C++
Introduction
C \(\subset\) C++ are key programming languages that are still amongst the most commonly used. In fact, they are used in the creation of R and Python. One may have to return to C and C++ when speed and memory are limiting factors. Although we will not be programming in with these languages in our module (do not hand in ICAs using them), one should be aware of their existence, and not be afraid to explore them, especially when it seems like your code in R is running too slowly.
There are many ways to run and compile C++ programs on your computer. For example, you can try:
In addition, there are many resources and videos online. For example:
In particular, I did skim through the first YouTube video, on Saturday (9 Dec), and had no prior experience with C++ before that, and was able to write the code presented here using the C++ Online Shell.
Overview
One of the main differences between C++ and R is that you have to specify the data type: int (integer), double (floating point number), and string (text). Like Python, this is a general purpose language, so in order to do maths/stats one usually has to import libraries. In our example code, we revisit one of our first exercises.
Code: The average number of uniforms needed for its sum to exceed 1
// The average number of uniforms needed for its sum to exceed 1
#include <iostream> // standard library, almost needed for anything
using namespace std; // standard naming, commonly used, but debated whether one should use this
#include <string>
#include <random>
int sum() // notice we have to specify the type
{
random_device rd;
mt19937 gen(rd());
uniform_real_distribution<> dis(0, 1.0); // generating random variables (better than rand)
double T;
T=0;
int n;
n=0;
while (T<1) {
T= T+dis(gen);
n = n+1;
}
return n;
}
double repeater1(){
double x;
x=0;
int n; // the number of replicates to be inputed by the user
cout << "Type a number: "; // Type a number and press enter
cin >> n; // Get user input from the keyboard
for (int i = 0; i < n; ++i) { // the famous increment in C
x = x + sum();
}
double m;
m = x/n;
return m;
}
// the main function, is called by C++; it has to return an integer, but is used to run your code
int main(){
cout << repeater1();
cout << "\n"; // newline
cout << repeater1();
return 0;
}