B4J Question Random Float Numbers ??

[behnam_tr]

I didn't find any method to generate Random Float numbers between 0 and 1
Is there such a method?

i need simulate this java script code

Math.floor((Math.random() * 10000000)+1);

Math.random() in java script >>> 0.1142937586695465 , 0.9373901332670653 , 0.7550847537693961

 

[LucaMs]

I thought a solution might be to divide 1 by a random integer.
The weird thing is that 1/MaxInt returns 0.00000000046566128730773926 (those many zeros)

Dim MaxInt As Int = Power(2, 31)
Dim RndValue As Double
Dim flt As Float

RndValue = Rnd(1, MaxInt)
    Log("rndValue: " & NumberFormat2(RndValue, 1, 0, 0, True))
flt = 1/ RndValue
    Log(NumberFormat(flt, 1, 26))

 

[William Lancee]

'Use:     Log(NumberFormat2(rndFloat(0, 1, 8), 1, 8, 8, False))
Private Sub rndFloat(minVal As Float, maxVal As Float, numDecimals As Int) As Float
    Dim multiplier As Float = Power(10, numDecimals)
    Dim rndNum As Int = Rnd(Floor(minVal * multiplier), Floor(maxVal * multiplier))
    Return rndNum / multiplier
End Sub

 

[agraham]

The weird thing is that 1/MaxInt returns 0.00000000046566128730773926 (those many zeros)

Why is that weird? That seems to be the expected value or am I missing something?

 

[LucaMs]

weird

I didn't think much, very little indeed, and didn't do the 1/MaxInt calculation any other way.
It is precisely the concept that was wrong. The classic RND function, as you know, returns a decimal number between 0 and 1, and the function I wrote on the fly, mindlessly, can't do that.
Even the one written by @William Lancee does not correspond to the classic one.

 

[LucaMs]

I could be wrong again but it seems to me that to get the classic decimal function (values between 0 and 1) the following code is sufficient:

Public Sub RNDFloat As Float
    Dim intRnd As Int = Rnd(0, 2147483647)
    Return intRnd / 2147483647
End Sub

 

[Daestrum]

Using javaObject

    Dim rf As JavaObject
    rf.InitializeNewInstance("java.security.SecureRandom",Null)   ' the null can be a Long as the seed
    For a = 0 To 10
        Log(rf.RunMethod("nextFloat",Null))
    Next

 

[behnam_tr]

Updated post #1

 

[William Lancee]

Rather than changing the question it would be better to start a new one.
Javascript

Math.floor((Math.random() * 10000000)+1);

B4X

Rnd(1, 10000001)

 

[IHZ]

You can solve your problem by inserting the following code:

' Returns a random Double between 0.0 and less 1.0
' This function is similar to Java Math.random()
Private Sub Math_random As Double
Private maxint = 0x7fffffff As Int
    Return Rnd(0,maxint)/maxint
End Sub

Private Sub YourFunc As Double
    Return Floor(((Math_random * 10000000)+1))
End Sub

The subroutine "YourFunc" is just to show, how to use it together with code

Best regards
Hermann