Floating point is HARD!

[pne]

Co-worker trying to convince me that "0.5 is not exactly representable in [binary] floating-point".

Hello? It's exactly 2^-1. Of course it's exactly representable!

Maybe you were thinking of 0.1 or something, which isn't representable exactly in binary. But not 0.5.

A little knowledge is a dangerous thing.

Comments

[nik-w.livejournal.com]

0.5 in binary is "0.1", isn't it? Long long time since I did binary fp's, tho, so I could be wrong...

[pne.livejournal.com]

*think briefly*

Yes, it should be. 0.5₁₀ = 2^-1, so yeah, 0.1₂ sounds right.

0.1₁₀, on the other hand, is 0.110011001100…₂—a repeating decimal.

(Hm, I wonder whether this works: 0.1100₂.)

[nik-w.livejournal.com]

I'm astounded that works - LJ normally strips style info out!

[pne.livejournal.com]

Hm? It strips out scripts, but CSS works in entries and comments.

(I think it doesn't work in the bio, though.)

[nik-w.livejournal.com]

Ah - I was going off my experience in trying to get stlye info in the bio. Some use making the pages XHTML compatible if the info put into the bio lets it down because you can't use style tags!

[timwi.livejournal.com]

0.1₁₀, on the other hand, is 0.110011001100…₂—a repeating decimal.

... you mean ... a repeating binary? :-)

[pne.livejournal.com]

Something like that :)