Unum rebuttal

Joseph via Digitalmars-d digitalmars-d at puremagic.com
Fri Sep 15 04:14:24 UTC 2017

On Friday, 15 September 2017 at 03:49:02 UTC, Walter Bright wrote:
> https://people.eecs.berkeley.edu/~wkahan/UnumSORN.pdf
> Prof Kahan, who pretty much invented IEEE 754 floating point 
> arithmetic, debunks unums. Unums pop up now and then with "why 
> don't we support them?"
> The bottom line is there is no magic solution to floating point 
> problems. Unums just trade one set of problems for another.

It's hard to know what's going on when there are mistakes in his 
examples that lead to wrong behavior. How can be be taken 
seriously if his rebuttle has basic mistakes and typos?

page 5:

(y - sqrt(y^2 + 1)) - 1/(y + sqrt(y^2 + 1))

is not zero for all y.

I assume he means

(y - sqrt(y^2 + 1)) + 1/(y + sqrt(y^2 + 1))

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