Bug in equality checks? 28.15e-3 == 28.15/1000 false

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Gustavo Lunardon
Gustavo Lunardon 2021-10-15
评论： Paul 2021-10-15
Ran in:
Why does this happen? It does not regocnize equality on 7.48e-3 == 7.48/1000, but it does on 7.47e-3 == 7.47/1000 as well. Another example below.
28.1e-3 == 28.1/1000
ans = logical
1
28.15e-3 == 28.15/1000
ans = logical
0

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Star Strider
Star Strider 2021-10-15
Wellcome to the world of floating-point approximation error!
See Why is 0.3 - 0.2 - 0.1 (or similar) not equal to zero? and Floating-Point Numbers
This is roughly equivalent to expressing in decimals. The result is 0.3 an infinite number of 3 following it, never being excactly equal to .
.
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Image Analyst
Image Analyst 2021-10-15
I think the abs() is needed because one quantized expression could be above or below the other quantized expression, and I don't think you'd know which it will be in general.
Paul
Paul 2021-10-15
Exactly and well said. I should have included a statement to that effect in my comment

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Image Analyst
Image Analyst 2021-10-15

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