No idea whats wrong

[sandbox007]

Hi, I have two weird questions, not sure if its something wrong with my code...

1) Why is my output 0 ? shouldnt it be 11 divided by 100 multipied by 50 = 5.5?

  #include <iostream>
using namespace std;

int main()
{
	double x,a,b;
	a=50,b=60;
	
	x= 11/100*a;
	cout << x;
   
	return 0;
	
}

2)Why the program doesnt ask for me to cin the getline part? It only asks me to input x and then outputs "enter word" and thats it.... not sure whats the error but when i remove lines from int x; to cin>> x; . It works fine and would ask me to input my string.

#include <iostream>
#include <string>
using namespace std;

int main ()
{
int x;
cout<< "enter x :";
cin >> x;

string word;
cout << "enter word " <<endl;
getline(cin,word);
cout << word<< "\n";

return 0;
}

[seeplus]

1) 11 / 100 is an int / int which means that the result is an int (0). So 0 is then multipled by 50 to give 0. To give a float result for division, at least one of the numbers needs to be of type float

x = 11.0 / 100 * a;

2) stream extraction (cin) extracts up to a white-space char but doesn't extract that char. getline() extracts until a \n is found (or other terminating delim) and does extract and discard the delim. Hence the delim terminating the cin >> is the first char obtained for getline() which is a '\n' which terminates the getline!

This is a common issue when mixing >> and getline().

After the cin >> x then try inserting

cin.ignore();

which will ignore the next char (eg the \n).

[salem c]

> 1) Why is my output 0 ? shouldnt it be 11 divided by 100 multipied by 50 = 5.5?
11/100 is done in integer arithmetic, which will round down to 0.
This zero is then promoted to double, multiplied by a, leaving you with zero.

Write 11.0 / 100 * a to force the compiler to promote the division to double.

> 2)Why the program doesnt ask for me to cin the getline part?
It does.
The problem is mixing >> and getline is a trap.
You see, >> will leave the \n on the input stream, which getline immediately sees before you type anything.

Between >> and getline, you should call
https://en.cppreference.com/w/cpp/io/basic_istream/ignore

[rozick1]

On (1), you need to cast the 11 as a double:

x= (double)11/100 *a;

On (2), call

cin.ignore();

before getline.

[George P]

There are two ways resolve issues when mixing std::istream::operator>> and std::getline:

1. Use ignore, as others have shown.

2. Use std::ws as part of the extraction process with std::getline.
https://www.learncpp.com/cpp-tutorial/introduction-to-stdstring/

[Geckoo]

Hello. In our mind, when we divide an integer by an integer, we can get a floating number and all seems logical. For example, if I divide 3 by 2, I know that 1.5 is the result. However, for a computing system, if you divide an integer by an integer, you will get ... an integer - no more. In my previous example, you get 1. For this reason, you have to cast the values ++

x = (double(11)/double(100)) * a;

5.5

[lastchance]

Actually, you don't need to explicitly cast any of the values. You could just reorder as
x= 11*a/100;
since a is a double.

Personally I'd just write
x= 0.11*a;

However, for a computing system, if you divide an integer by an integer, you will get ... an integer - no more.

Well, that's true in C++/C and many languages and has been well and truly identified as the fault here. However, don't take it as gospel in all languages - in particular, it isn't true in Python, for example.

[Geckoo]

However, for a computing system, if you divide an integer by an integer, you will get ... an integer - no more.

Well, that's true in C++/C and many languages and has been well and truly identified as the fault here. However, don't take it as gospel in all languages - in particular, it isn't true in Python, for example.

Yes. I guess that many other languages compute numbers (including integers) in a different way.
Your comment is relevant and deserves to be noted. Well done ++