OpenEuphoria

Re: BUG! Erratic for loop behavior

• Posted by Rolf Schröder <r.schr at t-online.de> Mar 23, 2002
• 460 views

Andy Serpa wrote:
> ...
> ------------------------------
> for i = 31.1 to 34.2 by .1 do
>   ? i
> end for
> ------------------------------
> stops at 34.1 (!), NOT as expected.
> 
Hi Andy,

that's ok. Look at this:

    for i = 31.1 to 34.1 by 0.1 do
        printf(1,"%20.15f\n",i)
    end for

and you will notice why: the decimal given value 0.1 is exactly
representable in the computer for it has to stores it internally as an
binary value with a limited number of bits. Actually, 0.1 (dec.) is has
an unlimited binary representation: 0.0001100110011..... . This is the
correct way to do it (have in mind that 31.1 and 34.1 are also not
exactly representable!):

    for i = 311 to 341 by 1 do
        printf(1,"%20.15f\n",i/10)
    end for

Have a nice day, Rolf