Thread: noob here with questions

I need some help with my homework, I've been taking a c++ course for like 7 weeks now and have been running into some problems that the teacher hasn't exactly been covering in class, my first program is just supposed to be a simple switch program, for some reason it's not solving it, I'm sure its something stupid I'm not seeing

Code:

#include <iostream>
using namespace std;

int main()
{
    char opselect;
    double fnum, snum;
    
    cout << "Please type in two numbers ";
    cin  >> fnum >> snum;
    cout << "Please select a code: ";
    cout << "\n     a add";
    cout << "\n     b multiply";
    cout << "\n     c divide";
    cout << "\n";
    cin  >> opselect;

    
    switch (opselect)
    {
           case 'a':
                cout << "The sum of the numbers entered is " << fnum+snum << endl;
                break;
           case 'b':
                cout << "The product of the numbers is " << fnum*snum << endl;
                break;
           case 'c':
                cout << "The dividend of the numbers is" << fnum/snum << endl;
                break;
                
    }

    system("pause");
    return 0;
    
}

also I can't just use int opselect cause we have to use char for some reason, the next thing is a little weirder i guess, we never covered this, we are supposed to put an algorithm into a program, it has 4 steps to convert a numeric value to a certain amount of decimal places, but step three is to get rid of all decimal places, I don't know how I would do that in c++

Code:

 #include <iostream>
using namespace std;

int main()
{
    double money, interest, total;


    cout << "Enter an amount of money: ";
    cin  >> money;
    
    intrest = 0.08675;
    total = money * interest;
    
    total = total * (10*10); // step one
    total = total + 0.5;        // step two
                                         // step three would be to drop all decimal places from total
    total = total / (10*10); // step four finishes it
    
    cout << "The interest is: " << total << endl;
    system("pause");
    return 0;
    
}

I hate to ask these questions but me and my friends cant really figure out how to do it, my teacher wasnt to much help and his response to second program was "just put it directly into the program, thats all i can really tell you" and thanks for any help in advance

For the first program, what's the problem? Is it giving incorrect output? Your use of opselect and the switch seem fine at a quick glance.

For the second program, here's a hint: what's the difference between a double and an int?

my first program is just supposed to be a simple switch program, for some reason it's not solving it

I dont know what "its not solving it" means. I dont see a problem with it (besides the use of "system" and the possibility of runtime error due to dividing by 0).

step three is to get rid of all decimal places, I don't know how I would do that

If you have a double, say "double e = 2.71" and you want to "get rid of the decimal places" the easiest thing to do would be to cast it to a type that doesn't store decimal places. That is, you cast it to an integer by doing something like "(int)". Do a quick search on "casting" to see (and understand!) the full answer.

i didn't exactly get that? keep in mind I've only been doing this for a little over a month now, this is actually my 7th week

edit : also having trouble with the casting, not to sure about that either. I saw like 4 different forms of it, reinterpret, static, const, and dynamic. Am I even looking at the right stuff?

By "drop the decimals" you mean a number like 1.22 should be 1.00? If so, again, just cast it to an integer. Try the following snippet of code in a new "test" c++ program

Code:

double e = 2.17;
// print "e" using cout
e = (int) e;
// print "e" using cout

If you dont know the primitive data types, read a simple article/tutorial explaining them. "int" basically corresponds to the "integer" number. These are "whole" numbers, such as 0, 1, 42, -1234, "float" and "double" loosely corresponds to "real" numbers. These are (practically*) "all other numbers", such as 0, 1, 1.0, 1.1111, -42, -1234.5678. The set of integers is a subset of the real numbers, as you can see here, all "int"s can be considered as a "double". However, if you consider a "double" as an "int", you will be loosing the fractional part (part to the right of the decimal), and this will likely cause a warning or error by your compiler because its saying "Oops! You might be loosing information/precision about this number, I'll prevent that from happening." If you "cast" it to an integer then the compiler will let you "throw away" the fractional part.


* Math people: I'm aware of imaginary numbers, but for the sake of simplicity I've excluded it in the discussion above... so you don't need to correct me.

>> Reading a char does not skip the leading newline.
I don't think that's correct, hk_mp5kpdw. The operator>> will skip the preceding newline even if it is reading in a char.

The code for the first program works or me. What exact input are you giving it, rllove37?

Hazaa I got the money one to work just did this

Code:

 total = total * (10*10);
    total = total + 0.5;
    total = (int) total;
    total = total / (10*10);

thanks on that one, but I am still not sure why the first one isn't working

>> I am still not sure why the first one isn't working
It works for me. Are you sure you built your changes and are using the latest version?

Originally Posted by rllove37

Hazaa I got the money one to work just did this

Code:

 total = total * (10*10);
    total = total + 0.5;
    total = (int) total;
    total = total / (10*10);

thanks on that one, but I am still not sure why the first one isn't working

I'd strongly recommend you understand why it works, before moving on and feeling proud . Seriously.

As for the first one, Im not sure what you mean in your explanation of how you entered the numbers. Does the flow of the input/output look similar to this?

Code:

jordan@jordan-laptop:~$ ./yourprogram 
Please type in two numbers 1 2
Please select a code: 
     a add
     b multiply
     c divide
a
The sum of the numbers entered is 3

Where red text indicates input.

Originally Posted by nadroj

I'd strongly recommend you understand why it works, before moving on and feeling proud . Seriously.

i understand it, intergers have no decimal places, i just didn't know you could change it in the middle of a program like that.

On the other program, apparently I still had opselct as an int... (facepalm) my bad

edit: btw thanks guys