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@TheMatt2
Last active Dec 25, 2020
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Example to show the speed difference of using an iterator across an array, versus using std::begin() iteration. Source: https://softwareengineering.stackexchange.com/questions/386614/c-iterator-why-is-there-no-iterator-base-class-all-iterators-inherit-from
/* Iterator Example
* Modified to support clang compiler
* Compiler and Run:
* $ clang++ -Wall -Ofast -std=c++11 iterator_test.cpp && ./a.out
* y
* y
* time1: 143ns
* time2: 168ns
* https://softwareengineering.stackexchange.com/questions/386614/c-iterator-why-is-there-no-iterator-base-class-all-iterators-inherit-from
*/
#include <chrono>
#include <iostream>
#include <algorithm>
template <class T>
class iterator_base {
public:
virtual T &operator*() = 0;
virtual iterator_base &operator++() = 0;
virtual bool operator==(iterator_base const &other) { return pos == other.pos; }
virtual bool operator!=(iterator_base const &other) { return pos != other.pos; }
iterator_base(T *pos) : pos(pos) {}
protected:
T *pos;
};
template <class T>
class array_iterator : public iterator_base<T> {
using iterator_base<T>::pos;
public:
virtual T &operator*() override { return *pos; }
virtual array_iterator &operator++() override { ++pos; return *this; }
array_iterator(T *pos) : iterator_base<T>(pos) {}
};
int main() {
char input[] = "asdfasdfasdfasdfasdfasdfasdfadsfasdqwerqwerqwerqrwertytyuiyuoiiuoThis is a stringy to search for something";
using namespace std::chrono;
auto start1 = high_resolution_clock::now();
auto pos = std::find(std::begin(input), std::end(input), 'g');
auto stop1 = high_resolution_clock::now();
std::cout << *++pos << "\n";
auto start2 = high_resolution_clock::now();
auto pos2 = std::find(array_iterator<char>(input), array_iterator<char>(input+sizeof(input)), 'g');
auto stop2 = high_resolution_clock::now();
std::cout << *++pos2 << "\n";
std::cout << "time1: " << duration_cast<nanoseconds>(stop1 - start1).count() << "ns\n";
std::cout << "time2: " << duration_cast<nanoseconds>(stop2 - start2).count() << "ns\n";
}
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