B4J Code Snippet Return Rnd number in step mode

If you would like to get a random number between 2 values but in step mode like get from 0 to 20 only an even number you can do it like this:

EDIT: see post #6: https://www.b4x.com/android/forum/threads/return-rnd-number-in-step-mode.68822/#post-436627

 

[Erel]

Another implementation:

'Returns a random number between Min (inclusive) Max (exclusive!) Step (Stp number)
Sub RndStep(Minimum As Int, Maximum As Int, Stp As Int) As Int
   Dim i As Int = Rnd(Minimum, Maximum)
   i = i - ((i - Minimum) mod Stp)
   Return i   
End Sub

Your code can be problematic. It will be very slow if the possible range of numbers is large (time and space complexity of O(n) where n is the range, my solution complexity is O(1)).

 

[ilan]

Ok this is smart @Erel

EDIT: but wrong

Log(RndStep(5,20,2))

when i get number 8 then

i = i - ((i - Minimum) mod Stp)

i = 8 - ((8-5) mod 2) = 7

return 7

and 7 is not an even number!

 

[ilan]

maybe thats the solution:

'Returns a random number between Min (inclusive) Max (exclusive!) Step (Stp number)
Sub RndStep(Minimum As Int, Maximum As Int, Stp As Int) As Int
   Dim i As Int = Rnd(Minimum, Maximum)
   i = i - (i mod Stp)
   If i < Minimum Then i = i + Stp
   Return i 
End Sub

 

[Erel]

and 7 is not an even number!

It is based on your implementation. It starts from the minimum and adds the step multiple times. So 7 is a valid number.

If you want to start the series of allowed numbers from 0 instead of the minimum:

'Returns a random number between Min (inclusive) Max (exclusive!) Step (Stp number)
Sub RndStep(Minimum As Int, Maximum As Int, Stp As Int) As Int
   If Minimum Mod Stp <> 0 Then Minimum = (Floor(Minimum / Stp) + 1) * Stp
   Dim i As Int = Rnd(Minimum, Maximum)
   i = i - (i mod Stp)
   Return i  
End Sub

 

[ilan]

It is based on your implementation. It starts from the minimum and adds the step multiple times. So 7 is a valid number.

you are right my code was wrong i wanted to get only a number in the range between min and max that divides by step