[fpc-devel] Floating point precision

[Colin Western]

Jonas Maebe wrote:
> 
> On 09 Apr 2007, at 22:38, Colin Western wrote:
> 
> 
>> Having said that, for numerical programming if double is wanted, the 
>> evaluation as double in the absence of specific precision information 
>> is actually desirable, and avoids some hard to find errors. Values 
>> like Sqrt(2) are common, which I should presumably write as 
>> Sqrt(Double(2)) to be sure I don't loose precision. It came up because 
>> my application (which requires double rather than single accuracy) was 
>> giving slightly different results for different architectures. I have 
>> now gone through and fixed the differences I can find, and the results 
>> are now the same, but it is difficult to be sure I have caught all the 
>> problem areas.
>>
>> Is there some way of optionally making double the default for 
>> constants (rather than single) as a way of avoiding these errors?
> 
> Please file a bug report/feature request for this. The current behaviour 
> is needed for Delphi compatibility, and for avoiding wrong precision 
> loss warnings like in
>   http://www.freepascal.org/mantis/view.php?id=7179
> 
I have filed the feature request at
<http://www.freepascal.org/mantis/view.php?id=8678>

Having looked at 7179 would the behavior I want be obtained if we had 
the option just to treat 1.0 as Double rather than Single?

Colin