# LabVIEW

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## Incorrect Multiply Result?

I'm doing the following, and received the wrong value. Is there something I'm missing?

Message 1 of 7
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## Re: Incorrect Multiply Result?

Why is this incorrect?

anything x 0 = 0 and -0 = 0

Message 2 of 7
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## Re: Incorrect Multiply Result?

To prove that -0 is equal to 0, add an increment by 1 after the multiply and before your indicator.  The math is correct, it may just look wonky.

Message 3 of 7
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## Re: Incorrect Multiply Result?

I mean it makes sense. The reason why I ask is because problem arises when I try to convert this is an string which now becomes "-0". Doing any comparisons fails immediately. Is there a reason why LV does this, rather than follow -1 * 0 = 0?

Message 4 of 7
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Accepted by Tom321

## Re: Incorrect Multiply Result?

Well, there is a sign bit in the IEEE754 specification.  When multiplying, the two sign bits should just be XORed.  -1 has a sign of 1 (negative) while 0 has a sign of 0 (positive).  XOR the values and you get 1 (negative).  This results in -0.

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Message 5 of 7
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## Re: Incorrect Multiply Result?

@Tom321 wrote:

Doing any comparisons fails immediately.

Define "fail". If you do the comparison on the numerics, you can see that -0 and 0 are equal as expected.

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## Re: Incorrect Multiply Result?

@altenbach wrote:

@Tom321 wrote:

Doing any comparisons fails immediately.

Define "fail". If you do the comparison on the numerics, you can see that -0 and 0 are equal as expected.

Tom321 did sort of define it.  He stated that he converts to a string and then does comparisons.

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Message 7 of 7
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