Why does the following code print 0?
#include<cstdio>
int main()
{
float a = 0.1;
printf("%d", int(2 - a * a * 100));
return 0;
}
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lkdx2
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9Does this answer your question? [Is floating point math broken?](https://stackoverflow.com/questions/588004/is-floating-point-math-broken) – Passerby Jan 24 '22 at 12:41
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20.1 is periodic in binary, so cannot represented exactly as float, instead it is rounded – and obviously in your case slightly larger than 0.1, resulting in (0.1 + e) * (0.1 + e) * 100, giving a result slightly larger than 1, thus the difference is slightly smaller than 1, thus converted to 0. – Aconcagua Jan 24 '22 at 12:45
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1Conclusion: If you rely on *exact* math floating point is a rather bad choice... – Aconcagua Jan 24 '22 at 12:47