Whenever I input a variable using cin, after one hits enter it automatically goes to a new line. I'm curious if there's a way to use cin without having it go to a new line. I'm wanting to cin and cout multiple things on the same line in the command prompt. Is this possible?
You can't use cin or any other standard input for this. But it is certainly possible to get the effect you are going for. I see you're on Windows using Visual Studio, so you can use, for example, _getch. Here's an example that reads until the next whitespace and stores the result in a string.
#include <conio.h> // for _getch
std::string get_word()
{
std::string word;
char c = _getch();
while (!std::isspace(c))
{
word.push_back(c);
std::cout << c;
c = _getch();
}
std::cout << c;
return word;
}
It's not very good. For example, it doesn't handle non printing character input very well. But it should give you an idea of what you need to do. You might also be interested in the Windows API keyboard functions.
If you want a wider audience, you will want to look into some cross-platform libraries, like SFML or SDL.
you can also use space for input instead of enter
something like this:
cin >> a >> b >> c;
and in input you type
10 20 30
then
a=10
b=20
c=30
As others have noted, you can't do this with cin, but you could do it with getchar(). What you would have to do is:
collect each character individually using getchar() (adding each to the end of a string as it is read in, for instance), then
after reading each character, decide when you've reached the end of one variable's value (e.g. by detecting one or more ' ' characters in the input, if you're reading in int or double values), then
if you've reached the end of the text for a variable, convert the string of characters that you've built into a variable of the appropriate type (e.g. int, double, etc.), then
output any content onto the line that might be required, and then
continue for the next variable that you're reading in.
Handling errors robustly would be complicated so I haven't written any code for this, but you can see the approach that you could use.
I don't think what you want to do can be achieved with cin. What you can do is to write all your input in one line, with a delimiter of your choosing, and parse the input string.
It is not possible. To quote #Bo Persson, it's not something controlled by C++, but rather the console window.
I can't comment but if you leave spaces between integers then you can get the desired effect. This works with cin too.
int a, b, c;
cin>>a; cin>>b; cin>>c;
If you enter your values as 10 20 30 then they will get stored in a, b, and c respectively.
just use the gotoxy statement. you can press 'enter' and input values in the same line
for eg. in the input of a 3*3 matrix:
#include<iostream.h>
#include<conio.h>
void main()
{clrscr();
int a[20][20],x,y;
cout<<"Enter the matrix:\n ";
for(int r=2;r<7;r+=2)
for(int c=2;c<7;c+=2)
{gotoxy(c,r);
cin>>a[r][c];
}
getch();}
Related
In C++, iostream automatically puts in a new line after cin. Is there a way to get rid of this?
I want use iomanip to format information into a table, like so:
cin cout
0.078125 3DA00000
-8.75 C10C0000
23.5 41BC0000
(random numbers)
example code:
#include <iostream>
using namespace std;
int main()
{
int num;
cin >> num; //now a new line.
cout << num << endl;
return 0;
}
You presumably pressed the return key to send your input from the command line to your program's standard input. That's where the newline is coming from. You can't read your number from cin before this newline appears in the console, because the newline is what causes the console to hand your input over to the program in the first place. You could, as a user, configure your console (or whatever is running your program) to act differently, but there's no way for the program itself to force such behavior.
If you really want to have your input and your output on the same line, you need to find a way to "write to the previous line". How that works depends on your console (see also How to rollback lines from cout?). There is no standard way to do this because cin and cout are in no way obligated to be attached to a console or anything resembling one, so it is not clear that "writing to the previous line" even means anything.
'endl' makes a new line just don't use it.
cout << num;
I have these 2 codes:
char a[256];
cin>>a;
cout<<a;
and
char a[256];
cin.get(a,256);cin.get();
cout<<a;
and maybe, relative to the second one without cin.get();
char a[256];
cin.get(a,256);
cout<<a;
My question is (first one) : for a char array, what should i use? cin or cin.get()? And why should i use cin.get(); with no parameter after my char initialisation?
And my second question is: my c++ teacher taught me to use every time cin.get() for initialisation chars and AFTER every initialisation char array or int array or just int or whatever, to again put cin.get(); after it. That's what i wanted to ask initially.
So, now i got these 2:
In this case, without cin.get() after the integer initialisation, my program will break and i can't do anymore my char initialisation.
int n;
cin>>n;
char a[256];
cin.get(a,256); cin.get(); // with or without cin.get();?
cout<<a;
And the correct one:
int n;
cin>>n; cin.get();
char a[256];
cin.get(a,256); cin.get(); // again, with or without?
cout<<a;
So, what's the matter? Please someone explain for every case ! Thank you.
They do different things, so choose whichever does what you want, or the better alternatives given below.
The first cin>>a; reads a single word, skipping over any leading space characters, and stopping when it encounters a space character (which includes the end of the line).
The second cin.get(a,256);cin.get(); reads a whole line, then consumes the end-of-line character so that repeating this will read the next line. cin.getline(a,256) is a slightly neater way to do this.
The third cin.get(a,256) reads a whole line but leaves the end-of-line character in the stream, so that repeating this will give no more input.
In each case, you'll get some kind of ill behaviour if the input word/line is longer than the fixed-size buffer. For that reason, you should usually use a friendlier string type:
std::string a;
std::cin >> a; // single word
std::getline(std::cin, a); // whole line
The string will grow to accommodate any amount of input.
The problem, most likely, is in the way you enter the values later on. The cin.get() after every initialization is there to "grab" the newline character that gets put in the stream every time you press enter.
Say you start entering your values like this:
2
a b c d...
Assuming you have pressed enter after 2, the newline character was also put on the stream. When you call cin.get() after that, it will grab and discard the newline character, allowing the rest of your code to properly get the input.
To answer your first question, for an array, you should use cin.get instead of the overloaded operator >> cin>> as that would only grab a single word, and it would not limit the amount of characters grabbed, which could lead to an overflow and data corruptions / program crashing.
On the other hand, cin.get() allows you to specify the maximum number of characters read, preventing such bugs.
For a char array use cin.get() because it counts whitespace whereas cin does not. More importantly, cin.get() sets the maximum number of characters to read. For example:
char foo[25]; //set maximum number of characters
cout << "Please type in characters for foo" << endl;
cin.get(foo,25);
cout << ' ' << foo;
In this case, you can only type in 24 characters and a null terminator character \0.
I hope this answers your first question.
I would personally use a string.
Ok, just to be up front, this IS homework, but it isn't due for another week, and I'm not entirely sure the final details of the assignment. Long story short, without knowing what concepts he'll introduce in class, I decided to take a crack at the assignment, but I've run into a problem. Part of what I need to do for the homework is read individual characters from an input file, and then, given the character's position within its containing word, repeat the character across the screen. The problem I'm having is, the words in the text file are single words, each on a different line in the file. Since I'm not sure we'll get to use <string> for this assignment, I was wondering if there is any way to identify the end of the line without using <string>.
Right now, I'm using a simple ifstream fin; to pull the chars out. I just can't figure out how to get it to recognize the end of one word and the beginning of another. For the sake of including code, the following is all that I've got so far. I was hoping it would display some sort of endl character, but it just prints all the words out run together style.
ifstream fin;
char charIn;
fin.open("Animals.dat");
fin >> charIn;
while(!fin.eof()){
cout << charIn;
fin >> charIn;
}
A few things I forgot to include originally:
I must process each character as it is input (my loop to print it out needs to run before I read in the next char and increase my counter). Also, the length of the words in 'Animals.dat' vary which keeps me from being able to just set a number of iterations. We also haven't covered fin.get() or .getline() so those are off limits as well.
Honestly, I can't imagine this is impossible, but given the restraints, if it is, I'm not too upset. I mostly thought it was a fun problem to sit on for a while.
Why not use an array of chars? You can try it as follow:
#define MAX_WORD_NUM 20
#define MAX_STR_LEN 40 //I think 40 is big enough to hold one word.
char words[MAX_WROD_NUM][MAX_STR_LEN];
Then you can input a word to the words.
cin >> words[i];
The >> operator ignores whitespace, so you'll never get the newline character. You can use c-strings (arrays of characters) even if the <string> class is not allowed:
ifstream fin;
char animal[64];
fin.open("Animals.dat");
while(fin >> animal) {
cout << animal << endl;
}
When reading characters from a c-string (which is what animal is above), the last character is always 0, sometimes represented '\0' or NULL. This is what you check for when iterating over characters in a word. For example:
c = animal[0];
for(int i = 1; c != 0 && i < 64; i++)
{
// do something with c
c = animal[i];
}
Does anyone knows why C instruction is being reordered when cin cout and gets is used consecutively here?
I am using Dev-C++ 4.9.9.2.
#include<iostream>
using namespace std;
int main(){
char a[10],b;
for(;;){
cout<<"\ncin>>b:";
cin>>b;
cout<<"gets(a):";
gets(a);
cout<<"cout<<a<<b:"<<a<<" "<<b<<"\n\n";
}
}
I got an output like:
cin>>b:132
gets(a):cout<<a<<b:32 1
cin>>b:465
gets(a):cout<<a<<b:65 4
cin>>b:312242
gets(a):cout<<a<<b:12242 3
cin>>b:1
gets(a):cout<<a<<b: 1
cin>>b:
It seemed like some input for cin was passed in gets.. and it also appears that instructions were reordered like:
cin>>b;
gets(a);
cout<<"gets(a):";
instead of,
cin>>b;
cout<<"gets(a):";
gets(a);
cin>>b read just a character, leaving the rest of the input to be read by later input operation. So gets sill has something to read and don't block.
At the first cin >> b, there is no input available. You enter '132\n' (input from terminal is usually made line by line) in a buffer and just get the 1 out of it. gets reads the next characters 32 and the \n which terminates gets. It doesn't need to read something more from the terminal.
Nothing has been re-ordered.
your input from keyboard has been send only when you pressed enter. At that time, there have been enough data to execute the cin<<b, the following cout, then to complete the gets(a).
In others words, the execution of cin<<b is suspended to the reception of a char. But that char is not send to the program until you pressed 'Enter' (this is because of your terminal settings). When you press 'Enter', the first char is received by cin<<b and the remaining is buffered. cout executes, and when it is the turn of gets(a), the buffer delivers the remaining chars included the carriage return, so gets(a) completes as well, with the data you entered to complete the cin<<b instruction.
Try to simply press enter for the cin<<b to complete, then you'll see the cout, and then you will have the gets(a) waiting for your inputs.
While not really answering your question...
The idiomatic way in C++ would rather be to use getline. It's an accident of history that does not make it part of the iostream interface directly, but it really is the function to use for inputs.
Shameless plug from the website:
// getline with strings
#include <iostream>
#include <string>
int main () {
std::string str;
std::cout << "Please enter full name: ";
getline (std::cin,str);
std::cout << "Thank you, " << str << ".\n";
}
The main advantage of getline, in this version, is that it reads up until it encounters a line-ending character.
You can specify your own set of "line-ending" characters in the overload accepting a third parameter, to make it stop on commas or colons, for example.
The code isn't reordered, but std::cout is buffered so the string doesn't appear immediately on your display. Therefore gets(a) will be executed with the output still in the buffer.
You can add a <<flush after the output string to make cout flush it's buffer.
When you use std::cin, it knows how to tell std::cout to flush the buffer before the input starts, so you don't have to.
I'm trying to get input from user and give output until s/he presses 'n'. It doesn't seem to work. Is problem in scanf or cin.get? When I press y it just takes "tekrar" as an input, thus gives "y" as output and goes into a loop. Also, doesn't stop when i give n as tekrar input.
char cevap[300]="";
char tekrar='y';
while (tekrar!='n')
{
cin.get(cevap,300);
cout<<cevap<<endl;
cout<<"Again? (y/n)";
scanf("%c",&tekrar);
}
output:
Hello
Again? (y/n)
y
Again? (y/n)
y
Again? (y/n)
n
Again? (y/n)
n
...
Mixing the various input methods on istream (get, getline, operator>>) can be fraught with peril if you're not aware of which methods leave the delimiter character in the stream and which don't, and handle them accordingly.
In this case, get will read 300 characters of input or input up until the newline, whichever happens first. The newline will not be extracted, and so will remain in the stream. That means your call to scanf() will read the newline and stop, leaving the y or n you just typed in the stream.
There are several ways to reorganize this code to make it do what it seems like you want. This is one way:
#include <iostream>
#include <string>
using namespace std;
int main()
{
string cevap;
char tekrar='y';
while (tekrar!='n')
{
getline(cin,cevap);
cout<<cevap<<endl;
cout<<"Again? (y/n)";
tekrar = cin.get();
cin.ignore();
}
return 0;
}
This uses std::string and the non-member getline to read input in such a way as to not require you to be limited to 300 characters (not strictly speaking related to the question, but good practice usually). getline consumes and discards the delimiter, but get, used to read the continuation input, doesn't, so we discard it manually via ignore.
Use cin operator>> to read from stdin, instead of scanf:
string cevap;
char tekrar='y';
while (tekrar!='n')
{
getline(cin, cevap);
cout<<cevap<<endl;
cout<<"Again? (y/n)";
cin >> tekrar;
cin.get();
}
Edit: fixed the infinite loop. You should use std::string instead of a simple char array.