Keep running program and 'int' problem

I'm using this program in C++ to calculate wind chill:

Code:

---

#include <cstdlib>
#include <iostream>
#include <math.h>

using namespace std;

int main(int argc, char *argv[])
{
    cout << "Wind Chill Calculator...\n" ;
    cout << "By William Seed\n" ;
    int temp, vel;
    int ch;
    cout << "Enter the temperature:";
    cin >> temp;
    cout << "Enter the wind speed:";
    cin >> vel;
    ch = 35.75 + (.6215 * temp) - (35.75 * pow(vel,.16)) + (.4275 * temp * pow(vel,.16));
    cout << "The wind chill is: ";
    cout << ch;
    cout << "\n";
    system("PAUSE");
    return EXIT_SUCCESS;
}

---

I have two problems:

1. (most important) I want this program to keep running until I tell it to stop (using imput as yes or no.
2. If I try to use a decimal for 'temp', then the program ends...

I'm new, so no flaming, please.

Thanks in advance,

Will

Never mind about the second problem. I fixed it by declaring it a 'long double'.

Your temperature, windspeed and chill variables should all be double or float.
Since integers are whole numbers, using decimal points is inappropriate for the type int.

To keep the program running, you need to use some kind of loop. When you finish everything, ask the user if she wants to run the program again, if she enters yes, go back to the top of the loop, if she says no, terminate the loop.

It's up to you to figure out how to implement this.

Or use a sentinal controlled loop:

Code:

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std::cout << "Enter a number or enter -1 to end: ";
std::cin >> number;

while ( number != -1 )
{
  std::cout << "\nSqaured: " << number * number << std::endl;

  std::cout << "Enter a number or -1 to end: ";
  std::cin >> number;
}

---

This snippet will continue to square the number untill the user enters -1 to exit the loop

swgh I'm pretty sure this is his homework.

Oh sorry I did not complete the program for him I just mentioned a way to use a user controlled loop thats all.

Anyway, although the type of control swgh suggested can be useful, in my opinion there is a better loop for this case.
Also, you should be careful when using != and == with floating point numbers.

hi willrs2
here is what you need for your loop implementation:
http://www.cprogramming.com/tutorial/lesson3.html


1st: I'd suggest you to divide your code in contextual blocks, in order to make it more readable, for us and for you too.

2nd: if you need to print a line like

Code:

---

The wind chill is: <value>

---

You may put all these data into a single row of code:

Code:

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cout << "The wind chill is: " << ch << "\n";

---

3rd: <iostream> provides a useful "endl" (end line) to let you avoid typing "\n" everytime:

Code:

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cout << variable << endl;

---

just an example:
note the separated blocks of lines and where variable declarations should be put

Code:

---

int main(int argc, char *argv[])
{
    int temp, vel;
    int ch;

    cout << "Wind Chill Calculator...\n" ;
    cout << "By William Seed\n" ;

    cout << "Enter the temperature:";
    cin >> temp;

    cout << "Enter the wind speed:";
    cin >> vel;

    ch = 35.75 + (.6215 * temp) - (35.75 * pow(vel,.16)) + (.4275 * temp * pow(vel,.16));
    cout << "The wind chill is: " cout << ch << endl;

    system("PAUSE");
    return EXIT_SUCCESS;
}

---

Thanks, all of you. I used a while loop. Thanks carlorfeo for the tips, and thanks swgh and NeonBlack for the loop idea... I completely forgot about it...

Here is the code a the proggy working how I want it:

Code:

---

#include <cstdlib>
#include <iostream>
#include <math.h>

using namespace std;

int main(int argc, char *argv[])
{
    double temp, vel;
    double ch;
    char yn;
    while (yn = 1)
    {
          cout << "Wind Chill Calculator...\n" ;
          cout << "By William Seed\n" ;
          cout << "Enter the temperature: ";
          cin >> temp;
          cout << "Enter the wind speed: ";
          cin >> vel;
          ch = 35.75 + (.6215 * temp) - (35.75 * pow(vel,.16)) + (.4275 * temp * pow(vel,.16));
          cout << "The wind chill is: ";
          cout << ch;
          cout << "\n";
          cout << "Enter 1 to rerun program: " ;
          cin >> yn ;
          cout << "\n\n";
    }

    system("PAUSE");
    return EXIT_SUCCESS;
}

---

I have one more question, though... It's not that important, but if I enter anything besides 1, it still reruns the program. How could I fix that?

Code:

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while (yn = 1)

---

this is an assignment, not a comparation

comparation is done using ==

Code:

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while (yn == 1)

---

anyway your loop won't work since you tell the program to loop while yn is 1.
Is it correct?

edit:
sorry, I didn't read the code well enough
the real matter is that the loop won't start because, when you run the program, yn is not 1: its value has not been declared.

Using while (yn = 1) worked beacause the statement (yn = 1), which is an assignment, will always result true.

It runs just fine the way it is in my previous post, but it won't exit.

I only made two changes:

I added in a second = to make it a comparison.

and

I set yn = 1 just before the while statement and after the char yn; statement, and it doesn't allow me to rerun the program at all.

I gotta go for now, maybe the day. Thanks for the help so far.

Quote:

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note the separated blocks of lines and where variable declarations should be put

---

IMHO that is more of a personal preference. It is required in C but not C++. Some people recommend declaring variables just before they are used in C++.

you are right cyberfish, I often declare variables not at beginning too.

By the way, in that case these declarations stay well out of the loop ;)

Quote:

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It runs just fine the way it is in my previous post, but it won't exit.

---

Of course, as I told you: it runs fine because while (yn = 1) assigns 1 to yn every loop cycle.
Running the program, even typying in any different number, yn will be changed to 1 again.

Quote:

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I set yn = 1 just before the while statement and after the char yn; statement, and it doesn't allow me to rerun the program at all.

---

You can't rerun the program because you compare (yn == 1) when yn is a char.
A char is interpreted as a character, not a numeric value, so the comparing won't be true when you type in 1.

Two solutions:
1: Declare yn as an int or a bool.

2: Compare yn with a char -> (yn == "r")
and of course change the sentence to "Enter 'r' to rerun program: "

Quote:

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Originally Posted by carlorfeo

2: Compare yn with a char -> (yn == "r")
and of course change the sentence to "Enter 'r' to rerun program: "

---

(yn=='r') actually. Single quotes for char and double quotes are for string.

Thanks abk, you are right.
Of course an assignement follows the same rule: char yn = 'r';
Using double quotes you wil get error: invalid conversion from 'const char*' to 'char'

Quote:

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Originally Posted by carlorfeo

You can't rerun the program because you compare (yn == 1) when yn is a char.
A char is interpreted as a character, not a numeric value, so the comparing won't be true when you type in 1.

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Well, sorry, I really wasn't right saying that!
You can assign a number to a char, but only if you know how to handle it.

e.g.

char ch = 49;
char ch = '1';

these two lines do the same thing, since the ascii code of the character '1' is 49.

Indeed using char's to handle numbers is not a good way
e.g.

char number = 97;
cout << number << endl;

the code above will print a (ascii code = 97)

Thanks for all your help. It's helped a lot. I've got it working perfectly now. It's going to be more than a wind chill calculator. I'll upload it when i'm finished just in case anybody wants to see it. (source code and exe)

Edit:

Here is the source code and exe: http://rapidshare.com/files/90448900/Calc_thingy.zip

I used dev-c++, so the .dev project file is there too.

Quote:

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Originally Posted by willrs2

Thanks for all your help. It's helped a lot. I've got it working perfectly now. It's going to be more than a wind chill calculator. I'll upload it when i'm finished just in case anybody wants to see it. (source code and exe)

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You should actually hide your source code, so other students may not cheat :D

Or I got a better idea - watermark the thing so that if anyone steals it, you know who the culprit is!

True, lol. But I just made the program to learn, it's not a school project. I plan on taking programming next year, though, so thanks for the advice. This is a popular board.