CS253 IQ 07

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What problem do virtual functions deal with?

1. Fireball
2. Invisibility
3. Polymorphism
4. Regeneration
5. Simulacrum

Which of these is correct?

class Base { };
class Derived : public Base { };
Base *b = …;
Derived *d = …;

1. b = dynamic_cast<Base *>(d);
2. b = dynamic_cast(Base *, d);
3. b = dynamic_cast(d);
4. d = dynamic_cast(b);
5. d = dynamic_cast<Derived *>(b);
6. d = dynamic_cast(Derived *, b);

Any problems with this code?

#ifndef FOO_H_INCLUDED

#include "otherfile.h"
#include <string>
class Foo {
   …
};

#define FOO_H_INCLUDED
#endif

1. It’s fine.
2. The #ifndef should be #ifdef.
3. The define is in the wrong place.
4. It’s unnecessary—include guards are no longer required in modern compilers.

Bit Manipulation

What’s the best way to find out if bit #7 (where bit #0 is the LSB) of the int v is set?

1. if (v.bit(7))
2. if (v & 00000080)
3. if (v && (1 << 7))
4. if ((v>>7) & 01)
5. if ((v<<24) < 0)