Calculate two numbers in three ways

[yabubata]

Hello guys!
I´m trying to write a program in where the user digit two numbers, and chooses either addition, multiplication or square-sum of these two numbers. The functions seems to work fine until the actual calculations. I´m a totally noob, so maybe I´m doing it all wrong... Hope anyone can explain what´s wrong.
Thank you!
//Fredrik

  #include <iostream>
#include <cmath>
using namespace std;

// Function declaration

void skrivInfo();
void lasEttTal (int &tal1, int &tal2);
char lasOp();
void ordna (int &tal1, int &tal2);
int berakna (int tal1, int tal2, char op);
void skrivResultat (int summa);

// Main program

int main()
{
    int tal1, tal2, summa;
    char op;
    skrivInfo();
    lasEttTal (tal1, tal2);
    op = lasOp();
    ordna (tal1, tal2);
    summa = berakna (tal1, tal2, op);
    skrivResultat(summa);
    return 0;
}

// Func. def.
// Hello

void skrivInfo()
{
    cout<<"Hej det här programmet räknar addition, multiplikation eller kvadratsumman av två tal."<<endl;
}

//Func. lasEttTal that lets the user to write two numbers

void lasEttTal (int &tal1, int &tal2)
{
    cout<<"Skriv in två heltal: ";
    cin>>tal1>>tal2;
}

//Funk. lasOp that lets the user to choose which operation

char lasOp()
{
    char op;
    char t1='a';
    char t2='m';
    char t3='k';
    
    cout<<"Välj vilken beräkning som skall göras: "<<t1<<" addera, "<<t2<<" multiplicera, eller "<<t3<<" kvadratsumman av två tal: ";
    cin>>op;
    
    while (!((op==t1)||(op==t2)||(op==t3))) //if none of these (wrog choice)
    {
        cout<<"Fel inmatning"<<endl;
        cout<<"Välj vilken beräkning som skall göras "<<t1<<" addera, "<<t2<<" multiplicera, eller "<<t3<<" kvadratsumman av tal";
        cin>>op;
    }
    
    return op;
    };

//Func. to make them in order of magnitude
    
void ordna (int &tal1, int &tal2)
    
    {
        if(tal1>tal2)
        {
            int temp = tal1;
            tal1=tal2;
            tal2=temp;
        }
    }
    
// Func. to calculate according to choises in LasEttTal and in lasOp
    int berakna (int tal1, int tal2, char op)
    {
        int summa=0; //nollställa
        cout<<tal1<<endl;
        cout<<tal2<<endl;
        cout<<op<<endl;
        
        if(op=='a')
        {
            for(int tal1; tal1<=tal2; tal1++)
            {
                summa +=tal1; //addition
                cin>>summa;
                cout<<summa<<endl;
            }
        }
        
        if(op=='m')
        {
            for(int tal1; tal1<=tal2; tal1++)
                summa*=tal1; //multiplication
                cin>>summa;
                cout<<summa<<endl;
        }
        if(op=='k')
        {
            for(int tal1; tal1<=tal2; tal1++);
            summa=tal1*tal1 + tal2*tal2; // Square-sum
            cin>>summa;
            cout<<summa<<endl;
        }
        
        
          return summa;
        
}
// Func. write the result

void skrivResultat(int summa)
{
    
    cout<<"Resultatet av beräkningen är: "<<summa<<endl;
}

[48T7M4Gy]

if(op=='k')
        {
            for(int tal1; tal1<=tal2; tal1++); // <--- ?? does nothing
            summa=tal1*tal1 + tal2*tal2; // Square-sum
            cin>>summa;   // <----- this is wrong?**
            cout<<summa<<endl;
        }

** this is just an example of a possible error.

Here you are calculating summa, then getting a new value via cin, then cout'ing the new value.

This doesn't make sense because why would you calculate the first summa and not use it?

[48T7M4Gy]

PS I just noticed you do the same with each operation.

Also the for loop is doing nothing and besides it has a syntax problem. I suggest you comment ot that line.

should be:

if (op == ...)
{
   summa = ... ;
   cout << summa etc << endl;
}

[48T7M4Gy]

// Func. to calculate according to choises in LasEttTal and in lasOp

int berakna (int tal1, int tal2, char op)
    {
        int summa=0; //nollställa
        cout<<tal1<<endl;
        cout<<tal2<<endl;
        cout<<op<<endl;
        
        if(op=='a')
           summa = tal1 + tal2; //addition

        if(op=='m')
           summa = tal1 * tal2; //multiplication

        if(op=='k')
           summa=tal1*tal1 + tal2*tal2; // Square-sum

          cout << summa;
          return summa;
}

or, you can have:

int berakna (int tal1, int tal2, char op)
    {
        cout<<tal1<<endl;
        cout<<tal2<<endl;
        cout<<op<<endl;
        
        if(op=='a')
           return tal1 + tal2; //addition

        if(op=='m')
           return tal1 * tal2; //multiplication

        if(op=='k')
           return tal1*tal1 + tal2*tal2; // Square-sum

          cout << "Error";
          return 0;
}

[48T7M4Gy]

also in main()

cout << berakna (3, 4, 'k') << endl;

or

int xyz = berakna (3, 4, 'k');
cout << xyz << endl;

Should display 25 in each case. E&OE

[yabubata]

Thanks Kemort! Logically, "cin" is wrong, and I erased it on all three (I don´t know why I but it there. The reason for "for"-loop is that I want lowest number and the highest number, but also the numbers in between (integer): 5 and 7: Addition > 5+6+7=18. I´m doing it wrong in some way...
Yours
Fredrik

[48T7M4Gy]

OK
a for loop looks like this, I suggest you try it yourself.

Say you want to print out all the numbers from 1 to 6, and get their total

int summa = 0;
for ( int i = 1; i <= 6; i++ )
{
    summa += i;
    cout << i << ' ' << summa << endl;
}

cout << "Summa:  

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

[yabubata]

I´ll try that. Thanks!!