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I was looking at this site: http://rosettacode.org/wiki/Fibonacci_sequence#JavaScript and saw this program:
function fib(n) {
return function(n,a,b) {
return n>0 ? arguments.callee(n-1,b,a+b) : a;
}(n,0,1);
}
How does this work, what are those two arguments (a and b) help. I traced it and still can't figure out how this works
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Write a tail recursive function for calculating the n-th Fibonacci number. A recursive function is tail recursive when the recursive call is the last thing executed by the function. Recommended: Please try your approach on {IDE} first, before moving on to the solution.
The function fibonacci is called recursively until we get the output. In the function, we first check if the number n is zero or one. If yes, we return the value of n. If not, we recursively call fibonacci with the values n-1 and n-2.
The famous Fibonacci sequence. This famous sequence is recursive because each term after the second term is the sum of the previous two terms.
Definition: A special form of recursion where the last operation of a function is a recursive call. The recursion may be optimized away by executing the call in the current stack frame and returning its result rather than creating a new stack frame.
In the function(n,a,b), n serves as a countdown counter, and a b stores two consecutive Fibonacci numbers for the purpose of computing the next, so when n reaches 0, you have a as the n+1-th Fibonacci number (since the real Fibonacci has two 1s as the beginning).
E.g., n=4:
n a b
4 0 1
3 1 2
2 2 3
1 3 5
0 5 8
As you can see, the value of a and b always equal to the Fibonacci numbers. Also, this is very similar to Functional Programming (as the website stated Scheme programmers).
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