows: - -// Vector (Dynamic array) -// Allow us to Define the Array or list of objects at run time -#include <vector> -string val; -vector<string> my_vector; // initialize the vector -cin >> val; -my_vector.push_back(val); // will push the value of 'val' into vector ("array") my_vector -my_vector.push_back(val); // will push the value into the vector again (now having two elements) - -// To iterate through a vector we have 2 choices: -// Either classic looping (iterating through the vector from index 0 to its last index): -for (int i = 0; i < my_vector.size(); i++) { - cout << my_vector[i] << endl; // for accessing a vector's element we can use the operator [] -} - -// or using an iterator: -vector<string>::iterator it; // initialize the iterator for vector -for (it = my_vector.begin(); it != my_vector.end(); ++it) { - cout << *it << endl; -} - -// Set -// Sets are containers that store unique elements following a specific order. -// Set is a very useful container to store unique values in sorted order -// without any other functions or code. - -#include<set> -set<int> ST; // Will initialize the set of int data type -ST.insert(30); // Will insert the value 30 in set ST -ST.insert(10); // Will insert the value 10 in set ST -ST.insert(20); // Will insert the value 20 in set ST -ST.insert(30); // Will insert the value 30 in set ST -// Now elements of sets are as follows -// 10 20 30 - -// To erase an element -ST.erase(20); // Will erase element with value 20 -// Set ST: 10 30 -// To iterate through Set we use iterators -set<int>::iterator it; -for(it=ST.begin();it<ST.end();it++) { - cout << *it << endl; -} -// Output: -// 10 -// 30 - -// To clear the complete container we use Container_name.clear() -ST.clear(); -cout << ST.size(); // will print the size of set ST -// Output: 0 - -// NOTE: for duplicate elements we can use multiset -// NOTE: For hash sets, use unordered_set. They are more efficient but -// do not preserve order. unordered_set is available since C++11 - -// Map -// Maps store elements formed by a combination of a key value -// and a mapped value, following a specific order. - -#include<map> -map<char, int> mymap; // Will initialize the map with key as char and value as int - -mymap.insert(pair<char,int>('A',1)); -// Will insert value 1 for key A -mymap.insert(pair<char,int>('Z',26)); -// Will insert value 26 for key Z - -// To iterate -map<char,int>::iterator it; -for (it=mymap.begin(); it!=mymap.end(); ++it) - std::cout << it->first << "->" << it->second << '\n'; -// Output: -// A->1 -// Z->26 - -// To find the value corresponding to a key -it = mymap.find('Z'); -cout << it->second; - -// Output: 26 - -// NOTE: For hash maps, use unordered_map. They are more efficient but do -// not preserve order. unordered_map is available since C++11. - /////////////////////////////////// // Logical and Bitwise operators ////////////////////////////////// |