Re: Print numbers
On Jul 7, 12:46 pm, arnuld <sunr...@invalid.address> wrote:
On Mon, 07 Jul 2008 02:40:44 -0700, James Kanze wrote:
But that looks like the start of a Fibonacci sequence. If
so, and you want to output an arbitrary number of elements,
you'll need something like:
std::cout.setf( std::ios::fixed, std::ios::floatfield ) ;
std::cout.precision( 0 ) ;
double sqrt5( sqrt( 5.0 ) ) ;
double psi( (1.0 + sqrt5) / 2.0 ) ;
for ( int i = 1 ; i <= count ; ++ i ) {
if ( i != 1 ) {
std::cout << ',' ;
}
std::cout << (pow( psi, i ) - pow( -psi, -i )) / sqrt5 ;
}
std::cout << '\n' ;
I did not know that OP was looking for a Fibonacci sequence. I
just did it this way:
/* a program to print the sum of last 2 numbers.
Which is the definition of a Fibonacci sequence.
The "classical" implementation is:
int
fib( int n )
{
return n <= 0 ? 1 : fib( n - 1 ) + fib( n - 2 ) ;
}
It's sometimes used as a good example of when not to use
recursion:-); if you just want a few specific values, and add a
cache, however, it's not that bad:
int
fib( int n )
{
static std::vector< int > cache( 2, 1 ) ;
if ( n >= static_cast< int >( cache.size() ) ) {
cache.push_back( fib( n - 1 ) + fib( n - 2 ) ) ;
}
return n < 0 ? 1 : cache[ n ] ;
}
Both such solutions suffer from the fact that int's overflow for
very small values of n, however. My solution above doesn't.
and it prints fine, except that it puts a comma at the end
Which is a separate (and general) problem: how to format
sequences of data.
and I have out a limit of 10 numbers:
Try outputting 100 values, and see what happens.
--
James Kanze (GABI Software) email:james.kanze@gmail.com
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