# Re: An kind of member function name scope specification

From:
blargg.ei3@gishpuppy.com (blargg)
Newsgroups:
comp.lang.c++
Date:
Sun, 26 Apr 2009 17:18:11 -0500
Message-ID:
<blargg.ei3-2604091718110001@192.168.1.4>
Stefan Ram wrote:
[snip oddly-formatted useless Account class]

Is such an account class is a good example for teaching?

I need the first example to be very simple, yet it needs
to suggest to be useful and related to applications of
the language.

Are there any other good examples of classes, that are

- small and simple
- not already part of the standard library
- not requiring special knowledge of a field
- looking somewhat natural and useful

?

Here's a simple example I just wrote that performs a clearly useful
encapsulation of the Fibonacci sequence. Any student can understand
the sequence, and how hiding the details simplifies the client code in
main(). The constructor performs an important function, and it shows
the use of const versus non-const. I felt that using operator
overloads (++ and operator ()) weren't appropriate. I took some
liberty with whitespace, showing how when something is short and
trivial, one might use fewer newlines.

#include <iostream>

class Fibonacci {
int a, b;
public:
Fibonacci();
int value() const { return a; }
void next();
};

Fibonacci::Fibonacci() : a( 0 ), b( 1 ) { }

void Fibonacci::next()
{
int fib = a + b;
a = b;
b = fib;
}

int main()
{
Fibonacci f;
for ( int n = 10; n--; )
{
std::cout << f.value() << ',';
f.next();
}
std::cout << '\n';
return 0;
}

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