CODEWITHSUNDEEP
c++functionstructpass-by-reference
cppstudent1
cppstudent1

Reputation: 11

C++ functions within struct and calling values by reference

All- I've researched this quite a bit. My program compiles without error, but the values from the functions within the struct are not passing to the program. Can you help me to figure out why they are not? I included the snippets of code that show the components in question. Mainly, my code like: "&allData::ConvertToC" is not returning any value from the function within the struct "allData". It only will return a value of 1, no matter the input of "allData.temperature". I know the all components of the program, other than those mentioned are working.

code snippets:

//defining the struct

struct allData {
    char selection; 
    double centigrade; 
    double fahrenheit; 
    double temperature; 
    double ConvertToC (const double& temperature);
    double ConvertToF (const double& temperature);
} allData;

//adding data to the struct for the functions within the struct to use

cout << "Enter C for converting your temperature to Celsius, or enter F for converting your temperature to Fahrenheit, and press ENTER." << endl << endl;

cin >> allData.selection; 

cout << "Enter your starting temperature to two decimal places, and press ENTER." << endl << endl; 

cin >> allData.temperature; 

switch (allData.selection) {

//my attempt to reference the functions within the struct and the data in the struct, but it is not working and always returns a value of 1. 

case 'c': { &allData::ConvertToC; 

    cout << "Your temperature converted to Celsius is: " << &allData::ConvertToC   
    << endl << endl; 
    break; 
    }

case 'C': { &allData::ConvertToC; 

    cout << "Your temperature converted to Celsius is: " << &allData::ConvertToC    
    << endl << endl; 
    }
}


//Function definitions that are located in the struct. Do I define the functions in the normal way, like this, if they are located in the struct?

double allData::ConvertToF (const double& temperature) {

    double fahrenheit = 0;
    fahrenheit = temperature * 9 / 5 + 32;
    return fahrenheit; 

}


double allData::ConvertToC (const double& temperature) {

    double centigrade = 0;
    centigrade = (temperature - 32) * 5 /9; 
    return centigrade; 

}

Upvotes: 0

Views: 144

Answers (2)

schenken
schenken

Reputation: 46

// Name of struct made distinct from its instance, for clarity.
struct AllData {
    char selection;
    double centigrade;
    double fahrenheit;
    double temperature;
    double ConvertToC ();
    double ConvertToF ();
} allData;

...

allData.selection = 'C';
allData.temperature = 74.5;

switch (allData.selection)
{
case 'c':
case 'C':
    cout << "Your temperature converted to Celsius is: " << allData.ConvertToC() << endl << endl;
    break;
}

...

double AllData::ConvertToF ()
{
    //double fahrenheit = 0;    Why not store the result in the struct?
    fahrenheit = temperature * 9 / 5 + 32;
    return fahrenheit;
}

double AllData::ConvertToC ()
{
    //double centigrade = 0;
    centigrade = (temperature - 32) * 5 / 9;
    return centigrade;
}

Upvotes: 0

Fallso
Fallso

Reputation: 1301

You're not executing the function call, you're just passing a function pointer to the cout stream.

I think what you really want is something like:

 cout << "Your temperature converted to Celsius is: " << allData.ConvertToC(allData.temperature) << endl;

In addition you don't need to pass by reference in the "ConvertToC" method as you're not really saving anything (a "double" is 8 bytes wide, and references/pointers are 4 bytes on 32 bit systems, or 8 bytes on 64 bit systems).

Upvotes: 1

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