C++,if project, how to calculate the slope of the line passing through them.

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The slope of the line is rise over run or (y2 - y1) / (x2 - x1). Enter value in the order of x1 y1 x2 y2 . do not calculate an undefined slope, ( just print the word "undefined" )

Example:

1 1 2 2 = 1
1 1 3 2 = 0.5
1 2 3 2 = 0
1 1 1 4 = undefined

This question is from Algebra 1, i can solve this using calculator and graph on paper but i am trying to write this program in C++. by the way i am using Microsoft visual C++ i have just downloaded from their website.

i have done this so far on visual studio c++:
how can i print "undefined" if the slope is not valid.

C++

#include <iostream>
using namespace std;

int main()
{
        int x1, y1, x2, y2;
	cout << "enter x1: ";
	   cin >> x1;
	cout << "enter y1: ";
	   cin >> y1;
	cout << "enter x2: ";
	   cin >> x2;
	cout << "enter y2: ";
	   cin >> y2;
	
	cout << y2 - y1 / x2 - x1 << endl;
	

	system("pause");
	return 0;
}

Posted 22-Oct-13 15:47pm

danial khan

Updated 22-Oct-13 16:03pm

v2

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Comments

Ranjan.D 22-Oct-13 22:16pm

First of all you should know or ask your teacher for what values of x1 y1 x2 y2 the slope is invalid.

Printing "undefined" is easy as you could do with cout<<"undefined".

danial khan 22-Oct-13 22:24pm

i mean the value: x1=1 y1=1 x2=1 y2=4 calculate using this formula (y2 - y1) / (x2 - x1). comes 3/0 if 0 is denominator print "undefined".

danial khan 22-Oct-13 22:29pm

another example for 1 2 3 2 calculates using formula (y2 - y1) / (x2 - x1). comes 0/2 do not print the denominator just print numerator "0".

Member 10353629 23-Oct-13 1:03am

yes，you shuld ask your teacher!!

Ranjan.D 22-Oct-13 22:35pm

if (x2 - x1 == 0)
cout<<"undefined" << endl;
else
cout << y2 - y1 / x2 - x1 << endl;

I advise you to learn basics and code solutions. These are really really basic things of programming.

Sergey Alexandrovich Kryukov 22-Oct-13 22:39pm

Sorry, wrong answer. This is not the only (and not the main "undefined" case). Do you need to learn basics by yourself? Look at my answer.
—SA

Ranjan.D 22-Oct-13 22:43pm

It's fine, I don't have to recall line algorithm. I'm just helping the OP based on his requirement.

Sergey Alexandrovich Kryukov 22-Oct-13 23:00pm

Don't help if you can confuse inquirer. Please.
—SA

Ranjan.D 22-Oct-13 23:13pm

I'm not confusing any one. All I code as per the requirement, sometimes I don't have to necessarily go , dig in line algorithm and understand about infinite derivatives. I just do my duty in helping peoples on my time. If peoples start arguing and proving we will spoil ourselves and this should not happen. Remember we are not here to prove anything, we are just helping hands. Sometimes we may go wrong, doesn't mean we are confusing peoples.

Sergey Alexandrovich Kryukov 23-Oct-13 0:30am

Look, I pointed out where your mistake is, and you are trying to defend your incorrect or incomplete answer. Why? After that, talking about "prof" and help is just demagogic. If you can help, help, but remember that not writing anything is much better than writing a mistaken answer.
—SA

danial khan 22-Oct-13 22:38pm

for you it is basic but for me it is not basic because i have just started C++ for the first time one week ago :)

Sergey Alexandrovich Kryukov 22-Oct-13 22:42pm

This has little to do with C++. You need to understand very basic school mathematics. If you are only starting with this level of elementary mathematics and learn programming in parallel.... hm... maybe this is good for you. Then it's even more important to focus on fundamental knowledge and theory...
—SA

Sergey Alexandrovich Kryukov 22-Oct-13 22:38pm

Frankly, off-topic. This is elementary school mathematics.
—SA

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Sergey Alexandrovich Kryukov · Answer 1 · 2013-10-22T16:38:00

Strictly speaking, it should be floating-point coordinates, but integers make the problem extremely simple. Floating-point values are approximate, and, these days, unfortunately, not so many people understand how to correctly work with them. Now, remember your Algebra 1, geometry, or whatever you learned, and think: what would make the problem of of drawing a line between two points indeterminate? Right, if two points have the same location, then you can draw infinite number of straight lines, from one point. So, you got one condition. There is another case: "infinite" derivative. This is when two x-coordinates are the same. In this case, if y-coordinates are different, you can draw a single straight line through two points, but this line would be vertical.

I would not worry that this line is vertical, because, the slope can be infinite (even though this case is not really covered by school algebra or even "elementary" calculus, but such thing can be formalized; the floating-point type even have special Inf values which you could assign to the result). The problem is that, with just two points, this infinite slope can be interpreted as either +Inf or −Inf, that is, this is an infinite case again. Note that this is the same very case where the integer division in your formula would give an exception. So, you can do another check for this case, or, too look cool :-), catch this exception and output your "underfined" when it is caught.

As this looks like a home assignment, no code samples for you. If you did not find out how to analyze this simplest mathematical problem, at least write the code with your own hands. I explained you 100% of what you need. And if you don't do such things with your own hands, you don't really learn; this simple idea has been proven on many examples.

Good luck,

—SA