Switch Statements; CASES BEGIN WITH SAME LETTER?

[elevona]

Hi! In this program, I am using switch statements in order to execute commands from a made up language. However, I cannot seem to get my program to distinguish DOUBLE from DIV, as you can only use one character to discriminate between cases. I would like to use an If or If/else statement to distinguish DOUBLE from DIV. I cannot use "Hello[1]" or however you would put it. Would I make an empty variable? What goes in the if ( ) ? Help? Thanks so much!

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

int main()
{

	char userInput;
	int userAdd, userAdd1, userAnswer;
	string userCON1, userCON2;

	cout << "Please enter the operation: \n";
	cin >> userInput;
	
	switch (userInput)
	{
	case 'A' :
		cout << "You are using the ADD function.\n";
		cin.ignore(200, '\n');
		cout << "Please enter an integer.\n";
		cin >> userAdd;
		cout << "Thanks. Please enter the second integer.\n";
		cin >> userAdd1;
		userAnswer = userAdd + userAdd1;
		cout << "The answer is: " << userAnswer;
		break;

	case 'C' : 
		cout << "You are using the COMBINE function.\n";
		cin.ignore(200, '\n');
		cout << "Please enter a string.\n";
		getline(cin, userCON1);
		cout << userCON1;
		break;

	case 'D' : 
///?
if ( ) 
    cout >> "You are using the DOUBLE function";
else
cout >> "You are using the DIV function";
		
//?
		
	}





	return 0;

[salem c]

So you can't do this?

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

int main() {
    string userInput;
    getline(cin,userInput);
    switch(userInput[0]) {
        case 'D':
        {
            switch(userInput[1]) {  // Or your if () approach
                case 'I':   // DIV
                    break;
                case 'O':   // DOUBLE
            }
        }
    }
    return 0;
}

Plus, by using getline to begin with, you can drop all those cin.ignore lines you have.

[elevona]

That is correct. I cannot use that specifically, but I can put switches in switches or ifs in switches. I just am a little stuck on this part. Thank you for the help thus far. Do you know if there is a way to do that?

[elevona]

Also note that my userInput is a character; this is how it must be! Thanks again

[Duthomhas]

There was recently another thread about using strings in a switch.
^{_{http://www.cplusplus.com/forum/general/251347/}}

For what you are doing, there really are only two good ways:

(1) Use if..else if chains.

  if (userInput == "ADD")
  {
    ...
  }
  else if (userInput == "COMBINE")
  {
    ...
  }
  else if (userInput == "DIVIDE")
  {
    ...
  }
  else if (userInput == "DOUBLE")
  {
    ...
  }

(2) Use a lookup and dispatch. A simple std::map makes this extra easy:

void f_add();
void f_combine();
void f_divide();
void f_double();

  std::map <std::string, void(*)()> dispatch
  {
    { "ADD",     f_add },
    { "COMBINE", f_combine },
    { "DIVIDE",  f_divide },
    { "DOUBLE",  f_double },
  };
  if (dispatch.count( userInput )) dispatch[userInput]();

Hope this helps.

[elevona]

I think that both pieces of advice are very helpful, but I cannot change the format of the current code that I am providing. I must do this inside of a switch statement and preferably with an embedded 'if' statement. Thank you for the advice, though. I will save it for later purposes.

[salem c]

*shrug*
If you really want a complete hands tied behind your back answer, then perhaps.

	cout << "Please enter the operation: \n";
	cin >> userInput;
	
	switch (userInput)
	{
	case 'A' :
		cout << "You are using the ADD function.\n";
		cin.ignore(200, '\n');
		cout << "Please enter an integer.\n";
		cin >> userAdd;
		cout << "Thanks. Please enter the second integer.\n";
		cin >> userAdd1;
		userAnswer = userAdd + userAdd1;
		cout << "The answer is: " << userAnswer;
		break;

	case 'C' : 
		cout << "You are using the COMBINE function.\n";
		cin.ignore(200, '\n');
		cout << "Please enter a string.\n";
		getline(cin, userCON1);
		cout << userCON1;
		break;

	case 'D' : 
		cin >> userInput;  // Get another letter
		///?
		if ( userInput == 'O' ) 
			cout >> "You are using the DOUBLE function";
		else
			cout >> "You are using the DIV function";
		
//? 

[elevona]

Hey!

Grabbing another character worked! Thanks so much!

[Duthomhas]

Ah, I take it this is a homework assignment.

Sometimes I wonder what a student is supposed to get from unimaginative assignments poorly fitting to the learning objective(s)...

[salem c]

Quite.

If this were a course in teaching people to run marathons, the initial objective seems to be to create a level playing field by breaking the legs of all the students.
Then teaching them how to crawl, hobble, walk and finally run at some reduced speed.