Mixing
If statements in a do while loop with a yes or no ending
Clash Royale CLAN TAG#URR8PPP
up vote
13
down vote
favorite
I am new to coding and I'm trying to do a long do while loop with nested if statements but I'm having issues with getting my loop to actually loop.
Instead of getting help directly on my project, which has a very long code, I made a simple kind of like it version. It also does not loop. It will get to the end and ask the user if they want to try again but when "y" is entered it ignores the if statements.
#include <iostream>
#include <string>
using namespace std;
int main()
string sodaChoice;
char answer = 'n';
do
cout << "Please choose your favorite soda from the following: Rootbeer, Diet Coke, Coke, Sprite" << "n";
getline(cin, sodaChoice);
if (sodaChoice == "Rootbeer")
cout << "Me too!" << "n";
else if (sodaChoice == "Diet")
cout << "Not me :(" << "n";
else if (sodaChoice == "Coke")
cout << "It's alright" << "n";
else if (sodaChoice == "Sprite")
cout << "only if I'm sick" << "n";
else
cout << "That was not on the list";
cout << "would you like to try again?";
cin >> answer;
while (answer == 'y'
I thought maybe I needed a do loop in the do loop around the if statements but then I didn't know how to go about it. Any help would be appreciated. I have spent many, many hours trying to figure it out.
I tried to ask my teacher, but my college teaches from some generic curriculum that their dean wrote based on her book. He is not very enthusiastic about helping or teaching.
c++ if-statement do-while
edited 8 mins ago
svick
167k39283400
asked 7 hours ago
JKisa
694
New contributor
JKisa is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
add a comment |Â
up vote
13
down vote
favorite
I am new to coding and I'm trying to do a long do while loop with nested if statements but I'm having issues with getting my loop to actually loop.
Instead of getting help directly on my project, which has a very long code, I made a simple kind of like it version. It also does not loop. It will get to the end and ask the user if they want to try again but when "y" is entered it ignores the if statements.
#include <iostream>
#include <string>
using namespace std;
int main()
string sodaChoice;
char answer = 'n';
do
cout << "Please choose your favorite soda from the following: Rootbeer, Diet Coke, Coke, Sprite" << "n";
getline(cin, sodaChoice);
if (sodaChoice == "Rootbeer")
cout << "Me too!" << "n";
else if (sodaChoice == "Diet")
cout << "Not me :(" << "n";
else if (sodaChoice == "Coke")
cout << "It's alright" << "n";
else if (sodaChoice == "Sprite")
cout << "only if I'm sick" << "n";
else
cout << "That was not on the list";
cout << "would you like to try again?";
cin >> answer;
while (answer == 'y'
I thought maybe I needed a do loop in the do loop around the if statements but then I didn't know how to go about it. Any help would be appreciated. I have spent many, many hours trying to figure it out.
I tried to ask my teacher, but my college teaches from some generic curriculum that their dean wrote based on her book. He is not very enthusiastic about helping or teaching.
c++ if-statement do-while
edited 8 mins ago
svick
167k39283400
asked 7 hours ago
JKisa
694
New contributor
JKisa is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
3
Although please remove the second, off-topic question :P
– Lightness Races in Orbit
7 hours ago
I have no idea what's happening, but it works perfectly for me. Besides,
– user202729
7 mins ago
std::cin ignores spaces by default.
– user202729
5 mins ago
add a comment |Â
up vote
13
down vote
favorite
up vote
13
down vote
favorite
I am new to coding and I'm trying to do a long do while loop with nested if statements but I'm having issues with getting my loop to actually loop.
Instead of getting help directly on my project, which has a very long code, I made a simple kind of like it version. It also does not loop. It will get to the end and ask the user if they want to try again but when "y" is entered it ignores the if statements.
#include <iostream>
#include <string>
using namespace std;
int main()
string sodaChoice;
char answer = 'n';
do
cout << "Please choose your favorite soda from the following: Rootbeer, Diet Coke, Coke, Sprite" << "n";
getline(cin, sodaChoice);
if (sodaChoice == "Rootbeer")
cout << "Me too!" << "n";
else if (sodaChoice == "Diet")
cout << "Not me :(" << "n";
else if (sodaChoice == "Coke")
cout << "It's alright" << "n";
else if (sodaChoice == "Sprite")
cout << "only if I'm sick" << "n";
else
cout << "That was not on the list";
cout << "would you like to try again?";
cin >> answer;
while (answer == 'y'
I thought maybe I needed a do loop in the do loop around the if statements but then I didn't know how to go about it. Any help would be appreciated. I have spent many, many hours trying to figure it out.
I tried to ask my teacher, but my college teaches from some generic curriculum that their dean wrote based on her book. He is not very enthusiastic about helping or teaching.
c++ if-statement do-while
edited 8 mins ago
svick
167k39283400
asked 7 hours ago
JKisa
694
New contributor
JKisa is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
I am new to coding and I'm trying to do a long do while loop with nested if statements but I'm having issues with getting my loop to actually loop.
Instead of getting help directly on my project, which has a very long code, I made a simple kind of like it version. It also does not loop. It will get to the end and ask the user if they want to try again but when "y" is entered it ignores the if statements.
#include <iostream>
#include <string>
using namespace std;
int main()
string sodaChoice;
char answer = 'n';
do
cout << "Please choose your favorite soda from the following: Rootbeer, Diet Coke, Coke, Sprite" << "n";
getline(cin, sodaChoice);
if (sodaChoice == "Rootbeer")
cout << "Me too!" << "n";
else if (sodaChoice == "Diet")
cout << "Not me :(" << "n";
else if (sodaChoice == "Coke")
cout << "It's alright" << "n";
else if (sodaChoice == "Sprite")
cout << "only if I'm sick" << "n";
else
cout << "That was not on the list";
cout << "would you like to try again?";
cin >> answer;
while (answer == 'y'
I thought maybe I needed a do loop in the do loop around the if statements but then I didn't know how to go about it. Any help would be appreciated. I have spent many, many hours trying to figure it out.
I tried to ask my teacher, but my college teaches from some generic curriculum that their dean wrote based on her book. He is not very enthusiastic about helping or teaching.
c++ if-statement do-while
c++ if-statement do-while
edited 8 mins ago
svick
167k39283400
asked 7 hours ago
JKisa
694
New contributor
JKisa is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
edited 8 mins ago
svick
167k39283400
asked 7 hours ago
JKisa
694
New contributor
JKisa is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
edited 8 mins ago
svick
167k39283400
edited 8 mins ago
svick
167k39283400
edited 8 mins ago
svick
167k39283400
167k39283400
asked 7 hours ago
JKisa
694
New contributor
JKisa is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
asked 7 hours ago
JKisa
694
asked 7 hours ago
JKisa
694
694
New contributor
JKisa is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
New contributor
JKisa is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
JKisa is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
3
Although please remove the second, off-topic question :P
– Lightness Races in Orbit
7 hours ago
I have no idea what's happening, but it works perfectly for me. Besides,
– user202729
7 mins ago
std::cin ignores spaces by default.
– user202729
5 mins ago
add a comment |Â
3
Although please remove the second, off-topic question :P
– Lightness Races in Orbit
7 hours ago
I have no idea what's happening, but it works perfectly for me. Besides,
– user202729
7 mins ago
std::cin ignores spaces by default.
– user202729
5 mins ago
3
3
Although please remove the second, off-topic question :P
– Lightness Races in Orbit
7 hours ago
Although please remove the second, off-topic question :P
– Lightness Races in Orbit
7 hours ago
I have no idea what's happening, but it works perfectly for me. Besides,
– user202729
7 mins ago
I have no idea what's happening, but it works perfectly for me. Besides,
– user202729
7 mins ago
std::cin ignores spaces by default.
– user202729
5 mins ago
std::cin ignores spaces by default.
– user202729
5 mins ago
add a comment |Â
4 Answers
4
active
oldest
votes
up vote
11
down vote
With
cin >> answer;
you read exactly one character. The problem is that you entered at least two characters when writing the answer. The actual 'y' or 'n' plus the Enter key, which is added as a newline in the input buffer.
This newline is then read by the next getline call as an empty line.
There are a few solutions to this problem, for example using ignore after reading into answer. Or if you want only one-word inputs then you could use formatted input using >> for sodaChoice too, since it will by default skip leading white-space (like newlines).
answered 7 hours ago
Some programmer dude
285k24233392
I don't think so, stackoverflow.com/questions/52717083/…
– user202729
4 mins ago
add a comment |Â
up vote
5
down vote
Existing answers are correct in the case of the user behaving nicely and entering just a 'y' or an 'n' followed by a newline.
We can add a little safety with a modification to the .ignore() call by asking it to ignore all characters up to an including the next newline:
You will need to add this header include at the top of your translation unit:
#include <limits>
And you'll need to add this line before cin >> answer:
// consumes and ignores as many characters as necessary until a newline.
// The newline is also consumed.
cin.ignore(std::numeric_limits<std::streamsize>::max(), 'n');
Full program with test inputs here:
http://coliru.stacked-crooked.com/a/996e77559590ad6d
Unfortunately, it's not unusual for Computer Science teachers to know nothing about computer science. Don't worry about this or let it put you off learning how to write software - it's just a symptom of the fact that good software engineers get paid a lot more than good teachers.
Here is some useful reference material: https://en.cppreference.com/w/cpp/io/basic_istream/ignore
answered 7 hours ago
Richard Hodges
54.6k55698
add a comment |Â
up vote
3
down vote
I'm going to suggest something entirely the opposite of the other answers. Instead of using cin.ignore to skip any extra characters after the one you read, I think it's better to do all your reading with getline() and forget about cin >> somevar completely.
There are two reasons:
The formatted input you get with
cin >> somevarignores leading whitespace, including newlines. If the user hits Enter on an empty line the program doesn't do anything, but still expects further input. This is not what the user of a CLI program expects! The usual expectation is that Enter completes the input, and an empty input should either cause the program to use a default value, or to complain about invalid input. Withcin >> somevar, you can't do either.Formatted input leaves any unmatched input in the buffer. In your example, reading a single character leaves at least the following newline, but the same happens with other kinds of input. Reading a number (with
int i; cin >> i;) leaves anything after the number waiting for the next input operation, so entering123 abcwill return123, and theabcwill appear on the next input operation.The underlying cause of this is that by default, a command-line terminal is in a line-based mode. The program or the library functions don't see any input from the operating system until a complete line is entered. (
cin.ignore()can of course help you deal with this, but not with the first point.)
Using getline() matches the underlying mechanic exactly, lets you deal with empty inputs (as well as telling the difference between a zero, and a non-number when reading to an int), and automatically deals with the trailing garbage. You'll have to convert the read string manually to whatever it is you actually want, though.
In your case, you could change the loop condition trivially to something like this:
string answer;
...
getline(cin, answer);
} while (answer == "y" || answer == "Y");
If you need a number, you can use e.g. int num = std::stoi(str).
(In C, the same happens if using scanf() for user input, and similarly, it's better to use fgets() and then parse the string with sscanf(), which gives the same options but deals with line-buffering. I'm not too familiar with C++, so I can't tell how to have the exact equivalent of cin >> somevar with a full line read by getline().)
answered 4 hours ago
ilkkachu
3,302317
add a comment |Â
up vote
0
down vote
Since you are taking input from the user of type char but every Enter key hit, it assigns the newline (n) to the variable answer.
You can ignore this by adding a line just after the input line
cin.ignore();
You may read this for more details.
answered 7 hours ago
Shravan40
4,06221531
add a comment |Â
4 Answers
4
active
oldest
votes
4 Answers
4
active
oldest
votes
active
oldest
votes
active
oldest
votes
up vote
11
down vote
With
cin >> answer;
you read exactly one character. The problem is that you entered at least two characters when writing the answer. The actual 'y' or 'n' plus the Enter key, which is added as a newline in the input buffer.
This newline is then read by the next getline call as an empty line.
There are a few solutions to this problem, for example using ignore after reading into answer. Or if you want only one-word inputs then you could use formatted input using >> for sodaChoice too, since it will by default skip leading white-space (like newlines).
answered 7 hours ago
Some programmer dude
285k24233392
I don't think so, stackoverflow.com/questions/52717083/…
– user202729
4 mins ago
add a comment |Â
up vote
11
down vote
With
cin >> answer;
you read exactly one character. The problem is that you entered at least two characters when writing the answer. The actual 'y' or 'n' plus the Enter key, which is added as a newline in the input buffer.
This newline is then read by the next getline call as an empty line.
There are a few solutions to this problem, for example using ignore after reading into answer. Or if you want only one-word inputs then you could use formatted input using >> for sodaChoice too, since it will by default skip leading white-space (like newlines).
answered 7 hours ago
Some programmer dude
285k24233392
I don't think so, stackoverflow.com/questions/52717083/…
– user202729
4 mins ago
add a comment |Â
up vote
11
down vote
up vote
11
down vote
With
cin >> answer;
you read exactly one character. The problem is that you entered at least two characters when writing the answer. The actual 'y' or 'n' plus the Enter key, which is added as a newline in the input buffer.
This newline is then read by the next getline call as an empty line.
There are a few solutions to this problem, for example using ignore after reading into answer. Or if you want only one-word inputs then you could use formatted input using >> for sodaChoice too, since it will by default skip leading white-space (like newlines).
answered 7 hours ago
Some programmer dude
285k24233392
With
cin >> answer;
you read exactly one character. The problem is that you entered at least two characters when writing the answer. The actual 'y' or 'n' plus the Enter key, which is added as a newline in the input buffer.
This newline is then read by the next getline call as an empty line.
There are a few solutions to this problem, for example using ignore after reading into answer. Or if you want only one-word inputs then you could use formatted input using >> for sodaChoice too, since it will by default skip leading white-space (like newlines).
answered 7 hours ago
Some programmer dude
285k24233392
edited 7 hours ago
answered 7 hours ago
Some programmer dude
285k24233392
answered 7 hours ago
Some programmer dude
285k24233392
answered 7 hours ago
Some programmer dude
285k24233392
285k24233392
I don't think so, stackoverflow.com/questions/52717083/…
– user202729
4 mins ago
add a comment |Â
I don't think so, stackoverflow.com/questions/52717083/…
– user202729
4 mins ago
I don't think so, stackoverflow.com/questions/52717083/…
– user202729
4 mins ago
I don't think so, stackoverflow.com/questions/52717083/…
– user202729
4 mins ago
add a comment |Â
up vote
5
down vote
Existing answers are correct in the case of the user behaving nicely and entering just a 'y' or an 'n' followed by a newline.
We can add a little safety with a modification to the .ignore() call by asking it to ignore all characters up to an including the next newline:
You will need to add this header include at the top of your translation unit:
#include <limits>
And you'll need to add this line before cin >> answer:
// consumes and ignores as many characters as necessary until a newline.
// The newline is also consumed.
cin.ignore(std::numeric_limits<std::streamsize>::max(), 'n');
Full program with test inputs here:
http://coliru.stacked-crooked.com/a/996e77559590ad6d
Unfortunately, it's not unusual for Computer Science teachers to know nothing about computer science. Don't worry about this or let it put you off learning how to write software - it's just a symptom of the fact that good software engineers get paid a lot more than good teachers.
Here is some useful reference material: https://en.cppreference.com/w/cpp/io/basic_istream/ignore
answered 7 hours ago
Richard Hodges
54.6k55698
add a comment |Â
up vote
5
down vote
Existing answers are correct in the case of the user behaving nicely and entering just a 'y' or an 'n' followed by a newline.
We can add a little safety with a modification to the .ignore() call by asking it to ignore all characters up to an including the next newline:
You will need to add this header include at the top of your translation unit:
#include <limits>
And you'll need to add this line before cin >> answer:
// consumes and ignores as many characters as necessary until a newline.
// The newline is also consumed.
cin.ignore(std::numeric_limits<std::streamsize>::max(), 'n');
Full program with test inputs here:
http://coliru.stacked-crooked.com/a/996e77559590ad6d
Unfortunately, it's not unusual for Computer Science teachers to know nothing about computer science. Don't worry about this or let it put you off learning how to write software - it's just a symptom of the fact that good software engineers get paid a lot more than good teachers.
Here is some useful reference material: https://en.cppreference.com/w/cpp/io/basic_istream/ignore
answered 7 hours ago
Richard Hodges
54.6k55698
add a comment |Â
up vote
5
down vote
up vote
5
down vote
Existing answers are correct in the case of the user behaving nicely and entering just a 'y' or an 'n' followed by a newline.
We can add a little safety with a modification to the .ignore() call by asking it to ignore all characters up to an including the next newline:
You will need to add this header include at the top of your translation unit:
#include <limits>
And you'll need to add this line before cin >> answer:
// consumes and ignores as many characters as necessary until a newline.
// The newline is also consumed.
cin.ignore(std::numeric_limits<std::streamsize>::max(), 'n');
Full program with test inputs here:
http://coliru.stacked-crooked.com/a/996e77559590ad6d
Unfortunately, it's not unusual for Computer Science teachers to know nothing about computer science. Don't worry about this or let it put you off learning how to write software - it's just a symptom of the fact that good software engineers get paid a lot more than good teachers.
Here is some useful reference material: https://en.cppreference.com/w/cpp/io/basic_istream/ignore
answered 7 hours ago
Richard Hodges
54.6k55698
Existing answers are correct in the case of the user behaving nicely and entering just a 'y' or an 'n' followed by a newline.
We can add a little safety with a modification to the .ignore() call by asking it to ignore all characters up to an including the next newline:
You will need to add this header include at the top of your translation unit:
#include <limits>
And you'll need to add this line before cin >> answer:
// consumes and ignores as many characters as necessary until a newline.
// The newline is also consumed.
cin.ignore(std::numeric_limits<std::streamsize>::max(), 'n');
Full program with test inputs here:
http://coliru.stacked-crooked.com/a/996e77559590ad6d
Unfortunately, it's not unusual for Computer Science teachers to know nothing about computer science. Don't worry about this or let it put you off learning how to write software - it's just a symptom of the fact that good software engineers get paid a lot more than good teachers.
Here is some useful reference material: https://en.cppreference.com/w/cpp/io/basic_istream/ignore
answered 7 hours ago
Richard Hodges
54.6k55698
answered 7 hours ago
Richard Hodges
54.6k55698
answered 7 hours ago
Richard Hodges
54.6k55698
answered 7 hours ago
Richard Hodges
54.6k55698
54.6k55698
add a comment |Â
add a comment |Â
up vote
3
down vote
I'm going to suggest something entirely the opposite of the other answers. Instead of using cin.ignore to skip any extra characters after the one you read, I think it's better to do all your reading with getline() and forget about cin >> somevar completely.
There are two reasons:
The formatted input you get with
cin >> somevarignores leading whitespace, including newlines. If the user hits Enter on an empty line the program doesn't do anything, but still expects further input. This is not what the user of a CLI program expects! The usual expectation is that Enter completes the input, and an empty input should either cause the program to use a default value, or to complain about invalid input. Withcin >> somevar, you can't do either.Formatted input leaves any unmatched input in the buffer. In your example, reading a single character leaves at least the following newline, but the same happens with other kinds of input. Reading a number (with
int i; cin >> i;) leaves anything after the number waiting for the next input operation, so entering123 abcwill return123, and theabcwill appear on the next input operation.The underlying cause of this is that by default, a command-line terminal is in a line-based mode. The program or the library functions don't see any input from the operating system until a complete line is entered. (
cin.ignore()can of course help you deal with this, but not with the first point.)
Using getline() matches the underlying mechanic exactly, lets you deal with empty inputs (as well as telling the difference between a zero, and a non-number when reading to an int), and automatically deals with the trailing garbage. You'll have to convert the read string manually to whatever it is you actually want, though.
In your case, you could change the loop condition trivially to something like this:
string answer;
...
getline(cin, answer);
} while (answer == "y" || answer == "Y");
If you need a number, you can use e.g. int num = std::stoi(str).
(In C, the same happens if using scanf() for user input, and similarly, it's better to use fgets() and then parse the string with sscanf(), which gives the same options but deals with line-buffering. I'm not too familiar with C++, so I can't tell how to have the exact equivalent of cin >> somevar with a full line read by getline().)
answered 4 hours ago
ilkkachu
3,302317
add a comment |Â
up vote
3
down vote
I'm going to suggest something entirely the opposite of the other answers. Instead of using cin.ignore to skip any extra characters after the one you read, I think it's better to do all your reading with getline() and forget about cin >> somevar completely.
There are two reasons:
The formatted input you get with
cin >> somevarignores leading whitespace, including newlines. If the user hits Enter on an empty line the program doesn't do anything, but still expects further input. This is not what the user of a CLI program expects! The usual expectation is that Enter completes the input, and an empty input should either cause the program to use a default value, or to complain about invalid input. Withcin >> somevar, you can't do either.Formatted input leaves any unmatched input in the buffer. In your example, reading a single character leaves at least the following newline, but the same happens with other kinds of input. Reading a number (with
int i; cin >> i;) leaves anything after the number waiting for the next input operation, so entering123 abcwill return123, and theabcwill appear on the next input operation.The underlying cause of this is that by default, a command-line terminal is in a line-based mode. The program or the library functions don't see any input from the operating system until a complete line is entered. (
cin.ignore()can of course help you deal with this, but not with the first point.)
Using getline() matches the underlying mechanic exactly, lets you deal with empty inputs (as well as telling the difference between a zero, and a non-number when reading to an int), and automatically deals with the trailing garbage. You'll have to convert the read string manually to whatever it is you actually want, though.
In your case, you could change the loop condition trivially to something like this:
string answer;
...
getline(cin, answer);
} while (answer == "y" || answer == "Y");
If you need a number, you can use e.g. int num = std::stoi(str).
(In C, the same happens if using scanf() for user input, and similarly, it's better to use fgets() and then parse the string with sscanf(), which gives the same options but deals with line-buffering. I'm not too familiar with C++, so I can't tell how to have the exact equivalent of cin >> somevar with a full line read by getline().)
answered 4 hours ago
ilkkachu
3,302317
add a comment |Â
up vote
3
down vote
up vote
3
down vote
I'm going to suggest something entirely the opposite of the other answers. Instead of using cin.ignore to skip any extra characters after the one you read, I think it's better to do all your reading with getline() and forget about cin >> somevar completely.
There are two reasons:
The formatted input you get with
cin >> somevarignores leading whitespace, including newlines. If the user hits Enter on an empty line the program doesn't do anything, but still expects further input. This is not what the user of a CLI program expects! The usual expectation is that Enter completes the input, and an empty input should either cause the program to use a default value, or to complain about invalid input. Withcin >> somevar, you can't do either.Formatted input leaves any unmatched input in the buffer. In your example, reading a single character leaves at least the following newline, but the same happens with other kinds of input. Reading a number (with
int i; cin >> i;) leaves anything after the number waiting for the next input operation, so entering123 abcwill return123, and theabcwill appear on the next input operation.The underlying cause of this is that by default, a command-line terminal is in a line-based mode. The program or the library functions don't see any input from the operating system until a complete line is entered. (
cin.ignore()can of course help you deal with this, but not with the first point.)
Using getline() matches the underlying mechanic exactly, lets you deal with empty inputs (as well as telling the difference between a zero, and a non-number when reading to an int), and automatically deals with the trailing garbage. You'll have to convert the read string manually to whatever it is you actually want, though.
In your case, you could change the loop condition trivially to something like this:
string answer;
...
getline(cin, answer);
} while (answer == "y" || answer == "Y");
If you need a number, you can use e.g. int num = std::stoi(str).
(In C, the same happens if using scanf() for user input, and similarly, it's better to use fgets() and then parse the string with sscanf(), which gives the same options but deals with line-buffering. I'm not too familiar with C++, so I can't tell how to have the exact equivalent of cin >> somevar with a full line read by getline().)
answered 4 hours ago
ilkkachu
3,302317
I'm going to suggest something entirely the opposite of the other answers. Instead of using cin.ignore to skip any extra characters after the one you read, I think it's better to do all your reading with getline() and forget about cin >> somevar completely.
There are two reasons:
The formatted input you get with
cin >> somevarignores leading whitespace, including newlines. If the user hits Enter on an empty line the program doesn't do anything, but still expects further input. This is not what the user of a CLI program expects! The usual expectation is that Enter completes the input, and an empty input should either cause the program to use a default value, or to complain about invalid input. Withcin >> somevar, you can't do either.Formatted input leaves any unmatched input in the buffer. In your example, reading a single character leaves at least the following newline, but the same happens with other kinds of input. Reading a number (with
int i; cin >> i;) leaves anything after the number waiting for the next input operation, so entering123 abcwill return123, and theabcwill appear on the next input operation.The underlying cause of this is that by default, a command-line terminal is in a line-based mode. The program or the library functions don't see any input from the operating system until a complete line is entered. (
cin.ignore()can of course help you deal with this, but not with the first point.)
Using getline() matches the underlying mechanic exactly, lets you deal with empty inputs (as well as telling the difference between a zero, and a non-number when reading to an int), and automatically deals with the trailing garbage. You'll have to convert the read string manually to whatever it is you actually want, though.
In your case, you could change the loop condition trivially to something like this:
string answer;
...
getline(cin, answer);
} while (answer == "y" || answer == "Y");
If you need a number, you can use e.g. int num = std::stoi(str).
(In C, the same happens if using scanf() for user input, and similarly, it's better to use fgets() and then parse the string with sscanf(), which gives the same options but deals with line-buffering. I'm not too familiar with C++, so I can't tell how to have the exact equivalent of cin >> somevar with a full line read by getline().)
answered 4 hours ago
ilkkachu
3,302317
answered 4 hours ago
ilkkachu
3,302317
answered 4 hours ago
ilkkachu
3,302317
answered 4 hours ago
ilkkachu
3,302317
3,302317
add a comment |Â
add a comment |Â
up vote
0
down vote
Since you are taking input from the user of type char but every Enter key hit, it assigns the newline (n) to the variable answer.
You can ignore this by adding a line just after the input line
cin.ignore();
You may read this for more details.
answered 7 hours ago
Shravan40
4,06221531
add a comment |Â
up vote
0
down vote
Since you are taking input from the user of type char but every Enter key hit, it assigns the newline (n) to the variable answer.
You can ignore this by adding a line just after the input line
cin.ignore();
You may read this for more details.
answered 7 hours ago
Shravan40
4,06221531
add a comment |Â
up vote
0
down vote
up vote
0
down vote
Since you are taking input from the user of type char but every Enter key hit, it assigns the newline (n) to the variable answer.
You can ignore this by adding a line just after the input line
cin.ignore();
You may read this for more details.
answered 7 hours ago
Shravan40
4,06221531
Since you are taking input from the user of type char but every Enter key hit, it assigns the newline (n) to the variable answer.
You can ignore this by adding a line just after the input line
cin.ignore();
You may read this for more details.
answered 7 hours ago
Shravan40
4,06221531
answered 7 hours ago
Shravan40
4,06221531
answered 7 hours ago
Shravan40
4,06221531
answered 7 hours ago
Shravan40
4,06221531
4,06221531
add a comment |Â
add a comment |Â
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3
Although please remove the second, off-topic question :P
– Lightness Races in Orbit
7 hours ago
I have no idea what's happening, but it works perfectly for me. Besides,
– user202729
7 mins ago
std::cin ignores spaces by default.
– user202729
5 mins ago