Thread: Small program using "if" and some variables assistance.

Originally Posted by Pielord

Oh, been looking it up and there seem to be numerous different styles involved, any you would recommend or doesn't it really matter as long as I follow something?

Yup.


The last code looks like the easiest thing to implement, but what exactly these lines:

Code:

structureA triangle;
   trig *tri;
 
 
   structureA.hyp;
   structureA.adj;
   structureA.opp;

do, I have no idea.

Anyhow, start off with something easy, and then expand upon it. You could start with the above example, basically having the user input whatever information is necessary for the program to calculate the angle.
Then you could go a little more advanced.

Let me show you an example of how you could make a program to let the user enter all three sides (some being unknown) and all three angles (some being unknown) and allow you to calculate angle or sides.

First off, ask user for all sides and angles. User can input 0 if they are unknown.
Then ask what angle to calculate (name the angles 1, 2 and 3).
From that, determine the opposite side, etc. Then calculate.

A simple example might look like:

Code:

std::array<int, 3> side;
std::array<int, 3> angle;
int angle_to_calc;

std::cout << "Enter sides (0 for unknown): ";
std::cin >> side[0] >> side[1] >> side[2];
std::cout << "Enter angles (0 for unknown): ";
std::cin >> angle[0] >> angle[1] >> angle[2];
std::cout << "Enter angle to calculate: ";
std::cin >> angle_to_calc;

int hypol = side[1], oppol, nearl;
switch (angle_to_calc)
{
    case 1: oppol = side[3]; nearl = side[2]; break;
    case 2: oppol = side[2]; nearl = side[3]; break;
}

float result;
if (hypol != 0 && nearl != 0)
    result = acos((float)nearl / hypol);
else if (hypol != 0 && oppol != 0)
    result = asin((float)oppol / hypol);
else if (nearl != 0 && hypol != 0)
    result = atan((float)oppol / nearl);
else
{
    std::cout << "Insufficient information to calculate angle!\n";
    return 1;
}

std::cout << "The angle is " << result << " radians.\n";

You could make it more complicated, for example, if some needed information is not known, it could try calculating that unknown information. Say you need the hypotenuse. You might calculate that using some other known information. And if some information needed to calculate that is unknown, you could calculate that unknown with some other known information.
That might be a little tricky, but it's certainly possible (especially using recursion).

Everything in the standard library resides in the std namespace. Hence, to access them, I have to tell the compiler what namespace to search in. That's what I do with the "std::". Another alternative is to simply tell the compiler to take everything in the namespace std and dump it in the global namespace. That's what you do with "using namespace std;". The later can cause name collisions (for example, you can't name function min or max because they already exist in the std namespace and because of the importing, now in the global namespace).

hypol, oppol and nearl are all integers (see the declaration).
Only result is a float.

Btw, forgot to attach this picture. The example I showed assumes the triangle looks like this.

Be sure to include <array> and switch on C++11 for your compiler (or get a C++11 compliant compilers, such as GCC or Visual Studio).

Code::Blocks is an IDE, not a compiler, so it is possible.
Go into options and look at the compiler options.

Originally Posted by Elysia

Another alternative is to simply tell the compiler to take everything in the namespace std and dump it in the global namespace. That's what you do with "using namespace std;".

"That" is not what "using namespace std;" does.

The "using namespace std;" directive tells the compiler to treat any names in namespace std as candidates to match names used in code. It does not dump the contents of namespace std into the global namespace. If it did, it not be possible to consistently resolve any naming clash by using the :: operator. For example, "::cout" would always match std::cout, even if there was something else named cout in the global namespace.

It's a compiler option. I strongly suggest you make it work instead of avoiding it since you are missing out on a lot of stuff otherwise.
Perhaps it might help if you mention what compiler you are using. For that matter, GCC works with C::B and has support for C++11.
C++11 might also be known as "C++0x" in some places.

Post your code and error messages. Finally, make sure "C++0x" is enabled when you post your errors.

That's good news. You finally got it working.