Rounding in Matlab (very trivial)

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Ryan Shrott
Ryan Shrott 2015-8-19
评论： Walter Roberson 2015-8-19
Today is my first day using Matlab. I have been using C++ for last few years. Could someone please explain why FALSE is printed here?
%%Rounding of decimal fractions
x1=0.3
x2=0.1+0.1 + 0.1
test1=(x1==x2) % PRINTS FALSE? WHY?

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Steven Lord
Steven Lord 2015-8-19
See question 1 in the Mathematics section of the FAQ.
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Image Analyst
Image Analyst 2015-8-19
I suppose for some number combinations it will match all the way out to the umpteenth decimal place and for others it won't. Bottom line: to be robust you need to check non-integer floating point numbers against a tolerance and not for equality.
Walter Roberson
Walter Roberson 2015-8-19
It does not have to be intuitive: it depends upon the exact bit pattern and upon the rounding mode that is in effect.
https://en.wikipedia.org/wiki/Rounding#Round_half_to_even

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