OpenEuphoria

Re: ESL - math.e - rounding

• Posted by Jason Gade <jaygade at yahoo.com> Aug 03, 2005
• 766 views

Juergen Luethje wrote:
> 
> Hi all,
> 
> here are some thoughts concerning ESL rounding functions.
> 
> Any function for rounding a number should take a second argument that
> denotes the number of digital places that we want the result to have,
> e.g.
>     round(77.123456, 3) = 77.123
> 
> There is an IEEE standard for rounding. A *different* way of rounding
> is what we call in German "kaufmaennisches Runden".
> Translated word by word to English, this would be "commercial rounding".
> Does this (or a similar) term exist in English?
>      round_half_even(x,n)     -- according to IEEE
>      round_half_up(x,n)       -- "kaufmaennisches Runden"
> 
> 
> Both functions sometimes return different results, when the (n+1)th
> decimal place of x equals 5:
>      round_half_even()        -- rounds to nearest even value
>      round_half_up()          -- always rounds up  ( surprise!  )
> 
> -- Example
> x = 7.125
> round_half_even(x,2)    -->  7.12
> round_half_up(x,2)      -->  7.13
> 
> x = 7.135
> round_half_even(x,2)    -->  7.14
> round_half_up(x,2)      -->  7.14
> 
> 
> What do you all think?
> 
> Regards,
>    Juergen
> 
> -- 
> Have you read a good program lately?
> 
> 

Not being a memember of the IEEE standards committee, round_half_up() would be
the behavior I expect from a rounding function. That was the way I was always
taught to round.

Except, how does it work for negative numbers? Does it round towards + or -?


Alexander Toresson wrote:
> round_half_up() would be roof() in qb.
> There's also a function called floor() in qb, which always rounds down.

It would be nice to have different words for this. For one Euphoria already has
a floor() function, for two it sounds like I'm building a house instead of a
program.

Just like peek() and poke() make me feel like a pervert.

How about
round_up(num, places)
round_down(num, places)
round_even(num, places)

Also, how do these functions work on numbers with very large exponents? Such as
7.135e15? Are they only for numbers within 15 significant figures of 0?

=====================================
Too many freaks, not enough circuses.

j.