goto_to_std-transform.cpp

// compile with
// g++ -o main -O3 -std=c++11 -Wall -Wextra -pedantic -Werror main.cpp
//
// run:
// main 1
// main 2
// main 3
// main 4
// main 5
// main 6

#include <algorithm>
#include <chrono>
#include <ctime>
#include <functional>
#include <iostream>
#include <iterator>
#include <numeric>
#include <string>
#include <vector>

using namespace std;

vector<int> squareVec1(vector<int> v)
{
    auto it = begin(v);
    loopBegin:
    if (it == end(v))
        goto loopEnd;
    *it = *it * *it;
    ++it;
    goto loopBegin;
    loopEnd:
    return v;
}

vector<int> squareVec2(vector<int> v)
{
    auto it = begin(v);
    while (it != end(v))
    {
        *it = *it * *it;
        ++it;
    }
    return v;
}

vector<int> squareVec3(vector<int> v)
{
    for (auto it = begin(v); it != end(v); ++it)
    {
        *it = *it * *it;
    }
    return v;
}

vector<int> squareVec4(vector<int> v)
{
    for (int& i : v)
    {
        i = i * i;
    }
    return v;
}

vector<int> squareVec5(vector<int> v)
{
    transform(begin(v), end(v), begin(v), [](int i)
    {
        return i*i;
    });
    return v;
}

template<typename Container, typename Functor>
Container transformCont(Container xs, Functor op)
{
    transform(begin(xs), end(xs), begin(xs), op);
    return xs;
}

vector<int> squareVec6(const vector<int>& v)
{
    return transformCont(v, [](int i)
    {
        return i*i;
    });
}

vector<int> squareVec7(const vector<int>& v)
{
    vector<int> result;
    result.reserve(v.size());
    return accumulate(begin(v), end(v), result,
                      [](vector<int>& acc, int i)
    {
        acc.push_back(i*i);
        return acc;
    });
}

vector<int> squareVecNTimes(vector<int> v, int n,
                            const string& version)
{
    function<vector<int>(const vector<int>&)> f;
    if (version=="1") f = squareVec1;
    else if (version=="2") f = squareVec2;
    else if (version=="3") f = squareVec3;
    else if (version=="4") f = squareVec4;
    else if (version=="5") f = squareVec5;
    else if (version=="6") f = squareVec6;
    else if (version=="7") f = squareVec7;
    else return v;
    vector<int> v2;
    for (int i = 0; i < n; ++i)
    {
        v[i % v.size()] = i;
        v2 = f(v);
    }
    return v2;
}

int main(int argc, char *argv[])
{
    if (argc < 2)
        return 1;

    vector<int> v(10000);
    generate(begin(v), end(v), rand);

    typedef chrono::time_point<std::chrono::system_clock> Time;

    Time startTime = chrono::system_clock::now();

    vector<int> v2 = squareVecNTimes(v, 50000, argv[1]);

    Time endTime = chrono::system_clock::now();
    chrono::duration<double> elapsed_seconds = endTime - startTime;

    cout << argv[1] << ": "
         << accumulate(begin(v2), end(v2), 0)
         << " - elapsed time: " << elapsed_seconds.count() << "s\n";
}