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Thread: [RESOLVED] Can't borrow Long DataType from VB.Net directly into VB6

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    Resolved [RESOLVED] Can't borrow Long DataType from VB.Net directly into VB6

    Hi guys

    I just realized Long in V6 is much smaller than VB.Net ie -2,147,483,648 to 2,147,483,647 vs -9,223,372,036,854,775,808 through 9,223,372,036,854,775,807. This has created a VB6 code copied from VB.Net to calculate a number to become zero due to overflow. Once i switch to Double in VB6 it is ok. Did i now get it right?

  2. #2
    PowerPoster Arnoutdv's Avatar
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    Re: Can't borrow Long DataType from VB.Net directly into VB6

    You could also use the Currency datatype
    Currency variables are stored as 64-bit (8-byte) numbers in an integer format, scaled by 10,000 to give a fixed-point number with 15 digits to the left of the decimal point and 4 digits to the right.
    This representation provides a range of -922,337,203,685,477.5808 to 922,337,203,685,477.5807.
    The type-declaration character for Currency is the at sign (@).

    The Currencydata type is useful for calculations involving money and for fixed-point calculations in which accuracy is particularly important.

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    Re: Can't borrow Long DataType from VB.Net directly into VB6

    Pass max and min values from .net to vb
    And see how the vb data types handle them it will literally tell you if there is still a problem. If you don’t need to do math on them just pass them as a string or do all your math on the .net side working with strings of digits coming from vb

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    Angel of Code Niya's Avatar
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    Re: [RESOLVED] Can't borrow Long DataType from VB.Net directly into VB6

    VB6 lacks a 64 bit integer type. However, a Double is 64 bits. If all you care about is range, then a Double may and I stress may suffice as a substitute. I'm not sure about the how much difference there is in the range differences between a 64 bit integer and a Double, I've never examined it. But if you also care about the bitwise representation then you're going to find yourself in problems. If the bitwise representation is important, then a better option is to be clever by using combining two 32 bit integers.
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    PowerPoster Elroy's Avatar
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    Re: [RESOLVED] Can't borrow Long DataType from VB.Net directly into VB6

    It's not so much about "range" as it is about "accuracy" (significant digits). A LongLong has far more "accuracy" than a Double, but it has far less "range". That's the tradeoff (with both being 8 bytes).

    If you're careful about it, you actually can get a LongLong (via a Variant) into VB6. But typically, a Currency works quite nicely for these purposes, as it's actually a LongLong with a forced decimal at the fourth place.
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    Re: [RESOLVED] Can't borrow Long DataType from VB.Net directly into VB6

    Depending on what you are really doing that is putting your calculations over the edge you might also find this useful:

    MulDiv function

    Note that it has a weird bug though:

    What is the historical reason for MulDiv(1, -0x80000000, -0x80000000) returning 2?

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