How do you convert a list to a paragraph with a comma separating each item in the list?

Answer 1

The following example shows one possible solution using C++.

The list_to_csv function performs the initial conversion, converting a given list to a comma-separated values (CSV) string. Thus the list {a, b, c} would become the string "a, b, c".

The list_to_paragraph function takes a list, converts it to a CSV and then formats the CSV for output using "and" or "or" for the final element. Thus the list {a, b, c} becomes "a, b and c" or "a, b or c" depending on the and_or value (with "and" being the default).

Note the paragraph is not terminated with a period or a new line character since it would be useful to include the paragraph in another string which may itself be a paragraph. This is demonstrated by the print_list helper function which prints a given list in both "and" and "or" variants as part of two larger paragraphs (in this case just a single-line paragraph).

Finally, the main function tests the program, starting with an empty list and building up to a list of 4 elements, printing each in turn.

#include<iostream>

#include<list>

#include<sstream>

enum class and_or {and, or};

std::string list_to_csv (const std::list<std::string>& list) {

std::stringstream ss;

auto it=list.cbegin();

while (it!=list.cend())

{

ss << *it++;

if (it!=list.cend())

ss << ", ";

}

return ss.str();

}

std::string list_to_paragraph (std::string csv, const and_or andor = and_or::and) {

size_t pos = csv.find_last_of(',');

if (pos != std::string::npos)

{

csv.replace(pos, 1, " ");

csv.insert(pos+1, andor==and_or::and?"and":"or");

}

return csv;

}

void print_list (const std::list<std::string>& list) {

std::cout << "List of " << list.size() << " item(s): {" << csv_to_paragraph(list_to_csv(list), and_or::and) << "}\n";

std::cout << "List of " << list.size() << " item(s): {" << csv_to_paragraph(list_to_csv(list), and_or::or) << "}\n";

}

int main(){

std::list<std::string> list;

print_list (list);

list.push_back ("a");

print_list (list);

list.push_back ("b");

print_list (list);

list.push_back ("c");

print_list (list);

list.push_back ("d");

print_list (list);

}