[postgis-devel] strange behavoir of LW_ABS

[Mark Cave-Ayland]

nicklas.aven at jordogskog.no wrote:

> Yes, you are right
>  
> But is this what is wanted. Why do we have that macro, is it faster than 
> fabs();
>  
>  From your description Mark I see that putting the -sign outside the 
> parenteses in the macro eliminates this risk:
> #define LW_ABS(a)   ((a) < (0) ? -(a) : (a))
>  
> then it works as I want :-)
>  
> Or is this special behavior wanted and why the macro is there?
>  
> This is no problem now when I have found why (and where) my code broke, 
> but just curious.
>  
> /Nicklas

I'm not sure what the origin of the macro is, so it seems that you've 
found a genuine bug. However, it is likely there because one of the 
platforms supported by PostgreSQL/PostGIS doesn't have fabs() - the 
money is normally on Solaris/Win32 for these types of quirk...


HTH,

Mark.

-- 
Mark Cave-Ayland - Senior Technical Architect
PostgreSQL - PostGIS
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