Recursive factorial program in perl

By definition, the factorial of a positive integer number N is a product of all the integers numbering from 1 to N, including N. In Perl 6, this can be easily expressed with the use of a reduction operator:.

Another approach to calculating factorials is using recursion according to the formula: n! On each iteration step, the function calls itself with decremented argument and should stop as soon as the value becomes less than two. In Perl 6, the knowledge of the fact that 1!

Multi-functions are subroutines prefixed with the multikeyword. They all share the name but may be distinguished by the type, number or values of their arguments. For the factorial, define two multi-functions, one to calculate the factorial of the smallest numbers 0 and 1 ignore the negative numbers for now :. Perl provides us with the flexibility to use subroutines both iteratively and recursively.

A simple example showing the use of recursive subroutine in Perl would be that calculating the factorial of a number. Example :! Traversing a directory tree means to iterate over or to print each file and sub-directories within a root directory. The directory tree is a representation of the sub-directories and files within sub-directories and other files within the directory in the form of a tree denoting the parent-child relationship between these directories and respective files.

Both Unix and Windows systems organize file directories into a tree structure. Although in Perl, traversing a directory tree or walking a directory tree can be done both iteratively and recursively, but we often use the later one when the number of files or sub-directories inside our root folder is very large.

This is because of the fast and less number of lines of code written in recursive function in comparison to an iterative one. The later is used when the corresponding number of files are less in number.

Recursively Traversing a Directory Tree The problem with the iterative solution of traversal apart from its slow speed and more lines of code is the fact that all the sub-directories within the root directory must have the same orientation and the same number of files within them. Otherwise, the traversal can become a complex task. Probably the only escape from this is to click on the definition of recursion in Wikipedia.

Written by Gabor Szabo. If you have any comments or questions, feel free to post them on the source of this page in GitHub. Source on GitHub. Comment on this post. Gabor can help refactor your old Perl code-base. He runs the Perl Weekly newsletter. Related Articles. Table of Contents. Improve Article. Save Article. Like Article.

Last Updated : 27 Jun, Perl Program to calculate Factorial. Recursively calling function with the next value. Function call and printing result after return. Perl Program to print Fibonacci series. Retrieving values from the parameter.