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dartfloating-pointdoublefloating-accuracy

Dart - Subtracting some double values gives wrong result

I have picked two random double numbers:

double a = 7918.52;
double b = 5000.00;

I would expect to get 2918.52 from a - b.
Well, it gives me a result of 2918.5200000000004, which seems odd.

print(a - b); // -> 2918.5200000000004

But if I change double a to 7918.54, I will get the expected result of 2918.54.

Can someone explain to me why some double values result in unexpected rounding issues and others do not?

Solution

  • The reason for this is floating-point arithmetic and the fact that Dart uses the IEEE 754 standard as far as I am concerned.

    This happens for all languages that use floating-point arithmetic. You can read through similar questions regarding other programming languages.

    General question about floating-point arithmetic in modern programming languages.