Example Code

##include <iostream>

#include <iomanip>

#include <cmath>

using namespace std;

int main()

{

int n;

double approx_e;

double precise_e = 2.7182818284590452353602874713526624977572;

cout << fixed << setprecision(40);

do {

cout << "Enter the number of terms to evaluate after the first or -1 to end: ";

cin >> n;

approx_e = 1.0;

double lastTerm = 1.0;

for (int i=1; i<=n; i++) {

double nextTerm = lastTerm/i;

approx_e += nextTerm;

lastTerm = nextTerm;

}

cout << "\ne is approximately " << approx_e << endl;

cout << "error is " << 100*fabs(precise_e - approx_e)/precise_e << "%\n\n";

} while (n > 0);

} 

#include <iostream>

#include <algorithm>

#include <array>

#include <iterator>

#include <iomanip>

using namespace std;

double randDouble() {

static int i = 0;

if (i++ < 80)

return (drand48()*100000);

else return 0.0000000000000001;

}

int main()

{

srand48(time(NULL));

array<double, 100> dArr;

double sum = 0.0;

double runningAvg = 0.0;

cout << fixed << setprecision(40);

generate(dArr.begin(), dArr.end(), randDouble);

cout << "Calculating average of array values with 2 different methods ..." <<

endl;

for (auto iter=dArr.begin(); iter != dArr.end(); ++iter) {

int i = iter - dArr.begin() + 1;

sum += *iter;

runningAvg += (*iter - runningAvg)/i;

cout << "After " << i << " numbers:\n";

cout << "\t" << runningAvg << " (running avg. method)\n";

cout << "\t" << sum/i << " (sum method)\n";

cout << "\t\t(sum = " << sum << " , sum method)\n";

}

}