CODEWITHSUNDEEP
javadouble
TJ Jaksa
TJ Jaksa

Reputation: 31

Java double precision math

I'm doing a bit of modding to a popular game (Minecraft) and I seen these lines in the terrain generation,

double d4 = 1.0D;
d4 *= d4; 
d4 *= d4;
d4 = 1.0D - d4;
double d5 = (noise1[l1] + 256D) / 512D;
d5 *= d4;

I was wondering what the point of d4 was, because on the fourth line it would always be 0, wouldn't it?

Upvotes: 3

Views: 853

Answers (1)

Jon Skeet
Jon Skeet

Reputation: 1500515

Yes, in straight Java at least this would be guaranteed to be 0.

For all the inaccuracies of floating binary point arithmetic, 1.0 itself can be represented exactly, and the result of multiplying it by itself will always get back to simply 1.0.

Are you sure there's nothing else going on elsewhere to make it slightly different to 1.0d? Or perhaps it was historically some value other than 0.1?

Upvotes: 5

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