Recursions are no alien feature to any programmer worth his salt. Recursions are leveraged in functional programming to accomplish iteration/looping. Recursive functions invoke themselves, performing an operation repeatedly till the base case is reached. Tail call-based recursions are a common phenomenon. Recursion typically involves adding stack frames to the call stack, thus growing the stack. You can run out of stack space during deep recursions. The compiler does its own share of optimizations (predominantly tail call optimization/elimination) to conserve stack space and improve throughput. But the functional world (with its first-class and higher-order functions) gives us more flexibility to wire such optimizations in our recursive functions. Let's see how this is achieved with the following factorial example:
//Regular Recursion
Func<int, int> factorial = (n) =>
{
Func<int, int> fIterator = null; //Work-around for ...