This is a follow-up question for A recursive_transform for std::vector with various return type and A recursive_transform for std::array with various return type. Based on these discussion about the recursive things, the another idea comes up in my mind that trying to implement a print function for arbitrary nested iterable things. Normally, the multiple for loops may be used for printing nested iterables. Maybe like this one.
std::vector<double> testVector1;
testVector1.push_back(1);
testVector1.push_back(20);
testVector1.push_back(-100);
decltype(testVector1) testVector2;
testVector2.push_back(10);
testVector2.push_back(90);
testVector2.push_back(-30);
std::vector<decltype(testVector1)> testVector3;
testVector3.push_back(testVector1);
testVector3.push_back(testVector2);
for (auto& outer_element : testVector3)
{
for (auto& inner_element : outer_element)
{
std::cout << inner_element << std::endl;
}
}
However, the multiple nested for loop shows up when it comes to the case like std::vector<std::vector<std::vector<std::vector<...>>>>.
If the structure similar to recursive_transform is used in this task, that's the recursive_print function here.
template<typename T>
concept is_iterable = requires(T x)
{
*std::begin(x);
std::end(x);
};
template<typename T>
concept is_elements_iterable = requires(T x)
{
std::begin(x)->begin();
std::end(x)->end();
};
template<class T> requires is_iterable<T>
T recursive_print(const T& input, const int level = 0)
{
T output = input;
std::cout << std::string(level, ' ') << "Level " << level << ":" << std::endl;
std::transform(input.cbegin(), input.cend(), output.begin(),
[level](auto& x)
{
std::cout << std::string(level, ' ') << x << std::endl;
return x;
}
);
return output;
}
template<class T> requires is_iterable<T> && is_elements_iterable<T>
T recursive_print(const T& input, const int level = 0)
{
T output = input;
std::cout << std::string(level, ' ') << "Level " << level << ":" << std::endl;
std::transform(input.cbegin(), input.cend(), output.begin(),
[level](auto& element)
{
return recursive_print(element, level + 1);
}
);
return output;
}
Here's a Godbolt link. The output of the example is as below. The nested level is also displaying with this recursive_print function.
Level 0:
Level 1:
Level 2:
1
20
-100
Level 2:
10
90
-30
Level 1:
Level 2:
1
20
-100
Level 2:
10
90
-30
All suggestions are welcome.
Which question it is a follow-up to?
A recursive_transform for std::vector with various return type and
A recursive_transform for std::array with various return type
What changes has been made in the code since last question?
The previous questions focus on the input/output content and type, but the print out operation is the main idea here.
Why a new review is being asked for?
If there is any possible improvement about this code, please let me know.
