Unum rebuttal

[Timon Gehr via Digitalmars-d]

On 16.09.2017 05:32, Joseph wrote:
> On Saturday, 16 September 2017 at 02:27:23 UTC, Timon Gehr wrote:
>> On 15.09.2017 06:14, Joseph wrote:
>>> ... How can be be taken seriously if
>>> his rebuttle has basic mistakes and typos?
>>>
>>
>> :-)
>>
>>> https://people.eecs.berkeley.edu/~wkahan/EndErErs.pdf
>>> page 5:
>>>
>>> (y - sqrt(y^2 + 1)) - 1/(y + sqrt(y^2 + 1))
>>>
>>> is not zero for all y.
>>>
>>> I assume he means
>>> at
>>> (y - sqrt(y^2 + 1)) + 1/(y + sqrt(y^2 + 1))
>>>
>>>
>>
>> No, he means what he wrote, which is
>> |y-√(y²+1)| - 1/(y+√(y²+1)).
>>
>> In D notation:
>> abs(y-sqrt(y^^2+1)) - 1/(y+sqrt(y^^2+1)).
> 
> What are you saying?

I'm saying that there is no mistake in the expression you indicate nor 
in the claims made about it.

> You haven't changed anything but slight notational 
> differences.

The first expression you showed did not take the absolute value of the 
minuend. The second expression you showed also demonstrates rounding 
error, but it is not what he meant to write.

> It's still wrong,

He says the function Q is zero for all positive arguments, which it is.

> so if he really means that then he is 
> wrong, else it's just you.
> 

I'll go as far as to agree that one of the three of us is wrong.
(Or let's make it four; the expression and a slightly weaker version of 
the claim also occur in Gustafson's book.)