Re: The disturbing myth of Eiffel portability

[fred@genesis.demon.co.uk (Lawrence Kirby)]

In article <6LW663dk3RB@herold.franken.de>
           jhd@herold.franken.de "Joachim Durchholz" writes:

>fred@genesis.demon.co.uk wrote 24.11.96:
>
>> Financial calculations within (fairly generous) limits can use IEEE
>> floating point and be *proven* correct barring bugs in the implementation.
>> But bugs can affect integer calculations as well.
>
>However, integer bugs are less likely. After all, IEEE format is much more  
>complicated (at least in comparison to two's-complement integer). For IEEE  
>format, there is room for interpretation (really there isn't, but some  
>implementors behave as if there were).
>E.g. the infamous Pentium bug was in the FPU, not in the ALU. Of course  
>this is jumping to conclusions from a statistically insignificant  
>sample...

Doesn't the Pentium use the FPU for integer division?

>> No
>> format can represent general irrational quantities precisely.
>
>There is one - storing formulae instead of quantities :)
>
>Actually this is feasible - Mathematica and Co. do exactly this. This  
>allows them to compute as many digits as required on the fly, without loss  
>of precision from intermediate results.
>(Of course there is still a round-off error, but it is always on the last  
>printed digits.)

So Mathematica still have to evaluate the formulae at some point when you
need a value and the issue of how you round is still there.

-- 
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Lawrence Kirby | fred@genesis.demon.co.uk
Wilts, England | 70734.126@compuserve.com
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