I am writing a small program for my personal use to practice learning C++ and for its functionality, an MLA citation generator (I'm writing a large paper with tens of citations).
For lack of a better way to do it (I don't understand classes or using other .cpp files inside your main
, so don't bother telling me, I'll work on that when I have more time), I am writing a function for each type of citation. I might break this down into a function for each reused code if I get more time.
My question is: How does the std::cin
object work? I am currently reading in with std::cin >>
for the strings I expect to be single words and getline(std::cin, string)
for the strings with spaces. I am not getting the right output, though. I just want to know how std::cin
works and why I keep unexpectedly skipping over some inputs (for instance, it skips over webPage
instead of giving me a chance to input into it).
void webCit() {
std::cout << "Leave any unknowns blank.\n";
std::cout << "Author last name: ";
std::string lastName;
std::cin >> lastName;
if (lastName.size() != 0) {
lastName = lastName + ", ";
}
std::cout << "Author first name: ";
std::string firstName;
std::cin >> firstName;
if (firstName.size() != 0) {
firstName = firstName + ". ";
}
std::cout << "Article title: ";
std::string articleTitle;
getline(std::cin, articleTitle);
if (articleTitle.size() != 0) {
articleTitle = "\"" + articleTitle + ".\" ";
}
std::cout << "Title of web page: ";
std::string pageTitle;
std::cin >> pageTitle;
if (pageTitle.size() != 0) {
pageTitle = pageTitle + ". ";
}
std::cout << "Publication date: ";
std::string publicationDate;
getline(std::cin, publicationDate);
if (publicationDate.size() != 0) {
publicationDate = publicationDate + ". ";
}
std::cout << "Web address: ";
std::string webAddress;
getline(std::cin, webAddress);
webAddress = "<" + webAddress + ">. ";
std::cout << "Date accessed: ";
std::string dateAccessed;
getline(std::cin, dateAccessed);
if (dateAccessed.size() != 0) {
dateAccessed = dateAccessed + ". ";
}
std::string citation =
lastName + firstName + articleTitle + pageTitle + publicationDate + webAddress + dateAccessed;
std::cout << citation; // TEST; remove after
}
EDIT: I/O
Leave any unknowns blank.
Author last name: Doe
Author first name: John
Article title: Title of web page: title
Publication date: Web address: www.win.com
Date accessed: 4/29/09
Doe, John. Title. <www.win.com>. 4/29/09.
As you can see, something is going wrong, because my input is getting skipped over.
What is happening here is that std::cin >> firstName;
only reads up to but not including the first whitespace character, which includes the newline (or '\n'
) when you press enter, so when it gets to getline(std::cin, articleTitle);
, '\n'
is still the next character in std::cin
, and getline()
returns immediately.
// cin = "Bloggs\nJoe\nMan of Steel, Woman of Kleenex\n"
std::cin >> lastName;
std::cin >> firstName;
// firstName = "Joe", lastName = "Bloggs", cin = "\nMan of Steel, Woman of Kleenex\n"
getline(std::cin, articleTitle);
// articleTitle = "", cin = "Man of Steel, Woman of Kleenex\n"
Adding 'std::cin >> std::ws
' (ws
meaning whitespace) before your calls to getline()
fixes the problem:
std::cin >> firstName >> std::ws;
getline(std::cin, articleTitle);
But it is easier to see where you missed it if you do it in the argument:
std::cin >> firstName;
getline(std::cin >> std::ws, articleTitle);