Wish Bit.ToBinaryString2

udg · Nov 1, 2021

Hi,
I'd like an additional function that returns the complete string of bits instead of just the significant ones.
Something like:

B4X:

Sub ToBinaryString2(N As Int) As String
    Dim filler As String = "00000000000000000000000000000000"
    Dim sTest As String = Bit.ToBinaryString(N)
    Return filler.SubString(sTest.Length)&sTest
End Sub

To return from that string representation to its original Int value ,we already have function ParseInt. so

B4X:

Log(Bit.ParseInt(ToBinaryString2(test),2))

Note: unexpectedly ParseInt fails for negatives. For example:

B4X:

Dim test As Int = -2
Dim s As String = Bit.ToBinaryString(test)
Log(Bit.ParseInt(s,2))

Why did I post this wish? I was studying class B4xBitSet (which I like it a lot) and wanted to save the "block" entries (which for B4A/J are Ints) to their BinaryString representation in order to then save them in a Text field (or similar) in a database.
I'm aware of a function that returns booleans for each bit in the set in order to then use the Serializator, but once the set data array will be exposed (it will be a separate wish) it will be easier to put all the "blocks" together in a long string (and viceversa).

udg

Erel · Nov 2, 2021

You don't need anything special to create such a string.

B4X:

Sub ToBinaryString(set As B4XBitSet) As String
    Dim sb As StringBuilder
    sb.Initialize
    For i = set.Size-1 To 0 Step -1
        sb.Append(IIf(set.Get(i), "1", "0").As(String))
    Next
    Return sb.ToString
End Sub

udg · Nov 2, 2021

Thanks Erel. The idea behind my wish was to make it available as a standard provision for Bit.
I know that we can "extract and modify" code published as b4xlibs.

Anyway, what about the ParseInt function when using negatives? I repeat here the code in case you missed it:

B4X:

Dim test As Int = -2
Dim s As String = Bit.ToBinaryString(test)
Log(Bit.ParseInt(s,2))

This code fails with error:
java.lang.NumberFormatException: For input string: "11111111111111111111111111111110"

udg

Erel · Nov 2, 2021

udg said:
The idea behind my wish was to make it available as a standard provision for Bit.

Converting the bit set to a string is an esoteric feature. B4XBitSet is expected to be used with large sets. In such cases it doesn't make sense to convert the data to a string.
If you need it then use the code I posted.

udg said:
Anyway, what about the ParseInt function when using negatives?

This is related to the way the underlying numeric parser works. You can use this code instead:

B4X:

Sub ParseSignedBinary (s As String) As Int
    If s.Length = 32 And s.CharAt(0) = "1" Then
        Dim i As Int = Bit.ParseInt(s.SubString(1), 2)
        Return 0x80000000 + i
    Else
        Return Bit.ParseInt(s, 2)
    End If
End Sub

udg · Nov 2, 2021

Converting the bit set to a string is an esoteric feature. B4XBitSet is expected to be used with large set

I see your point and I agree. For large sets it will be mostly unusable.

This is related to the way the underlying numeric parser works.

Maybe a note of caution on ParseInt hint text would be useful.
I can understand the difficulty when designing the language and its "core" libs, whether to strictly adhere to java signed data types versus a more general bit manipulation paradigm.
Anyway, the good news is that we always have a solution handy

Thank you again

Wish Bit.ToBinaryString2

udg

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Erel

B4X founder

udg

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Erel

B4X founder

udg

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Wish Bit.ToBinaryString2

udg

Expert

Erel

B4X founder

udg

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Erel

B4X founder

udg

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