Returning a specific value

[sidthekid2014]

How do I return a specific value from a function in order for me to cout it in my int main?

In this case i have solved for a value sigma1 in my function but i want to use the value of sigma1 in my int main also and in other places so how would i do that?

#include <iostream>
#include <cmath>
#include <iomanip>
#include <cstdlib>

using namespace std;

bool isInt (double value) {
    double dummy;
    return bool(modf(value, &dummy) == 0);
}

double sqr(double value) { 
	return value * value; 
}

double computeSolidity(double B1,double B2);


int main (void) {
    double B1;
    double B2;
    double I;
    double conditionB1;
    double alpha1;
    
for (;;){
     cout << "Enter Flow Entry Angle , Flow Exit Angle , and Incidence (-1 -1 -1 to exit) " << endl;
     cout << endl;
     cin >> B1 >> B2 >> I;
     cout << endl;
    if ( B1 == -1 && B2 == -1 && I == -1){
        
        break;
        }else{
            conditionB1 = (36-(0.45*B2))/(B1-B2); 
        if(B2 <= -10 || B2 >= 50 || I <= -3 || I >=3 || conditionB1 >= 1.25 || conditionB1 <= 0.75  ){
            cout << "Error ! Invalid Values Ignored " << endl; 
            }else{
                alpha1 = B1 - I;
        computeSolidity(B1,B2);
        cout << endl;
        
            cout << "Blade Entry Angle : " << alpha1 << endl;
            cout << "Solidity : " << sigma1 << endl; // how to get sigma 1?? 
            } 
    
    }
    
    
    
}   


    system("PAUSE"); return 0;

}

double computeSolidity(double B1,double B2){
    
    double LHS;
    double sigma = 0.6;
    double sigma1;
    double LHScount;
double LHScount1;  
    
     cout << "Solidity" << setw(20) << "LHS(Value)" << endl;
    cout <<"------------------------------" << endl ;
    for(sigma; sigma<2.2 ;sigma+=0.1){
    LHS = 33.5291 + (0.469188 + 0.0020961*B2)*B2 - B1 + (0.187148*B2-15.2599)*log(1/sigma)-0.677212*(pow(log(1/sigma),2));
           if(sigma==0.6){
                LHScount1 = abs(LHS);
                }else{
                    LHScount = abs(LHS);
                    if( LHScount < LHScount1){
                        LHScount1 = LHScount;
                        sigma1=sigma;
                        
                        }
                    
                    }
           
        cout << setiosflags (ios::showpoint|ios::fixed);
        
cout <<setw(5) << setprecision(1)<< sigma << setw(20) << setprecision(4) <<LHS << endl;

}
cout << "Leaving Function The chosen value is " << setprecision(1) << sigma1 << endl;

return sigma1;

}

[Peter87]

If you want to use the return value of a function later on you will have to store it in a variable.

double sigma1 = computeSolidity(B1,B2);

Note that this variable is a different variable than sigma1 inside the computeSolidity function so you don't have to use the same name if you don't want to.

[sidthekid2014]

Where would I declare it though plus i dont think my function is returning sigma1 for some odd reason it doesnt return anything

[sidthekid2014]

Same problem the program crashes when i declare

double sigma1 = computeSolidity(B1,B2)

in the Int main function

[Chervil]

That doesn't sound like the same problem. There's a big difference between a function failing to return a value, and the entire program crashing.

[sidthekid2014]

Ok i have fixed the issue i was computing the function twice and thats why the program was crashing thanks alot for your help guys :) appreciate it