Looping with enum

Spidy08 · #1 01-Oct-2007, 17:50

CPP / C++ / C Code:

enum myenum{a,b,c,d,e};

void test(myenum temp)
{
   ...
}

void main()
{
   //how do I use a loop to call test and send it each enum value?
}

davekw7x · #2 01-Oct-2007, 21:57

Quote:

Originally Posted by Spidy08

CPP / C++ / C Code:

enum myenum{a,b,c,d,e};
... loop to c...send it each enum value?
}

CPP / C++ / C Code:

#include <iostream>

using namespace std;

enum myenum{a,b,c,d,e};

void test(enum myenum temp)
{
    printf("   In test: ");
    switch (temp)
    {
        case a: cout << "temp == a" << endl;
                break;

        case b: cout << "temp == b" << endl;
                break;

        case c: cout << "temp == c" << endl;
                break;

        case d: cout << "temp == d" << endl;
                break;

        case e: cout << "temp == e" << endl;
                break;

        default: cout << "Grievous program error, argument to test == "
                 << temp
                 << endl;
    }
    cout << endl;
}


int main()
{
    myenum i;
    for (i = a; i <= e; i = myenum(i+1)) {
        cout << "In main(): calling test(" << i << ")" << endl;
        test(i);
    }
    cout << endl;
    cout << "After loop: calling test(" << i << ")" << endl;
    test(i);
    return 0;
}

Output:

Code:

In main(): calling test(0)
   In test: temp == a

In main(): calling test(1)
   In test: temp == b

In main(): calling test(2)
   In test: temp == c

In main(): calling test(3)
   In test: temp == d

In main(): calling test(4)
   In test: temp == e


After loop: calling test(5)
   In test: Grievous program error, argument to test == 5

Regards,

Dave

ahbi82 · #3 01-Oct-2007, 23:27

In addition to what davekw7x have shown, below is another example on the looping.

CPP / C++ / C Code:

typedef enum 
{
   test_1 = 1, 
   test_2 = 2, 
   test_3 = 3, 
   test_End

} testENUM;

int main ( void )
{
   int i = 0;

   for( i = test_1; i < test_End; i++ )
   {
      printf( "i = %d\n", i );

   }

   return 0;
}

Hope this helps!!!

Spidy08 · #4 02-Oct-2007, 07:32

Thanks a lot Dave..

I was trying to do the i++, didn't think of casting the i+1 to myenum type.

)

davekw7x · #5 02-Oct-2007, 09:33

Quote:

Originally Posted by Spidy08

I was trying to do the i++, didn't think of casting the i+1

This highlights some of the differences between enums in C and enums in C++. See footnote.

In C, enums are merely a notational convenience for named integers. (That is, an enum is actually an int data type.)

In C++ enums are their own data type with a few interesting features:

1. There are no '+' or '++' or other arithmetic operators for enums in C++ (So, if i is an enum data type you can't simply say i++.)

2. In arithmetic expressions involving ints and enum data types, the enum data variables are "promoted" to ints, so the expression i+1 promotes i to an int and adds 1. The result is an int.

3. In C++ you can't assign an integer value to an enum variable without a cast. I used function-style cast, but you could use a C-style cast or a C++ static cast.

Regards,

Dave

Footnote:
In C, if i is your enum data type you could simply use

CPP / C++ / C Code:

for(i = a; i <= e; i++) {

and no casting would be required.

#6 02-Oct-2007, 10:44

Quote:

Originally Posted by davekw7x

This highlights some of the differences between enums in C and enums in C++.

...yet another reason why C++ is not a superset of C.

:davis:

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