[GRASS5] r.flow: strange compile error M_PI

[Paul Kelly]

On Tue, 28 Jun 2005, Brad Douglas wrote:

> On Tue, 2005-06-28 at 23:38 +1200, Hamish wrote:
>>> Personally, I would just conditionalise the local definitions, e.g.:
>>>
>>> 	#ifndef M_PI
>>> 	#define M_PI 3.14159265358979323846
>>> 	#endif
>>
>> why not go straight to the long?
>>
>> 3.1415926535897932384626433832795029
>> or
>> 3.1415926535897932384626433832795029L
>>
>> (but don't call that M_PI)
>
> That should be called M_PIl.
>
> I like the idea of adding these macros to gis.h, if not sorting it out
> with autoconf (still my favored method).

I think the logic with autoconf should be to use it if it simplifies 
things; in this case it appears to make it more complicated so the simple 
solution is better. Unless it is possibel for the definition of M_PI in math.h 
to be somehow "better" than our own version. It actually probably makes the 
output of GRASS more consistent cross-platform if every module is always 
using the same definition (in gis.h), rather than perhaps that or perhaps 
the one in math.h, depending on compiler options and platform-specific 
stuff.

Just my impression,

Paul