Avoiding float and double in monetary calculation

[wane]

Hello,
I have heard that one should avoid using float and double in monetary
calculation because of the lack of preciseness.
What is a good alternative?

Thanks

[Malcolm]

"Rouben Rostamian" <ro****@pc18.ma th.umbc.edu> wrote in message

When dealing with Bill Gates' bank account, use an arbitrary precision
arithmetic library. Search the web for GNU MP library, but don't
tell Bill it's GNU.

This leads to the serious point that you could always have hyper-inflation,
which means that a program handling monetary values is likely to break
unless it uses arbitrary-precision integers.

[Mike Wahler]

Keith Thompson <ks*@cts.com> wrote in message
news:ye******** *****@king.cts. com...

Morris Dovey <mr*****@iedu.c om> writes:
[...]

Again, it depends on the range of values. For a program on my machine
to keep track of my checking account, a char should be sufficient to
handle the full range in pennies ($1.27 through -$1.28).

ITYM " ... through -$1.27" Some implementations allow -128
in a signed char, but it's not required.

-Mike

[Morris Dovey]

Mike Wahler wrote:

Keith Thompson <ks*@cts.com> wrote in message
news:ye******** *****@king.cts. com...

Morris Dovey <mr*****@iedu.c om> writes:
[...]

Again, it depends on the range of values. For a program on my machine
to keep track of my checking account, a char should be sufficient to
handle the full range in pennies ($1.27 through -$1.28).

ITYM " ... through -$1.27" Some implementations allow -128
in a signed char, but it's not required.

I guess that means that I'll just have to be more careful about
the checks I write (or start using my thumbs in personal
financial calculations [thus far I've reserved my thumbs as carry
and overflow bits] - I've considered using one thumb as sign and
the other as a ninth [high order] magnitude bit; but I'm not
certain that I actually have a need for the additional capacity -
and I have serious misgivings about undetected under-/overflow
conditions...
--
Morris Dovey
West Des Moines, Iowa USA
C links at http://www.iedu.com/c

[Morris Dovey]

John L Fjellstad wrote:

Morris Dovey wrote:

Question for you: What is the 1/100 part of a Euro called?

Cent.

Thanks. Should be easy (even for me) to remember.
--
Morris Dovey
West Des Moines, Iowa USA
C links at http://www.iedu.com/c

[Mark McIntyre]

On Wed, 20 Aug 2003 22:08:40 -0400, in comp.lang.c , wane
<no****@intechs .net> wrote:

Hello,
I have heard that one should avoid using float and double in monetary
calculation because of the lack of preciseness.
This is certainly a viewpoint. For what its worth, I work in
investment banking, and we find doubles quite adequate even for large
scale financial transactions. In over a decade in the buisness I have
come across only a couple of instances where it actually mattered.
What is a good alternative?

If you want perfect precision, use integer types, and a scaling factor
to turn back into pennies. Note that this can limit your range unless
you use special big number handling routines. The assets of many a
company, converted into say Turkish Lira, would overflow most builtin
types. It may also be slower, esp if you have to use a special
library.

--
Mark McIntyre
CLC FAQ <http://www.eskimo.com/~scs/C-faq/top.html>
CLC readme: <http://www.angelfire.c om/ms3/bchambless0/welcome_to_clc. html>
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