[issue41598] rnd() + rndup() in math

[marco_ocram]

marco_ocram <m.balzaretti at eureka-market.com> added the comment:

i think in your long post you have underlined among others:
1. in binary implementation of floats one bit was reserved to rounding;
2. this one bit is not enough to manage a correct rounding in a converted decimal base;
my considerations:
3. someone i think had evaluated deciding rounding didn't worth more significative digits;
4. the only solution in general can be use more digits to manage rounding in decimal base, not only one but more (i should think better and experiment on how many);
5. the problem in general cannot be solved by an implementation of rounding but from a revision of the implementation of floats (i have solved pretty well my personal need but i'm speaking in general);
6. this is not really a weak impact i think, despite it's not impossible;
7. and last, i think the current implementation could derive from historical reasons when we worked on 8 bits machines, not 64 bits, and one bit was of worth, but i may be wrong.

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<https://bugs.python.org/issue41598>
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