Essential C++

2.4. Using Local Static Objects

Our fibon_seq() function of Section 2.2 calculates a Fibonacci sequence of a user-specified size with each invocation, returning a vector holding the elements. That is a bit more work than is necessary.

We really need only one Fibonacci sequence vector. The elements, after all, are invariant. The only thing that changes from one call of fibon_seq() to the next is the number of elements the user wishes to have available. Consider the following three invocations of fibon_seq():

fibon_seq( 24 ); 
fibon_seq( 8 ); 
fibon_seq( 18 ); 

The first call calculates all the values necessary to fulfill the request of the second and third invocations. If a fourth invocation requested 32 elements, we really need calculate only ...