B4R Question DoublesFromByte quesiton

janderkan

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• Jul 7, 2020

• #2

B4X:

Dim Height(5) as Byte
...   
...   
...
    Dim BC As ByteConverter
    Dim dHeights() As Double
    dHeights = BC.DoublesFromBytes(Height)
    Dim dHeight As Double = dHeights(0)

 

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emexes

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• Jul 7, 2020

• #3

daveinhull said:

B4X:

Dim Height(5) as Byte

Click to expand...

Are Doubles 5 bytes in B4R? Applesoft Basic déjà vu.

 

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janderkan

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• Jul 7, 2020

• #4

No it is 4 bytes, you can see it here https://www.b4x.com/android/forum/threads/data-types.65666/#content

 

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daveinhull

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• Jul 7, 2020

• #5

Hi,

Many thanks for the reply and it now compiles, but I'm not getting the right result.
Ok, so maybe I've misunderstood what DoublesFromBytes means.
I have a byte array with 5 bytes containing ASCI characters that represent a floating point number, say 34.1 (so 51,50,46,49,00) and I was assuming that it would convert this to a 4 byte numeric value representing the double value, but I get 0.0000 if I log it

Thanks
Dave

 

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janderkan

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• Jul 7, 2020

• #6

B4X:

    Dim bytes() As Byte = Array As Byte(51,50,46,49,00)
    Dim Height As Double = bc.StringFromBytes(bytes)
    Log(Height)

 

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daveinhull

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• Jul 7, 2020

• #7

Perfect! Many thanks, although I must admit I'm totally confused with all the conversions that are going on - I guess I'll get their.

 

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janderkan

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• Jul 7, 2020

• #8

Remember to 'like'

 

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NoNickName

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• Jul 7, 2020

• #9

A double is something different than a string literal.

 

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daveinhull

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• Jul 7, 2020

• #10

Hi, yes I know that which is why I was thinking the function DoublesFromBytes would do the conversion. Apparently its StringFromBytes which must create a string representation of the double and then somehow assigning a string of a double to a double variable does the conversion. I get this with a constant but not with an variable. In other languages doing something like:
A ="12.3"
B = A
Where A is a string and B is a double wouldnt work.

 

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emexes

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• Jul 7, 2020

• #11

A useful relevant function:

 

Last edited: Jul 8, 2020

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NoNickName

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• Jul 8, 2020

• #12

Anyway, please note your example: 34.1 (51,50,46,49,00) is actually 32.1 with a trailing nul char that can safely be omitted

 

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