String representations of numbers and approximate equality

Chris Angelico rosuav at gmail.com
Thu Sep 25 14:46:07 CEST 2014


On Thu, Sep 25, 2014 at 10:40 PM, Dave Angel <davea at davea.name> wrote:
> Another approach is to see if twiddling the last digit gets you
>  from too high to too low. I used this approach to check a trig
>  package I wrote in '75. An answer was close enough if twiddling
>  the last digit changed the result value from too high to too low,
>  or if twiddling the last digit of the argument did. I needed to
>  go both ways because the curve sometimes had a slope greater than
>  one.

Ooh, that sounds clean. So, something like this:

if x * FACTOR > y:
    reduce_last_digit_of_x
    if x * FACTOR > y: error
otherwise do the opposite check

? That's pretty doable.

ChrisA



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