Re: How PostgreSQL's floating-point hurts everyone everywhere

Peter Eisentraut wrote:
>
> peter=# select 1.0/0.0;
> ERROR:  float8div: divide by zero error
>
> Division by zero is not an "error" in floating point arithmetic.
   No?
   Oh, then 7 = 5 because:
       Assuming              2a = b                         | * 2                             4a = 2b
    | + 10a                            14a = 10a + 2b                  | - 7b                       14a - 7b = 10a - 5b
                | ()                     7 (2a - b) = 5 (2a - b)                | / (2a - b)
 7 = 5
 
   In  the  given  context,  you  should find the mistake pretty   easy.  Maybe the message should be changed to
       ERROR:  floatdiv: divide by zero nonsense                                        ^^^^^^^^
   because a division by zero results in nonsense? Or should  it   just  return a random value? What is the result of a
division  by  zero?   It's  definitely  not  infinity,  as  the   above   demonstrates!
 
   You  might  be looking from a managers PoV.  Managers usually   use this kind of arithmetic to choose salaries.  Any
engineer  knows that
 
       work = power * time
   We all know that time is money and that power is knowlede. So
       work = knowledge * money
   and thus
                 work       money = ---------               knowledge
   Obviously, the lesser you  know,  the  more  money  you  get,   independant  of  the  work  to  be  done. As soon as
youknow   nothing (zero), any money you get for the work is nonsense!
 
   This applies well to the real world, so it makes  sense  from   an OO PoV.  But in science, I think it's still an
error.
   Since  PostgreSQL  is an ORDBMS (not an OODBMS), I think it's   correct to report an error instead of returning some
random.
 
   :-)


Jan

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