[fpc-pascal] round(2.5)=2

[Bernd Oppolzer]

Am 08.06.2018 um 14:47 schrieb Klaus Hartnegg:
> Hi,
>
> The round function behaves different than in TurboPascal, and its 
> English Wiki page differs from the German page.
>
> When given an argument halfway between to integers, FreePascal rounds 
> to the nearest even number, TurboPascal always rounds up (except when 
> it is set to mode $N+, but default is $N-).
>
> The German Wiki pages for Round and SetSoundMode (URLs below) contain 
> a warning to not use SetRoundMode, because that also affects internal 
> calculations, and how numbers are stored in variables when they do not 
> fit with full precision.
>
> How serious is this issue compared with using a different rounding 
> method?
>
> The german pages suggest to use this function instead:
> function round(x: Float): Integer;  { requires unit math for 'float' }
> begin
>   if x > 0 then
>       round := trunc(x + 0.5)
>   else
>       round := -trunc(-x + 0.5);
> end;
>
> That is fine, except that I will likely forget it in some unit, and 
> manually inspecting all units is less reliable than when the compiler 
> ensures it.
>

This is not sufficient, IMO, when using float,
look here:

http://bernd-oppolzer.de/job9i032.htm

> In Turbo-Pascal the browsing feature (search,symbol) of the IDE can 
> show a list of all places where system.round gets called. The 
> FreePascal IDE does not show that list (see my other email).
>
> Is there some other reliable(!) way to fix or check this? Maybe a map 
> file with all functions that got linked into the executable?
>
> The Wiki pages are
> - wiki.freepascal.org/Round
> - wiki.freepascal.org/Round/de
> - wiki.freepascal.org/SetRoundMode
> - wiki.freepascal.org/SetRoundMode/de
>
> If the warning is correct, there should also be a note on
> https://www.freepascal.org/docs-html/rtl/math/setroundmode.html
>
> thanks,
> Klaus
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