libitl-0.6.4 :A possible BUG? C# porting almost complete!

["Meor Ridzuan Meor Yahaya" <meor dot ridzuan at gmail dot com>]

Dear All,

I was working on porting libitl to C# to make it run on .net platform
. Right now I'm almost done with prayertime . I'll be working on hijri
date converter later.

During my work, I've found a possible bug. In astro.h, it has the
following definition:

#define DEG_TO_RAD(A) (A * (PI/180.0))


Then in astro.c, it uses it as follows (in getRefraction function):

part2 = 1 / tan(DEG_TO_RAD(sunAlt + (7.31/(sunAlt + 4.4)))) + 0.0013515;

Since in C# there is no such thing as #define, I created a function as follows:

double DEG_TO_RAD(double A){ return A*(PI/180);}

However, the above statement for part2 yields different values. I've
tried so many things to trace what is the problem. First, I compiles
the sample program using Microsoft C++ toolkit (free compiler from MS,
version 2003).  I thought that it might be a compiler bug. Then I
downloaded gcc, ( Dev-C++ distribution), I got the same results as MS
compiler. Finally I came to conclusion the the problematic statement
is the following:

DEG_TO_RAD(sunAlt + (7.31/(sunAlt + 4.4)))

Since libitl uses #define statement, I think it has a side effects.
Then , I tried 2 different approaches:
1. rearrage the statement to the following:
temp=sunAlt + (7.31/(sunAlt + 4.4));
DEG_TO_RAD(temp);

2. Convert the DEG_TO_RAD to a proper function.

In both instances, I got the same results as my C# program. So, my
conclusion is, the bug arises because of the use of #define statement.
We can evaluate the statement properly by doing the following:
DEG_TO_RAD(sunAlt + (7.31/(sunAlt + 4.4)))=
( sunAlt + (7.31/(sunAlt + 4.4))* (PI/180.0)),  => this how #define
works, and how compiler replaces the statement, which, obviously shows
that it is not the same as the above approaches.

The whole thing causes time for Maghrib and Shurooq to be earlier a
few minutes than my version. Since I'm not the author of this program
and don't know much on how the calculation works, I hope others can
check this out. Hope the auther can verify this, whether this is a
real bug of intended to be like that. if this is a true bug, then my
suggestion is to convert the #define statement into a real function,
so that we don't get any surprises anymore.

Lastly, if anyone want to give my port to C# a try , please let me
know. I'll send to the library. The porting was done almost with
minimal changes on the program layout, just to make it work.  Later
I'll probably make more changes to make it more Object Oriented and
more tailored to C# environment. (the porting was done in 2 days, btw)

Wassalam.