# _ Used in Python 3.6 and later.
n = 0
while(n<1_000_000_000):
    n+=1
print(n)

// ' Used in cpp 14 and later.
#include <iostream>
#include <string>
using namespace std;

// Demonstrates how chars and strings cannot be directly compared.
int main() {
    string strvar = "b";
    char charvar = 'b';

    cout << ('b' == charvar) << endl;
    cout << ("b" == strvar) << endl;
    // cout << ('a' == "a") << endl; // will error!

    return 0;
}

Performance Comparison: Speed of Python vs. C++

python

import time

# Start the timer
start_time = time.time()

n = 0
while n < 1_000_000_000:
    n += 1

# Stop the timer
end_time = time.time()

# Calculate the duration
duration = end_time - start_time

# Output the result and the time taken
print(f"Final value of n: {n}") ==> Final value of n: 1/000/000/000
print(f"Time taken: {duration:.4f} seconds") ==> Time taken: 99.2185 seconds

cpp

#include <iostream>
#include <chrono> // Include the chrono library for timing

using namespace std;
using namespace std::chrono; // Use the chrono namespace for convenience

int main()
{
    // Start the timer
    auto start = high_resolution_clock::now();

    int n = 0;
    while (n < 1'000'000'000)
        n++;

    // Stop the timer
    auto stop = high_resolution_clock::now();

    // Calculate the duration
    auto duration = duration_cast<milliseconds>(stop - start);

    // Output the result and the time taken
    cout << "Final value of n: " << n << endl; ==>Final value of n: 1/000/000/000
    cout << "Time taken: " << duration.count() << " milliseconds" << endl; ==>Time taken: 2334 milliseconds

    return 0;
}

As we noted earlier, algorithms require two important control structures: iteration and selection. Both of these are supported by Python in various forms. The programmer can choose the statement that is most useful for the given circumstance.

For repeating a block of code, C++ provides a standard while and for constructs. The while construct repeats a body of code as long as a condition is true. For example.

code python:

counter = 1
while counter <= 5: 
    print("Hello, world")
    counter += 1  

code cpp:

int counter = 1;
while (counter <= 5) {        

    cout << "Hello, world" << endl;
    counter = counter + 1;
}

Console output:
Hello, world
Hello, world
Hello, world
Hello, world
Hello, world

prints out the phrase “Hello, world” five times. The condition on the while statement is evaluated at the start of each repetition. If the condition is true, the body of the statement will execute.

The while statement is a very general purpose iterative structure that we will use in a number of different algorithms. In many cases, a compound condition will control the iteration. A fragment such as

while ((counter <= 10) && (!done)) {
...

would cause the body of the statement to be executed only in the case where both parts of the condition are satisfied due to the and operator (&&). The value of the variable counter would need to be less than or equal to 10 and the value of the variable done would need to be false (not false is true) so that true and true results in true.

Here are some of the logical operators that are useful for true-false boolean statements in C++.

and          - &&

or           - ||

not equal to - !=

not          - !

greater than - >

less than    - <

greater than
or equal to  - >=

less than
or equal to  - <=

These are the same as we saw in earlier chapters.

#include <iostream>
using namespace std;

int main(){
    int counter = 0;
    while (counter <= 1) {
        cout << "Hello, world!" << endl;
    }
};