Intended behavior of automatic decimal point (bug 120940)
jralls at ceridwen.us
Thu Jul 27 23:24:11 EDT 2017
> On Jul 27, 2017, at 6:27 PM, Eric Siegerman <pub08-gnc at davor.org> wrote:
> On Thu, Jul 27, 2017 at 08:20:50AM +0000, David T. via gnucash-devel wrote:
>> I think of the decimal placement as applying to the final number in the field
>> (as a sort of edit mask, if you will), rather than a preprocessing function
>> that would apply to every element in an equation.
> I'm not sure that would quite work either.
> Currently, for simple numbers with no arithmetic, "1000" gets
> auto-decimal-pointed ("scaled" hereafter), but "4.50" doesn't,
> which are both just what one wants. The same should apply in
> formulas (I think! -- but more about that at the end). Assuming
> two auto-decimal places, consider:
> 1000 + 4.50
> I (think I) want the first term to get scaled, but not the
> second, giving a result of 14.50.
> OK, so how about we scale each term separately, so that:
> 1000 * 3 + 450 -> 34.50
> but also:
> 1000 * 3 + 4.50 -> 34.50
> ("->" meaning "yields a result of", since "=" just looks wrong
> under the circumstances :-) ).
> But then:
> 10.00 * 3 + 4.50 -> 34.50
> We didn't want to scale the first term after all.
> I've thought of a couple of different approaches:
> - scale each term's resulting value if the term only contains
> 1000*3 + 4000 -> 30 + 40 = 70.00
> 1000*3 + 4000. -> 30 + 4000 = 4030.00
> 1000*3. + 4000 -> 3000 + 40 = 3040.00
> 1000*3. + 4000. -> 3000 + 4000 = 7000.00
> - scale each term's *first* number if it's an integer,
> but never second or subsequent numbers:
> 1000 * 3 -> 30
> 1000 * 3. -> 30
> 1000. * 3 -> 3000
> 1000. * 3. -> 1000
> This is based on the thought that ($20 * $3) is meaningless;
> it only makes sense to multiply money by something that isn't
> But neither of those works in all situations.
> The easiest way out, I think, is to never scale formulas at all,
> only simple numbers. So:
> 4000 -> 40.00 # as currently happens
> 40. -> 40.00 # likewise
> 4000+1 -> 4001.00
> That's how my truly ancient copy of Excel behaves. (I don't
> have access to a modern one.)
> Or perhaps: for formulas, scale the final result (as you say),
> but only if *all* of the numeric values the user typed are
> 1000*3 + 4000 -> 70.00
> 1000*3 + 4000. -> 7000.00
> 1000*3. + 4000 -> 7000.00
> 1000.*3 + 4000 -> 7000.00
> That could boil down to:
> Scale the final result unless the original input string
> contains any "."s (or ","s depending on locale)
> (without even any need to worry whether it's a number or
> a formula).
> But given that it's not entirely clear how even a simple:
> 1000 + 4.50
> should behave, anything with any subtlety at all is going to want
> a fair amount of testing to see whether people actually find it
> usable. So an unsubtle approach like "never scale formulas" is
> probably the safest place to start.
I agree that the only sane way to have auto-decimal is to disable it if the input is a formula. The other sane approach is to remove it completely.
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