## Is a function still recursive if you don't use return?

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I wrote the following code, which works for calculating Fibonacci sequences:

arr = [0] i = 1 def get_fib(position): if position == 0: return arr[0] if position > 0: global i arr.append(i) i = i + arr[-2] get_fib(position - 1) return arr[position]

Is this still recursion, even though I don't use return before get_fib? Do I need to include return for a function to be recursive?

The function is recursive because it calls itself. So, no, technically you don't need to return the value from that call for it to be recursive.

However, for the function to work, you do. Consider this example:

def factorial(n): if n == 0: return 1 else: return factorial(n-1) * n

This is the same as:

def factorial(n): if n == 0: result = 1 else: result = factorial(n-1) * n return result

What do you think would happen if we change the next to last line to just:

factorial(n-1) * n

Now there is no longer a `result`

being assigned and the function will probably fail, claiming `result`

has no value. If we change the original in a similar way:

def factorial(n): if n == 0: return 1 else: factorial(n-1) * n

It would calculate `factorial(n-1) * n`

, but it would simply discard the result and since there is no statement after it, the function would return (!) without a return statement, returning `None`

instead.

**Recursion and stack,** In its simplest form, a recursive function is one that calls itself. If recursion still doesn't seem simple to you, don't worry: I'm going to go over a� select 0–500 with recursive function A simple use case. The above examples can be observed as a simple use case. It does not involve large tables, neither complex operations nor table joining.

Yes the function is recursive, by definition, because it calls itself. Where the call to `return`

is placed is not what determines whether or not the function is recursive. However, if you write a recursive function, it must return *at some point* (known as the "base case"), because if it doesn't it will cause infinite recursion, which will throw an exception ("*Runtime Error: maximum recursion depth exceeded*") once you pass the Python interpreter's max recursion limit.

**How Recursion Works — Explained with Flowcharts and a Video,** If one of the immediate components belongs to the same class of data as the input, the function is recursive. For that reason, we� For the Love of Physics - Walter Lewin - May 16, 2011 - Duration: 1:01:26. Lectures by Walter Lewin. They will make you ♥ Physics. Recommended for you

Consider two examples:
**Example 1:**

>>> def fun_a(): ... fun_a()

This is a simple function that, calls itself. This function has no terminating condition (the condition when it has to stop calling itself and start popping the stack contents that was build up during the call to itself). This is an example of infinite recursion. If you execute such function, you'll get an error message similar to this:

Traceback (most recent call last): File "<stdin>", line 1, in <module> File "<stdin>", line 2, in fun_a File "<stdin>", line 2, in fun_a File "<stdin>", line 2, in fun_a [Previous line repeated 995 more times] RecursionError: maximum recursion depth exceeded

**Example 2:**

>>> def fun_b(n): ... if n == 0: ... return ... fun_b(n-1)

In this case, even though the function is calling itself over and over again, but there is a termination condition, that will stop the function from calling itself again. This is an example of finite recursion and we say that the recursion unfolds on the base case (here base case is when the value of `n`

becomes `0`

).

To conclude, this is what we say is the general format of a finite recursion. The base case and the recursive call should be in the same order as mentioned here. Otherwise, the function will never stop calling itself and will lead to infinite recursion.

function_name(parameters) base case recursive call

**Recursion (computer science),** So that if a function receives the following nested arrays: iterative solution, but it's way more complicated because we would have to nest for loops but don't know how deep they are nested. But we still have places to go. C Programming & Data Structures: How to write Recursive Functions in C Language. Topics discussed: 1) Steps to write Recursive Procedures. 2) Example of recursive function. C Programming Lectures

A function can be recursive even if there is no return statement. A classic example is the `inorder`

traversal of a binary tree. It doesn't have a return statement. The only requirement for a function to be recursive is that it should call itself. Below is the code (in C).

void inorder(struct node* root) { if (root) { inorder(root->left); printf("%d", data); inorder(root-right); } }

**Dijkstra was right — recursion should not be difficult,** A recursive function is defined in terms of base cases and recursive steps. You can step through the computation to see the recursion in action. in your recursion, don't change the original spec of your method, and don't force your clients to We have still effectively reduced the problem by reducing it to positive integers. In-direct Recursive function. 3. Tail Recursive function. 4. Non-tail Recursive function. We’ll discuss each one in separate video tutorials. In this video tutorial lets learn the very basic of how to write and use recursive functions and how to keep track of function instances and return data. Requirements To Learn Recursion. 1. You need to

**Reading 14: Recursion,** A() is a recursive function since it directly calls itself. The second part of the defintion refers to a cycle (or potential cycle if we use conditional Don't be concerned if you have trouble with some of these functions, many more examples will be� The difference is that with recursive functions, you rarely have to modify any variable --you just pass the new values as parameters to the next function call. This allows you to keep all of the benefits of not having an updateable variable while still having repetitive, stateful behavior. Converting a common loop to a recursive function. Let

**Recursive Functions,** Recursion is associated strongly with functional programming. We do What if you have two functions that call each other? You can still do it. I have a friend who would say, “Well, I don't like Lisp because there's no loops. If you still don't know what recursion is, read this sentence. Haha! Just kidding! Recursion is actually a way of defining functions in which the function is applied inside its own definition. Definitions in mathematics are often given recursively. For instance, the fibonacci sequence is defined recursively.

**What is recursion and when should I use it?,** Recursive Functions in Python; Maintaining State; Recursive Data Structures in But if we keep chipping away at them, more often than not we can break them down into Also, Python's mutable data structures don't support structural sharing, However, when I tried that, it still didn't print 00, 01, 02, etc. as you specified. On every recursive call, I create 2 new recursive calls on the left subtree and the right subtree to traverse the nodes and check that their values are correct. I want to calculate BigO of this. I think that in the worst case it is O(n) because if it IS a Heap, then it never stops early and needs to visit every node.

##### Comments

- "Recursive" just means the function calls itself (directly or indirectly), nothing to do with returns. Your function is recursive.
- There is no Python function without return (there is an implicit
`return None`

) or exception.