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math.h correction for atan2 in 2nd quadrant

 
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Kurt Franke
Guest







math.h correction for atan2 in 2nd quadrant
PostPosted: Tue Dec 17, 2002 2:00 pm     Reply with quote

in math.h, the results for atan2 calls that are in the 2nd
quadrant are false. In the second quadrant the return should
be:

return (PI-atan(z));

here's the snippet of code from math.h. Changes are in lines
632, 633 for my version.

I told ccs about this before, but they seem only to have added
the correct line as a comment..

-Kurt


--
z=y/x;
switch(quad)
{
case 1:
{
return atan(z);
break;
}
case 2:
{
// return (atan(z)+PI_DIV_BY_TWO);
return (PI-atan(z)); // correction
break;
}
case 3:
{
return (atan(z)-PI);
break;
}
case 4:
{
return (-atan(z));
break;
}
}
___________________________
This message was ported from CCS's old forum
Original Post ID: 10101
Hans Wedemeyer
Guest







Re: math.h correction for atan2 in 2nd quadrant
PostPosted: Tue Dec 17, 2002 10:15 pm     Reply with quote

That's strange ! I don't have any code like that in math.h
Which version are you using ?

I ame using V3.129
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This message was ported from CCS's old forum
Original Post ID: 10108
Kurt Franke
Guest







Re: math.h correction for atan2 in 2nd quadrant
PostPosted: Wed Dec 18, 2002 8:08 am     Reply with quote

:=That's strange ! I don't have any code like that in math.h
:=Which version are you using ?
:=
:=I ame using V3.129

3.129 here also. That is strange. Maybe the installer didn't
remove the old file on my system??

-Kurt
___________________________
This message was ported from CCS's old forum
Original Post ID: 10116
PCM programmer



Joined: 06 Sep 2003
Posts: 20137

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Re: math.h correction for atan2 in 2nd quadrant
PostPosted: Wed Dec 18, 2002 1:47 pm     Reply with quote

:=:=That's strange ! I don't have any code like that in math.h
:=:=Which version are you using ?
:=:=
:=:=I ame using V3.129
:=
:=3.129 here also. That is strange. Maybe the installer didn't
:=remove the old file on my system??
---------------------------------------------------------

It's in there. I deleted math.h and re-installed PCM vs. 3.129.
In the atan2 function, at line 630, it has this code:

<PRE>
case 2:
{
return (atan(z)+PI_DIV_BY_TWO);
// return (PI-atan(z));
break;
}
</PRE>

Hans uses PCH. Maybe PCH has a different version of math.h ?
___________________________
This message was ported from CCS's old forum
Original Post ID: 10125
Hans Wedemeyer
Guest







What's going on ?
PostPosted: Thu Dec 19, 2002 3:46 pm     Reply with quote

:=Hans uses PCH. Maybe PCH has a different version of math.h

Almost correct, I use PCWH which includes all compilers.

Doing a search for math.h, I found an old example under pcw, which is where PCWH cames from, and there I found the atan2() that you have talked about !

In the help it mentions Ex_Tank.c as an example for atan2(),
when I load Ex_Tank.c I don't see a direct call to atan2() ! but, I get an error for pwr() function call!

I checked the include setup in the IDE and it does not point to the old PCW ....

This is strange !
When I get time I will clean out the CCS installations and start again !
___________________________
This message was ported from CCS's old forum
Original Post ID: 10149
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