Machine precision

[Ron Natalie]

Acording to Knuth "it is an abuse of terminology to call the fraction
part a mantissa, since that term has quite a different meaning in
connection with logarithms".

Lots of words have different meanings in different contexts.
Knuth's no paragon of linguistic sanity. He can't even get typography right.

 

[Ron Natalie]

But it is not pedantic. Misappropriating and misusing a word from another
field can be disastrous, as it is in this case.

Show me how this is disasterous. It's not just a case of me "stealing the word."
It was done long before I got to it. It's no different than dozens of other terms
in a new science like computers.

You show me a hundred
programmers and I will show you a significant number who think it really
*IS* a mantissa as in logarithms.

Give me a break. I doubt that. Frankly, most programmers these days
have no clue what a mantissa means with respect to logarithms at all.
Those of us old farts remember using log charts where you'd have to
seperate the whole and fractional parts of the logarithm, but those went
the way of the dodo 25 years ago when the inexpensive scientific calculator
came out. My log charts and my slide rule haven't seen the light of day in
decades.

Those who know what a logaritm mantissa don't have to think to hard to realize
it just means the fractional part of the value, as opposed to athe fractional part of
the exponent.

 

[osmium]

Acording to Knuth "it is an abuse of terminology to call the fraction
part a mantissa, since that term has quite a different meaning in
connection with logarithms".

But this is getting a bit pedantic...

But it is not pedantic. Misappropriating and misusing a word from another
field can be disastrous, as it is in this case. You show me a hundred
programmers and I will show you a significant number who think it really
*IS* a mantissa as in logarithms. Which is the very reason for this
sub-thread.

 

[osmium]

Show me how this is disasterous. It's not just a case of me "stealing the word."
It was done long before I got to it. It's no different than dozens of other terms
in a new science like computers.


Give me a break. I doubt that. Frankly, most programmers these days
have no clue what a mantissa means with respect to logarithms at all.
Those of us old farts remember using log charts where you'd have to
seperate the whole and fractional parts of the logarithm, but those went
the way of the dodo 25 years ago when the inexpensive scientific calculator
came out. My log charts and my slide rule haven't seen the light of day in
decades.

Those who know what a logaritm mantissa don't have to think to hard to realize
it just means the fractional part of the value, as opposed to athe fractional part of
the exponent.

Your post is there. Res ipsa loquitur.

 

[Philipp]

Thank you all for your answers.
The proposed article "What every computer scientist should know about
floating-point arithmetic" is definitely worth reading.

I'm using gcc 3.3 or Metrowerks compiler and am surprised that sizeof(int) =
sizeof(long) = 4 (I thought long was bigger than int) and that sizeof(long
double) = 12 (with gcc), and sizeof(long double) = 8 (with Metrowerks) are
different... Hmm need to use some caution when doing precise calculation
then...

Anyway that's not the point here Best regards
Phil