[FLASH-USERS] #define E problem

[Klaus Weide]

On Mon, 16 Mar 2015, Seyit Hocuk wrote:

> I haven't posted for a while, but I just came accross an interesting problem.
> The interesting part is that I did not have this issue in the past.
> 
> The number of electrons is defined as E (i.e., #define E 4) in Multispecies.h.
> Because of this, wherever I include this header file my exponent notation with
> capital E's are giving wrong numbers. For example 1.0E-24 gives -22.96 (that
> is 1.04 - 24) instead of 10^(-24) , while 1.0e-24 correctly results in the
> right number. If this is the expected behaviour, I find it illogical.

Seyit,

Yes this is ugly...
Something like '#define E 4' should not be in the code, in particular in 
a header file than can get included by arbitrary source files.

Suggestions for you -
1. Only include "Multispecies.h" where it is necessary.
   Avoid capital 'E' in numerical constants in those files.

2. Newer versions of FLASH have kept defining a symbol 'E' for backward
   compatibility, but have changed it to
      #define E (4)
   (note parentheses). This will at least result in a syntax error 
   when 'E' is used in a numerical constant, rather that a quiet 
   corruption of the value as in your case.


> I've succesfully reproduced this with most intel fortran compilers from 11.0
> to 14.0. I don't know why it appears now and did not in the past. The compiler
> flags -uppercase or -lowercase (or -name lowercase) do not help in this case.

I do not expct this behavior to depend on Fortran compiler version.
It could depend on the preprocessor used, but I expect the behavior to be 
the same with different proprocessor implementations. 

> My question is how do I avoid this problem without changing the definition,
> since I would have to change everywhere where the multispecies unit is used
> for electrons, or without manually changing my exponent notations to lower
> cases everywhere. Maybe the manual way isn't much work, but I don't want to
> search the whole code.

See above. 
Using the parenthesised version of the macro may help you find the 
occurrences where you need to change your exponent notation.

Klaus