Range Over Built in C++

For this example, we’ll translate the provided code to C++.

Range in C++ is typically done using iterators or range-based for loops. Here’s how the provided code would look in C++:

#include <iostream>
#include <vector>
#include <map>

int main() {
    // Summing numbers in a vector
    std::vector<int> nums = {2, 3, 4};
    int sum = 0;
    for (int num : nums) {
        sum += num;
    }
    std::cout << "sum: " << sum << std::endl;

    // Using index and value in a range-based loop
    for (size_t i = 0; i < nums.size(); ++i) {
        if (nums[i] == 3) {
            std::cout << "index: " << i << std::endl;
        }
    }

    // Iterating over a map
    std::map<std::string, std::string> kvs = {{"a", "apple"}, {"b", "banana"}};
    for (const auto& kv : kvs) {
        std::cout << kv.first << " -> " << kv.second << std::endl;
    }

    // Iterating only over the keys of the map
    for (const auto& kv : kvs) {
        std::cout << "key: " << kv.first << std::endl;
    }

    // Iterating over a string's characters
    std::string str = "go";
    for (size_t i = 0; i < str.size(); ++i) {
        std::cout << i << " " << static_cast<int>(str[i]) << std::endl;
    }

    return 0;
}

Here’s the detailed explanation adapted for C++:

Our first example uses a loop to sum the numbers in a vector. Arrays work like this too.

#include <iostream>
#include <vector>

int main() {
    std::vector<int> nums = {2, 3, 4};
    int sum = 0;
    for (int num : nums) {
        sum += num;
    }
    std::cout << "sum: " << sum << std::endl;
    return 0;
}

To run this program, put the code in main.cpp and compile it using a C++ compiler.

$ g++ -o main main.cpp
$ ./main
sum: 9

In the next example, we use a loop to print the indexes.

#include <iostream>
#include <vector>

int main() {
    std::vector<int> nums = {2, 3, 4};
    for (size_t i = 0; i < nums.size(); ++i) {
        if (nums[i] == 3) {
            std::cout << "index: " << i << std::endl;
        }
    }
    return 0;
}

To run this code, compile and execute in the same way as before.

To iterate over a map:

#include <iostream>
#include <map>

int main() {
    std::map<std::string, std::string> kvs = {{"a", "apple"}, {"b", "banana"}};
    for (const auto& kv : kvs) {
        std::cout << kv.first << " -> " << kv.second << std::endl;
    }
    return 0;
}

Also, you can iterate over just the keys of a map.

#include <iostream>
#include <map>

int main() {
    std::map<std::string, std::string> kvs = {{"a", "apple"}, {"b", "banana"}};
    for (const auto& kv : kvs) {
        std::cout << "key: " << kv.first << std::endl;
    }
    return 0;
}

Lastly, to iterate over the characters of a string and get their Unicode code points:

#include <iostream>
#include <string>

int main() {
    std::string str = "go";
    for (size_t i = 0; i < str.size(); ++i) {
        std::cout << i << " " << static_cast<int>(str[i]) << std::endl;
    }
    return 0;
}

Compile and run each of these examples using your C++ compiler to see the output. Now that we can run and build basic C++ programs, let’s learn more about the language.

Recursion in C++

Pointers in C++

Learn X By Example

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Range Over Built in C++