Re: The disturbing myth of Eiffel portability

[jhd@herold.franken.de (Joachim Durchholz)]

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...

> 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.)

Anybody on his way implementing a FORMULA class for unlimited-precision  
math?

Regards,
-Joachim

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