Learning C++. printf() is messy

[the tree]

A couple of years back I made an attempt at learning C++. I'm now trying to take it back up, here is an attempt:

#include <stdio.h>
int main()
{
   int xo,xt,yo,yt;
   float grad;

   printf("Enter the first co-ordinate:\n");
   scanf("%d",&xo);
   scanf("%d",&yo);
   printf("And the second one:\n");
   scanf("%d",&xt);
   scanf("%d",&yt);
   grad = (yo-yt)/(xo-xt);
   printf("Chord of (%d",xo);printf(",%d",yo);printf(")");
   printf("  and (%d",xt);printf(",%d",yt);printf(")\n");
   printf("Gradient: %f",grad);

   scanf("%f",grad);
   return 0;
}

The issue I found was that it wouldn't work when I tried printf("string",variable,"string"); so I ended up having to do lots and lots of printf()s. Now I seem to remember another method of output that went something like

cout >>> "string" >>> variable;

But I can't remember how to do that.

[RyanJ]

I believe what you want is this:

 

#include <stdio.h>
int main()
{
   int xo,xt,yo,yt;
   float grad;

   printf("Enter the first co-ordinate:\n");
   scanf("%d",&xo);
   scanf("%d",&yo);
   printf("And the second one:\n");
   scanf("%d",&xt);
   scanf("%d",&yt);
   grad = (yo-yt)/(xo-xt);
   printf("Chord of (%d,%d)  and (%d,%d)\nGradient: %f", xo, yo, xt, yt, grad);
   scanf("%f",grad);
   return 0;
}

 

Or the cout way

 

#include <stdio.h>
#include <iostream.h>
int main()
{
   int xo,xt,yo,yt;
   float grad;

   printf("Enter the first co-ordinate:\n");
   scanf("%d",&xo);
   scanf("%d",&yo);
   printf("And the second one:\n");
   scanf("%d",&xt);
   scanf("%d",&yt);
   grad = (yo-yt)/(xo-xt);
   cout << "Chord of (" << xo << "," << yo ")  and (" << xt << "," << yt << ")\nGradient: " << grad;

   scanf("%f",grad);
   return 0;
}

 

Incase you are interested I have a few reference sites you may like too

 

http://www.cplusplus.com/doc/tutorial/

http://www.intap.net/~drw/cpp/

http://www.cprogramming.com/tutorial.html

 

And good luck learning C++!

 

Cheers,

 

Ryan Jones

[the tree]

Thanks, I guess I just hadn't got how printf() was meant to work.

 

What is the best way to end a program so it doesn't close until the user does something? My current method seems to cause crashage.

[RyanJ]

Thanks, I guess I just hadn't got how printf() was meant to work.

 

Actually it can be quite a confusing function

 

All you need to remember is that the order in which you add the replace tags is the order in which you add the stuff to replace them

 

Again good lcuk with learning C++ its a good language

 

Cheers,

 

Ryan Jones

[Dave]

I don't see why you're using scanf and printf when you have cin and cout? For example, you can clean pretty much everything up and dispense with stdio.h:

 

#include <iostream>

using namespace std; // you need this so that you don't have to do std::cout

int main()
{
   float xo,xt,yo,yt;
   float grad;

   cout << "Enter the first co-ordinate:" << endl;
   cin >> xo >> yo;
   cout << "And the second one:" << endl;
   cin >> xt >> yt;

   grad = (yo-yt)/(xo-xt);

   cout << "Chord of (" << xo << "," << yo << ")  and (" << xt << "," << yt << ")" << endl << "Gradient: " << grad << endl;

   return 0;
}

 

Note that the current standard says you should drop the '.h' at the end of standard include files. For instance, iostream.h -> iostream, string.h -> string etc.

 

I've changed your co-ordinates to be floats instead of ints, otherwise you won't get a proper value for the gradient. Also, you need the "using namespace std" since all of the standard streams like cout, cin are all kept in std (read up on namespaces). If you don't include that, you'll get undefined variable errors.

 

Hope this helps.

[RyanJ]

Thanks for pointing that out dave

 

I'm no expert at C++ (I know enough to get by and thats about it ). I do know about the cin command but I thought I had better leave it as the tree had started

 

Again thanks for pointing that out...

 

Cheers,

 

Ryan Jones

[the tree]

I don't see why you're using scanf and printf when you have cin and cout?

Really just because they were in the tutorial that came with this complier-thingumy.

[LOGIC]

What is the best way to end a program so it doesn't close until the user does something? My current method seems to cause crashage.

 

 

I think the best way is to put the following before return statement

 

system("PAUSE");

[the tree]

Thanks but it says that function is undeclared.

[RyanJ]

Thanks but it says that function is undeclared.

 

Did you include the correct library and define the function?

 

Have a look here

 

Cheers,

 

Ryan Jones

[LOGIC]

sorry I forgate to tell you about:-p

#include <stdlib.h>