Factorial in Every Language

Welcome to the Factorial page! Here, you’ll find a description of the project as well as a list of sample programs written in various languages.

Description

The factorial of an integer n is defined as:

n! = 1 x 2 x 3 x 4 x ... x n

With the special case 0! = 1.

Requirements

You must write an executable program that accepts an integer n on standard input via the command line, and outputs n! to standard output.

Note that the factorial function grows very quickly. For example, 4! = 24 but 8! = 40320. Therefore, you should impose a limit on the input, so that the largest factorial still fits into your language’s largest supported datatype.

Also note that the factorial is not defined for negative integers.

Testing

Some tests for your program are:

Description	Input	Output
No input		“Usage: please input a non-negative integer”
Empty input	””	“Usage: please input a non-negative integer”
Invalid Input: Not a number	“asdf”	“Usage: please input a non-negative integer”
Invalid Input: Negative integer	-1	“Usage: please input a non-negative integer”
Sample Input: Zero	0	1
Sample Input: One	1	1
Sample Input: Four	4	24
Sample Input: Eight	8	40320
Sample Input: Ten	10	3628800

Articles

• Factorial in Algol68
• Factorial in Bash
• Factorial in C
• Factorial in C#
• Factorial in C++
• Factorial in Cobol
• Factorial in Coffeescript
• Factorial in D
• Factorial in Elixir
• Factorial in Erlang
• Factorial in Fortran
• Factorial in Go
• Factorial in Groovy
• Factorial in Haskell
• Factorial in Java
• Factorial in Javascript
• Factorial in Julia
• Factorial in Kotlin
• Factorial in Lisp
• Factorial in Lua
• Factorial in Mathematica
• Factorial in Matlab
• Factorial in Objective C
• Factorial in Perl
• Factorial in Php
• Factorial in Python
• Factorial in R
• Factorial in Rust
• Factorial in Scala

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