Conditional Statement Simplification - C++

Question

What would the best way be of reducing my conditions in this code, is it to simply implement the Boost library for a string comparison or is there another way of doing it? I would much more prefer to avoid using boost if possible.

How could said question be implemented on the following code?

cout << " Please Enter An Answer Of Yes(Y) or No(N):";
string question; cin >> question;

if (question == "yes" || question == "Yes" || question == "Y" || question == "y" || question == "YEs" || question == "YES" || question == "yeS" || question == "yES") 
{
    cout << "You said yes!" << endl;
    return 1;
} 
else if (question == "No" || question == "NO" || question == "nO" || question == "N" || question == "n")
{
    cout << "You said no!" <<endl;
    return 0;
}  
else 
{
    AskAQuestion();
}

if ((question.size() > 0)&&(toupper(question[0] == ‘Y’)) cout << “you answered yes”; — Jeremy Friesner, Jul 10 '18 at 13:52
https://en.cppreference.com/w/cpp/string/byte/toupper There is a string version using std::transform in https://stackoverflow.com/questions/735204/convert-a-string-in-c-to-upper-case — Kenny Ostrom, Jul 10 '18 at 13:55
It could be construed as a sledgehammer to crack a nut solution, but I use std::regex for this kind of thing. — Bathsheba, Jul 10 '18 at 13:59
@JeremyFriesner: Do you really want "YOLO" to be an acceptable answer? — Lightness Races in Orbit, Jul 10 '18 at 13:59
seems it would be enough to check first character Y/N and to convert the case of it.no need to check all permutations — AndersK, Jul 10 '18 at 14:01
Do you have strcasecmp from POSIX? `if (!strcasecmp(question.c_str(), "yes"))` — KamilCuk, Jul 10 '18 at 14:01

NathanOliver · Answer 1 · 2018-07-10T14:03:18.467

It might not be the most efficent solution but if you convert the entire string to lower case then you only need to check against the word and the letter instead of all the possible permutation. So if you have

void make_lowercase(std::string& data)
{
    std::transform(data.begin(), data.end(), data.begin(), ::tolower);
}

Then

cout << " Please Enter An Answer Of Yes(Y) or No(N):";
string question; cin >> question;

if (question == "yes" || question == "Yes" || question == "Y" || question == "y" || question == "YEs" || question == "YES" || question == "yeS" || question == "yES") 
//...

Becomes

cout << " Please Enter An Answer Of Yes(Y) or No(N):";
string question; 
cin >> question;
make_lowercase(question);

if (question == "yes" || question == "y")
//...

score 1 · Accepted Answer · answered Jul 10 '18 at 13:58

The following does not do exactly the same since you did not check 'yEs' as a possible case in the first if statement, but this is probably along the lines what you are looking for. It is based on lower casing the answer of the user first before checking the answer, to reduce the number of cases to check.

#include <algorithm>
#include <cctype>

...

std::cout << "Please Enter An Answer Of Yes(Y) or No(N): ";
std::string answer; std::cin >> answer;
std::transform(answer.begin(), answer.end(), answer.begin(), std::tolower);

if (answer == "yes" || answer == "y")
{
  std::cout << "You said yes!\n";
  return 1;
}
else if (answer == "no" || answer == "n")
{
  std::cout << "You said no!\n";
  return 0;
}
else
{
  AskAQuestion();
}

I took the liberty of renaming question to answer, seems more logical in this context.

Good solution and it doesn't rely on any external libraries, thanks. — TrevorLee, Jul 10 '18 at 14:04

Conditional Statement Simplification - C++

2 Answers2