2024-05-27-More on C++

The difference between C and C++

Compile in C but not in C++

References and Pointers

[[ 2024-05-27-Overloading and References#Reference ]]

Dynamic allocation

[[ 2024-05-27-Overloading and References#Dynamic Allocation in C++ ]]

Basic I/O in C++

Basic Library in C++

1. iostream: iostream stands for standard input-output stream. This header file contains definitions of objects like cin, cout, cerr, etc.
2. iomanip: iomanip stands for input-output manipulators. The methods declared in these files are used for manipulating streams. This file contains definitions of setw, setprecision, etc.
3. fstream: This header file mainly describes the file stream. This header file is used to handle the data being read from a file as input or data being written into the file as output.
4. bits/stdc++: This header file includes every standard library. In programming contests, using this file is a good idea, when you want to reduce the time wasted in doing chores; especially when your rank is time sensitive.

We can apply using namespace std to simplify the process of using standard library function in the std namespace.

Operators

1. Insertion operator <<
   The data needed to be displayed on the screen is inserted in cout using <<.
2. Extraction operator >>
   The extraction operator extracts data form the object cin to the place you have specified.
   Be aware the difference between redirection and insertion:
   2024-05-27-Interacting with user and systems

[!tip] Difference between std::endl and \n
std::endl:

It inserts a new line and flushes the stream immediately, which is used to achieve in-time interactions and avoid conflicts. But flush the stream is expensive, it is not suitable for many outputs to print.

\n

It will simply print a new line by just inserting a new line, which may be pushed into buffer instead of printing immediately.

Basic I/O stream

cin: standard input from keyboard -> stdin in C

1. using >> to take multiple inputs:
   cin >> name >> age;
   input can be:
   ABC
13
2. apply member function in the string buffer
   cin.getline(char *buffer, int N) Notice it will just read n-1 character and add a terminator at the end

cout: standard output to the display -> stdout in C

1. Using << to insert data to cout
   Notice we can insert multiple data to cout
   cout << "Name: << name << endl;
2. Implement member function
   cout.write(char* str, int n);

cerr: standard error output to display(unbuffered) -> stderr in C

Statement

Jump statements in C++

1. continue:
   It is used to execute the next iteration of the same loop while skipping the remaining part of the current condition.
2. break:
   It is used to terminate the whole loop if the condition is met.
3. return:
   It takes the control out of the function itself, used to terminate the entire function after execution of the function after some condition.
4. go to:
   It is used to jump directly to that part of the program to which is being called. Every goto statement is associated with a label.
   goto label_name;

Range-based for loop

#include <iostream>
#include <map>
#include <string>
#include <vector>
using namespace std;
int main()
{
    // Iterating over whole array
    vector<int> v = { 0, 1, 2, 3, 4, 5 };
    for (auto i : v)
        cout << i << ' ';
    cout << '\n';
    
    // the initializer may be a braced-init-list
    for (int n : { 0, 1, 2, 3, 4, 5 })
        cout << n << ' ';
    cout << '\n';
    
    // Iterating over array
    int a[] = { 0, 1, 2, 3, 4, 5 };
    for (int n : a)
        cout << n << ' ';
    cout << '\n';

    // Just running a loop for every array
    // element
    for (int n : a)
        cout << "In loop" << ' ';
    cout << '\n';

    // Printing string characters
    string str = "Geeks";
    for (char c : str)
        cout << c << ' ';
    cout << '\n';

    // Printing keys and values of a map
    map<int, int> MAP({ { 1, 1 }, { 2, 2 }, { 3, 3 } });
    for (auto i : MAP)
        cout << '{' << i.first << ", " << i.second << "}\n";
}

Exception handling in C++

Exception Type

1. Synchronous: Exceptions that happen when something goes wrong because of a mistake in the input data or when the program is not equipped to handle the current type of data it’s working with, such as dividing a number by zero.
2. Asynchronous: Exceptions that are beyond the program’s control, such as disc failure, keyboard interrupts, etc.

C++ try and catch

1. try in C++
   The try keyword represents a block of code that may throw an exception placed inside the try block. It’s followed by one or more catch blocks. If an exception occurs, try block throws that exception.

2. catch in C++
   The catch statement represents a block of code that is executed when a particular exception is thrown from the try block. The code to handle the exception is written inside the catch block.

3. throw in C++
   An exception in C++ can be thrown using the throw keyword. When a program encounters a throw statement, then it immediately terminates the current function and starts finding a matching catch block to handle the thrown exception.

Call by values and Call by references

[!Important] Difference between call by value and call by reference
Call by value

When calling a function, we pass the values of variables to it. In this method, the changes made to the dumpy variables in the called functions have no effects on the values of actual variables.

Call by Reference

When calling a function, we pass the address of variables to the function. In this method, the function could alter the values of the variables. It can be achieved with either pointer or references in C++