How to subtract two close numbers?
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Hi!
I've compiled the code below and i don't know why it doesn't give exact zero.
I'll appreciate if someone helps me.
format long
x=5.4;
y=x-5;
z=y-0.4;
disp(z)
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Stephen23
le 16 Oct 2019
Modifié(e) : Stephen23
le 16 Oct 2019
"..i don't know why it doesn't give exact zero."
The decimal values 5.4 and 0.4 cannot be represented exactly using binary floating point numbers, in just the same way that you cannot write 1/3 using a finite decimal fraction.
Use num2strexact see the precise decimal values of the closest floating point binary numbers:
The behaviors of floating point numbers are quite well documented, you need to learn how to write your code taking them into account. Start by reading these:
etc.etc.
This is worth reading as well:
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