gnu software bugs - long double

[David Given]

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On 02/11/13 19:48, Mischa Baars wrote:
[...]
> I have written a couple of new trigonometric functions for use in
> the library, and actually I need this to function properly.

The point is that 1.1 simply cannot be represented precisely as a IEEE
floating point number, for precisely the same reasons that 1/3 cannot
be represented precisely as a decimal number (1.3333...). This is
intrinsic to the way that floating point numbers work. If you try,
you'll get the closest number that IEEE floats *can* represent.

If you really need a completely precise representation of 1.1, then
you're not going to be able to use IEEE floats --- you'll have to use
decimals or some sort of fractional representation instead. I don't
know if gcc can help you with those, but there are endless helper
libraries that will do both for you. They're usually pretty slow, though.

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