C++ Homework?? (Area of a Shaded Region)

[Ben Conover]

I gotta make a c++ program that calculates the area of a shaded region when the user types in the radius.
The picture is square with a circle tightly circumscribed within it so each quadrant is touching a midpoint. And the shaded region is between the 2 shapes.

CODE:

#include <iostream>
// variables
double pi = 3.14159;
double circlearea = 0;
double squarearea = 0;
double result = 0;
double radius = 0; //to be obtained by user

int main ()
{
std::cout << "Enter a Radius";
std::cin >> radius;
if (radius < 0)
{

std::cout << "Negative number!";
return 0;
//end if radius <0

circlearea = (pi * radius * radius);
std::cout << "The area of the circle is:" << circlearea <<std::endl;
squarearea = (2 * radius * 2 * radius);
std::cout << "The area of the square is:" << squarearea <<std::endl;
result = (squarearea - circlearea);
std::cout << "The area of the shaded region is:" << result <<std::endl;
}
}

[TheMeerkat]

Use code tags and point out what lines 22, 24 and 26 are.

To use code tags, put your code between these: [code][/code]

[Ben Conover]

there. now what did I do wrong? This is due tomorrow night. :/

[TheMeerkat]

you don't have ';' at the end of lines 21, 23 and 25. Also you use 'Radius' and 'radius'.

Also you didn't actually do use your code tags correctly. There is a button to the right of the the box that you reply in that looks like <> click that and the tags should come

It should look like this:

#include <iostream>
// variables
double pi = 3.14159;
double circlearea = 0;
double squarearea = 0;
double result = 0;
double radius = 0; //to be obtained by user

int main ()
{
std::cout << "Enter a Radius";
std::cin >> radius;
if (radius < 0)
{

std::cout << "Negative number!";
return 0;
//end if radius <0

circlearea = pi * radius * radius;
std::cout << "The area of the circle is:" << circlearea <std::endl;
squarearea = 2 * radius * 2 * radius;
std::cout << "The area of the square is:" << squarearea <std::endl;
result = squarearea - circlearea;
std::cout << "The area of the shaded region is:" << result <std::endl;
}

[Ben Conover]

That gets some of that out of the way now i still got:


Area2.cpp:21: no match for `ostream & < ostream & ()(ostream &)'
Area2.cpp:21: candidates are: operator <(ostream & (*)(ostream &), ostream & (*)(ostream &)) <builtin>
Area2.cpp:21: operator <(void *, void *) <builtin>
Area2.cpp:23: no match for `ostream & < ostream & ()(ostream &)'
Area2.cpp:23: candidates are: operator <(ostream & (*)(ostream &), ostream & (*)(ostream &)) <builtin>
Area2.cpp:23: operator <(void *, void *) <builtin>
Area2.cpp:25: no match for `ostream & < ostream & ()(ostream &)'
Area2.cpp:25: candidates are: operator <(ostream & (*)(ostream &), ostream & (*)(ostream &)) <builtin>
Area2.cpp:25: operator <(void *, void *) <builtin>
Area2.cpp:27: parse error at end of input

[TheMeerkat]

Maybe try putting the calculations part in brackets. Not sure why that should matter, but it wouldn't be the first time putting things in brackets solved a problem like this.

Something like this:
squarearea = (2 * radius * 2 * radius);

[Ben Conover]

nothing changed

[TheMeerkat]

Hmm... I can't really see if it seems to do circlearea ok why it's not doing squarearea. I take it it is printing out what you expect it to for circlearea?

[Ben Conover]

The errors are for the 3 cout lines and the end

[malice]

Could it be that you have <std::endl; instead of << std::endl;?

[TheMeerkat]

Haha, yea can't believe I didn't notice that. Although the space I don't think should matter, but << instead of < obviously does.

[Ben Conover]

yep. now it's just the "parse error at end of input" in line 27

[malice]

You're missing a curly bracket, the one you have there closes the if statement, not main().

[shacktar]

I think your if statement is missing a }

[Ben Conover]

Now it runs.
It does:

Hit any key to start. Hit key
Enter a Radius Type number
Hit any key to continue Hit key

Exits

[shacktar]

We'll have to see the new code with [code][/code] tags, please.

[Ben Conover]

updated the 1st post

[shacktar]

You're ending the if statement in the wrong place. The area calculations are within the if (radius < 0) statement, not to mention they won't get hit because the program returns before then. You should close the if statement here:

return 0;
//end if radius <0   <--- brace goes here 

[Ben Conover]

ok. i put a brace in line 19 and get
Area2.cpp:27: parse error before `}'

[shacktar]

Now you have too many braces. Remove one of the last ones.