Android Code Snippet Factorial Function (!n)

ilan · Apr 16, 2019

i had to get the factorial of a number but could not find a buildin function in b4x so i created a function for that.

B4X:

Sub factorial(number As Int) As Int
    Dim returnNr As Int = number
    Do Until number <= 1
        number = number - 1
        returnNr = returnNr * number
    Loop
    Return returnNr
End Sub

use:

B4X:

Log(factorial(6))

log: 720

Erel · Apr 16, 2019

Your code is better but it is still worth posting the recursive version as it is quite nice:

B4X:

Sub Factorial(Number As Int) As Int
 If Number = 1 Then Return 1
 Return Number * Factorial(Number - 1)
End Sub

ilan · Apr 16, 2019

Erel said:
Your code is better but it is still worth posting the recursive version as it is quite nice:

B4X:

Sub Factorial(Number As Int) As Int If Number = 1 Then Return 1 Return Number * Factorial(Number - 1) End Sub

really cool, i didnot knew that it is possible to do that with b4x. very smart coding

JordiCP · Apr 16, 2019

As factorial is defined for n>=0 but still 0!=1, it should be (for non-negative numbers)

B4X:

Sub Factorial(Number As Int) As Int
 If Number=0 Then Return 1
 Return Number * Factorial(Number - 1)
End Sub

advansis · Apr 22, 2019

I prefer non-recursive functions, in this case is very simple to enroll it. Recursive functions increase memory and stack usage. Recursion in very elegant, but, in my own opinion, usually are not efficient

Erel · Apr 23, 2019

advansis said:
Recursion in very elegant, but, in my own opinion, usually are not efficient

You cannot talk about efficiency without a real context. It doesn't matter whether a task takes 0.2ms or 0.4ms. Recursion is a very important tool. Like all tools it has its advantages and disadvantages.

advansis · Apr 28, 2019

Erel said:
You cannot talk about efficiency without a real context. It doesn't matter whether a task takes 0.2ms or 0.4ms. Recursion is a very important tool. Like all tools it has its advantages and disadvantages.

You are right, Erel. Anyway, when possible I prefer the straigth-way. ;-) Recursion is sometimes misused

Android Code Snippet Factorial Function (!n)

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