switch_case_not_working :S

**pico** · 03-04-2005

hi, i want to make a calculator. ive done it before but now after some years i come back to c++ and it doesnt work

here my code

Code:

#include <iostream.h>

int main()
{
	char option[1];
	cout<<"Welcome to PicoCalc ;0)"<<'\n';
	cout<<"Choose your function: +,-,* or /"<<'\n';

	cin>>option;
	switch(option);
	{
	case '+':
		cout<<"Enter first number:"<<'\n';
		int num1;
		cin>>num1;
		cout<<"Enter second number:"<<'\n';
		int num2;
		cout<<"Result is "<<num1+num2<<'\n';
		break;
	case '-':
		cout<<"Enter first number:"<<'\n';
		int num1;
		cin>>num1;
		cout<<"Enter second number:"<<'\n';
		int num2;
		cout<<"Result is "<<num1-num2<<'\n';
		break;
	case '*':
		cout<<"Enter first number:"<<'\n';
		int num1;
		cin>>num1;
		cout<<"Enter second number:"<<'\n';
		int num2;
		cout<<"Result is "<<num1*num2<<'\n';
		break;
	case '/':
		cout<<"Enter first number:"<<'\n';
		int num1;
		cin>>num1;
		cout<<"Enter second number:"<<'\n';
		int num2;
		cout<<"Result is "<<num1/num2<<'\n';
		break;
	default:
		cout<<"Invalid choise!"<<'\n';
	}

	cout<<"test";			//here i will put option to make another calculation..

	return (0);
}

i compile using visual c++ and get following errors:

Code:

C:\Documents and Settings\user\Desktop\example4\example4.cpp(14) : error C2450: switch expression of type 'char [1]' is illegal
        Integral expression required
C:\Documents and Settings\user\Desktop\example4\example4.cpp(14) : warning C4060: switch statement contains no 'case' or 'default' labels
C:\Documents and Settings\user\Desktop\example4\example4.cpp(16) : error C2046: illegal case
C:\Documents and Settings\user\Desktop\example4\example4.cpp(23) : error C2043: illegal break
C:\Documents and Settings\user\Desktop\example4\example4.cpp(24) : error C2046: illegal case
C:\Documents and Settings\user\Desktop\example4\example4.cpp(26) : error C2086: 'num1' : redefinition
C:\Documents and Settings\user\Desktop\example4\example4.cpp(29) : error C2086: 'num2' : redefinition
C:\Documents and Settings\user\Desktop\example4\example4.cpp(31) : error C2043: illegal break
C:\Documents and Settings\user\Desktop\example4\example4.cpp(32) : error C2046: illegal case
C:\Documents and Settings\user\Desktop\example4\example4.cpp(34) : error C2086: 'num1' : redefinition
C:\Documents and Settings\user\Desktop\example4\example4.cpp(37) : error C2086: 'num2' : redefinition
C:\Documents and Settings\user\Desktop\example4\example4.cpp(39) : error C2043: illegal break
C:\Documents and Settings\user\Desktop\example4\example4.cpp(40) : error C2046: illegal case
C:\Documents and Settings\user\Desktop\example4\example4.cpp(42) : error C2086: 'num1' : redefinition
C:\Documents and Settings\user\Desktop\example4\example4.cpp(45) : error C2086: 'num2' : redefinition
C:\Documents and Settings\user\Desktop\example4\example4.cpp(47) : error C2043: illegal break
C:\Documents and Settings\user\Desktop\example4\example4.cpp(48) : error C2047: illegal default
Error executing cl.exe.

example4.exe - 16 error(s), 1 warning(s)

any ideas?
cheers

**Brain Cell** · 03-04-2005

ok , lets start cleaning up this mess :

Code:

#include <iostream.h>

Although its not an error , but you're following the old C++ standard. The new way to do this is either :

Code:

#include <iostream>
using namespace std;

or better :

Code:

#include <iostream>
using std::cout;
using std::cin;

The second option is recommended to avoid naming conflicts , not a biggie though.

Code:

char option[1];

If you're going to store one character only , then why didn't you just declare a regular character instead of a one-character-array?

This messed up the switch statement because 'option' has the memory adress of the first element of your array , whereas 'option[0]' has the first value (remember when referring to elements you start counting from 0).

Your switch statement took a memory adress instead of a value , therefore none of the cases matched it. But wait !! did the switch statement even work? no. Becuase you terminated it right away with a semi-colon here :

Code:

switch(option);
	{

if you remove that semi-colon you'll get rid of some of the errors. If you still insist on using s single character array though , just replace the input with 'cin >> option[0];' and use 'option[0]' within the switch statement.

This error :

'num1' : redefinition

showed up because you defined 'num1' more than once. You should've defined num1 and num2 before the switch statement then use them within the cases.

another error here :

Code:

cout<<"Enter second number:"<<'\n';
		int num2;

Seems like you typed 'int' instead of 'cin >>' by mistake. But you repeated that with the rest of the cases.

fix those errors and your program should work again.

Here's a big hint : read what the error(s) say

**pico** · 03-04-2005

hi thx ur reply mate.
i read wat the errors said, but just "illegal case/break" etc didnt give me any tip. obviously there was a problem with the switch statement, i'll remove the colon and it should be fine

**okinrus** · 03-04-2005

You're defining variables inside the case statement. You can't in general do that.
For instance, if you have

Code:

switch(a) {
case 5:
     int c;
case 6:
     int d;
     c = 5;
}

Whether c = 5 in case 6 makes "sense" is whether case 5 dropped into case 6. But C++ determines scope statically. If you really need to define variables within the cases, you can do

Code:

switch(a) {
case 4: 
{
      int c;
}

}

But this, looks ugly. Your're better off either defining the variables outside of the switch statement or creating a new function.

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