1. Re: Whats the problem in this function?<decoded from the
Subject: Re: Whats the problem in this function?<decoded from the
mime(mostly???)>
To: EUPHORIA at cwisserver1.mcs.muohio.edu
Steve Lee wrote:
>
> -- I made the function that returns the rounded-up,down,off(is it right=
expression? my english
> -- is somhow poor :) value on the given digit.
> -- but when used in the main program, i got a problem on calculating
Round-Down process.
> -- an example blelow.
>
> global constant ROUND_UP =3D 1, --=BF=C3=B8=B2
> ROUND_DOWN =3D 0, --=B3=BB=B8=B2
> ROUND_OFF =3D 0.5 --=B9=DD=BF=C3=B8=B2
>
> global function round_number(atom flag, object number, integer digit)
> -- flag : =BF=C3=B8=B2,=B3=BB=B8=B2,=B9=DD=BF=C3=B8=B2=C0=BB =B0=E1=C1=A4=
> -- number : =B0=E8=BB=EA=C7=D2 =BC=FD=C0=DA
> -- digit : =B9=DD=BF=C3=B8=B2(=BF=C3=B8=B2,=B3=BB=B8=B2)=C7=D2 =C0=DA=B8=
=AE=BC=F6(=BC=D2=BC=F6=C1=A1 =C0=CC=C7=CF=B4=C2 - =B7=CE =C7=A5=BD=C3; -2=
->
=BC=D2=BC=F6=C1=A1=C0=CC=C7=CF 2
> -- =C2=B0=C0=DA=B8=AE) ; 0=C0=BA =B5=C9 =BC=F6 =BE=F8=C0=BD, =C0=D4=
=B7=C2=C7=CF=B8=E9 "There's no digit 0!"=B8=A6 =B9=DD=C8=AF
>
> object answer
>
> if digit =3D 0 then answer =3D "There's no digit 0!"
> elsif digit < 0 then
> answer =3D floor(number/power(10,digit+1)+flag)*power(10,digit+1)
> elsif digit > 0 then
> answer =3D floor(number/power(10,digit)+flag)*power(10,digit)
> end if
> return answer
> end function
>
> atom number
> object value
>
> number =3D 1648.174
>
> for i =3D 2 to -6 by -1 do
> value =3D round_number(ROUND_DOWN,number,i)
> if i =3D 0 then
> puts(1,value&'\n')
> else
> printf(1,"%4.5f rounded down by digit %d into %4.5f
\n",{number,i,value})
> end if
> end for
>
> -- now result below
>
> --1648.17400 rounded down by digit 2 into 1600.00000
> --1648.17400 rounded down by digit 1 into 1640.00000
> --There's no digit 0!
> --1648.17400 rounded down by digit -1 into 1648.00000
> --1648.17400 rounded down by digit -2 into 1648.10000
> --1648.17400 rounded down by digit -3 into 1648.17000
> --1648.17400 rounded down by digit -4 into 1648.17300 -> problem starts=
to occur!! expecting
> -- 1648.17400!!
> --1648.17400 rounded down by digit -5 into 1648.17390
> --1648.17400 rounded down by digit -6 into 1648.17399
>
> -- I know many other excellent routines for this job but i still want t=
o
know WHAT IS THE
> -- PROBLEM IN MY ALGORITHM!!
>
> -- Steve.
>
Steve,
I haven=B4t studied your code thoroughly, but I think there is nothing wr=
ong
with it, the problem that arises has to do with the way Euphoria stores
numbers internally.
I=B4m struggling with this rounding problem myself for quite some time no=
w.
I=B4m not the one to explain this in detail to you, if I could maybe that=
would have solved half the problem already.
In short, if BCD - Binary Coded Digits - are used to represent numbers,
than calculation to a greater precision can be accomplished, but at the
expense of speed.
Robert Craig has chosen for speed, which is right in 99% of all cases.
If someone could please look at a possibility to implement this in
Euphoria, I for one would be very glad. Or maybe this is something for
Gnuphoria and-or Petephoria.
To understand what is going on internally in your rounding program, try
printing out some in-between results, or better still, use the trace
facility.
I hope this subject will find some interest amongst other
non-game-programming Euphorians. In the past, I have gotten some answers =
on
BCD programming, but the sources were in assembler, too difficult for me.=
But if there is some one.....
Regards,
Ad Rienks
