| Pattern 12 | Tail Recursion |
Intent
To repeat a computation without using mutable state and without overflowing the stack
Overview
Iteration is an imperative technique that requires mutable state. For example, let’s examine a trivial problem, writing a function that will calculate the sum from one up to an arbitrary number, inclusive. The code below does just that, but it requires both i and sum to be mutable:
| JavaExamples/src/main/java/com/mblinn/functional/tailrecursion/Sum.java | |
| | public static int sum(int upTo) { |
| | int sum = 0; |
| | for (int i = 0; i <= upTo; i++) |
| | sum += i; |
| | return sum; |
| | } |
Since the functional world emphasizes immutability, iteration is out. In its place, we can use recursion, which does not require immutability. ...
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