Re: strings (dollar.cents) into floats

sturlamolden wrote:
On 31 Aug, 02:12, Wildemar Wildenburger
<lasses_w...@xxxxxxxxxxxxxxxxx> wrote:

I've heard (ok, read) that several times now and I understand the
argument. But what use is there for floats, then? When is it OK to use them?

There are fractions that can be exactly represented by floats that
cannot be exactly represented by decimals.

Would you care to give an example?

There are fractions that
can be exactly represented by decimals that cannot be exactly
represented by floats.

Which one is better? Which do we prefer?

What a float cannot do is to represent a decimal fractional number
(e.g. 1.1) exactly. If we need that, we cannot use floats. A notable
example is monetary computations, it covers 99% of the use for decimal
numbers in computers. For this reason, we should never use floats to
add 10 cents to a dollar. The use of decimals for monetary
calculations is mandatory.

That last sentence is patent nonsense, and completely untrue. Many satisfactory financial applications have been written using only floating-point arithmetic. Indeed I believe the accountant's Swiss army knife, the Excel spread***, uses floating-point numbers exclusively.

What you say about floating-point have speed advantages is true, but you go too far in claiming that decimal arithmetic is mandatory for monetary calculations. That's about as sensible as saying that base 12 and base 20 arithmetic units were required to calculate in pounds, shillings and pence.

regards
Steve
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