Tail recusion and tail recursive elimination

Rahul S
2 min readApr 10, 2023
src: GeeksforGeeks

Tail recursion and tail call elimination are two related concepts in computer science that are often used together to optimize recursive functions.

Tail Recursion:

Tail recursion is a specific form of recursion where the last operation of a function is a recursive call. This means that there are no operations to be performed after the recursive call, and the function can simply return the result of the recursive call without any additional computation.

Here’s an example of a tail-recursive function to calculate the factorial of a number:

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

In this example, the recursive call to factorial is the last operation in the function. When the function is called with a non-zero value for n, the function simply returns the result of the recursive call multiplied by the current value of acc. This is an example of tail recursion because there are no additional operations to be performed after the recursive call.

Tail recursion is important because it allows for the optimization of recursive functions. When a function is tail-recursive, it can be easily optimized by a compiler or interpreter to eliminate the use of the call stack, which can improve performance and reduce memory usage.

Tail Call Elimination:

Tail call elimination, also known as tail call optimization, is a technique used by compilers and interpreters to optimize tail-recursive functions. The basic idea behind tail call elimination is to convert a tail-recursive function into an iterative loop that performs the same computation as the recursive function.

Here’s an example of how a tail-recursive function can be transformed into an iterative loop using tail call elimination:

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

can be transformed into:

def factorial(n):
acc = 1
while n > 0:
acc *= n
n -= 1
return acc

In this example, the tail-recursive function has been transformed into an iterative loop that performs the same computation. By doing so, the use of the call stack has been eliminated, and the function can be executed more efficiently.

Overall, tail recursion and tail call elimination are important concepts in computer science that can be used to optimize recursive functions. By using these techniques, recursive functions can be transformed into more efficient and memory-efficient algorithms.

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