Simplification of appender function using std::accumulate-CodePudding

I wanted a simple function that takes a collection of strings and appends them and returns one string which is each string item appended together. I thought std::accumulate was the way to go but interested to hear if this code could be improved.

Is there a simpler append type function that can be used here instead of the lambda?

Is this overly complicated and best achieved by some other code?

#include <string>
#include <vector>
#include <iostream>
#include <numeric>

std::string concatenate(std::vector<std::string> strings)
{
    return std::accumulate(strings.begin(), strings.end(), std::string(""), [](std::string s1, std::string s2) { return s1   s2; });
}

int main() {
    std::vector<std::string> vec2{ "aaa","bbb","ccc","ddd","eee","fff" };
    std::cout << concatenate(vec2) << std::endl;
}

CodePudding user response：

Yes, you can omit the lambda entirely (or use std::plus<>{}).

Also the "" can be removed from std::string(""), or the whole third argument can be removed if you switch to std::reduce:

std::reduce(strings.begin(), strings.end());

Also concatenate should take the vector by a const reference, or even better a std::span<const std::string> (by value).

Also libfmt can be used for this:

fmt::format("{}", fmt::join(strings, ""));

CodePudding user response：

It can be simplified with C 17 fold expression, there is no an intermediate or a temporary collection needed.

#include <string>
#include <iostream>

template<typename ...S>
std::string concatenate(S&&... strings) {
    using namespace std::string_literals;
    return (""s   ...   strings);
}

int main() {
    std::cout << concatenate("aaa","bbb","ccc","ddd","eee","fff") << std::endl;
}