Creating options and menus

raptorhawk · #1 03-May-2005, 13:25

I'm trying to create a program that will, when you launch it, ask you if you either want to convert the temperature from Fahrenheit to Celsius or Celsius to Fahrenheit. I think im on the right track but the program closes when I put in the temperatrue. For some reason it doesnt get the the part of the code that shows the result.

CPP / C++ / C Code:

#include <iostream>


float Convert(float);
float Change(float);

  using namespace std;

  float TempFer;
  float TempCel;
  int choice;

  int main()
{
  cout << "Please select: \n";
          cout << "(1) Fahrenheit to Celsius.\n";
          cout << "(2) Celsius to Fahrenheit.\n";
          cin >> choice;

          if (choice == 1)
                        {cout << "Please enter the temperature in Fahrenheit: ";
                        cin >> TempFer;
						{TempCel = Convert(TempFer);}
                        cout << "\nHere's the temperature in Celsius: ";
                        cout << TempCel << endl;
						return 0;}

          if (choice == 2)
                        {cout << "Please enter the temperature in Celsius: ";
                        cin >> TempCel;
						{TempFer = Convert(TempCel);}
                        cout << "\nHere's the temperature in Fahrenheit: ";
                        cout << TempFer << endl;
						return 0;}

                else
				{cout << "Sorry, you entered an invalid number.";
				return 0;}
}


float Change(float TempFer)
{
  float TempCel;
  TempCel = ((TempFer - 32) * 5) / 9;
  return TempCel;
}


float Convert(float TempCel)
{
  float TempFer;
  TempFer = (TempCel * 9 / 5) + 32;
  return TempFer;
}

nkhambal · #2 03-May-2005, 13:56

why these lines are in braces? Did you try removing the braces arround them and check?

CPP / C++ / C Code:

{TempCel = Convert(TempFer);}
{TempFer = Convert(TempCel);}

Also, use following structure for if loop

CPP / C++ / C Code:

if (choice == 1)
{
   /* Do something */
} else if (choice == 2)
{
    /* Do something */
} else {
    printf("Invalid choice..Bye\n");
}

return 0;

Or better yet, use "switch"

CPP / C++ / C Code:

switch (choice)
{
   1: /* Do something */ break;
   2:  /* Do something */ break;
   default:  printf("Invalid choice..Bye\n"); break;
}

return 0;

ubergeek · #3 03-May-2005, 19:27

Quote:

or better yet, use "switch:"
...

yikes! can't be giving incorrect code as examples!
correct switch structure is:

CPP / C++ / C Code:

switch (choice)
{
case 1: //note the "case"
//choice == 1
break;
case 2:
//choice == 2
break;
default:
//choice != 1 && choice != 2
break;
}

also, a common headache with switches is that you declare a variable inside one of the cases, and then you get an error like "jump to case label bypasses declaration of ..." or something similar. The reason for this has something to do with scope that is not important. What is important is that when you declare a variable inside a switch, put brackets around that case. Code says thousand words:

CPP / C++ / C Code:

switch (choice)
{
case 1:
    { //need these
        int Fahren;
    } //without the braces, you will get an error
    break; //you still need a break statement. It can go inside or outside of the braces.
case 2:
//choice is 2
break;
default:
    {
        //choice is neither 1 nor 2
        bool failed = true;
    }
break;
}

nkhambal · #4 03-May-2005, 19:45

sorry...

WaltP · #5 03-May-2005, 22:31

Please read the tutorial on formatting. Bad formatting is sometimes worse than no formatting.

And forget switch. The if works just fine for now. Output your values as soon as you enter them to make sure they are being read properly.

raptorhawk · #6 04-May-2005, 13:11

Ok, I reformated the code and added a line to read back the input choice but my origional problem still remains. Why is the program ending before it reads back the conversion? Here is the code.

CPP / C++ / C Code:

#include <iostream>


float Convert(float);
float Change(float);

using namespace std;

float TempFer;
float TempCel;
int choice;

int main()
{
  cout << "Please select: \n";  // Gives you the option.
  cout << "(1) Fahrenheit to Celsius.\n"; // 1 or
  cout << "(2) Celsius to Fahrenheit.\n"; // 2
  cin >> choice;
  cout << "Your choice was " << choice << "\n";  // Read back the choice

    if (choice == 1)  // Fahrenheit to Celsius
     {cout << "Please enter the temperature in Fahrenheit: ";
     cin >> TempFer;
	 TempCel = Convert(TempFer);
     cout << "\nHere's the temperature in Celsius: ";
     cout << TempCel << endl;
	 return 0;}

     if (choice == 2) // Celsius to Fahrenheit
     {cout << "Please enter the temperature in Celsius: ";
     cin >> TempCel;
	 TempFer = Convert(TempCel);
     cout << "\nHere's the temperature in Fahrenheit: ";
     cout << TempFer << endl;
	 return 0;}

     else  // Wrong number
     {cout << "Sorry, you entered an invalid number.";
	 return 0;}
}


float Change(float TempFer)  // Actual conversion to Celsius
{
  float TempCel;
  TempCel = ((TempFer - 32) * 5) / 9;
  return TempCel;
}


float Convert(float TempCel)  // Actual conversion to Fahrenheit
{
  float TempFer;
  TempFer = (TempCel * 9 / 5) + 32;
  return TempFer;
}

Dave Sinkula · #7 04-May-2005, 13:27

Window closes?

nkhambal · #8 04-May-2005, 13:34

For F to C conversion you are calling function Convert() same as for C to F.

Shouldn't you be calling Change() for F to C ?

I tried it on my machine, it seems to be working fine.

Quote:

$ ./temp.exe
Please select:
(1) Fahrenheit to Celsius.
(2) Celsius to Fahrenheit.
1
Your choice was 1
Please enter the temperature in Fahrenheit: 68

Here's the temperature in Celsius: 20

KenshuuSei · #9 04-May-2005, 19:52

Just a suggestion, its better to have a single return in main or any function..

CPP / C++ / C Code:

int main()
{
  cout  << "Please select: \n";              // Gives you the option.
        << "(1) Fahrenheit to Celsius.\n";   // 1 or
        << "(2) Celsius to Fahrenheit.\n";   // 2

  cin   >> choice;

  cout  << "Your choice was "                // Read back the choice
        << choice
        << endl;

  if (choice == 1)                           // Fahrenheit to Celsius
  {
    cout  << "Please enter the temperature in Fahrenheit: ";
    cin   >> TempFer;

    TempCel = Change(TempFer);

    cout  << "\nHere's the temperature in Celsius: ";
          << TempCel
          << endl;
  }

  else if (choice == 2)                      // Celsius to Fahrenheit
  {
    cout  << "Please enter the temperature in Celsius: ";
    cin   >> TempCel;

    TempFer = Convert(TempCel);

    cout  << "\nHere's the temperature in Fahrenheit: ";
          << TempFer
          << endl;
  }

  else                                       // Wrong number
  {
    cout  << "Sorry, you entered an invalid number."
          << endl;
  }

  return 0;
}

raptorhawk · #10 06-May-2005, 13:28

where do I put cin.get?

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