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From: Warren <ve3wwg@gmail.com>
Newsgroups: comp.lang.ada
Subject: Re: Inferring array index type from array object
Date: Tue, 29 Jun 2010 19:31:04 +0000 (UTC)
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John B. Matthews expounded in news:nospam-803846.13501829062010
@news.aioe.org:

> In article <Xns9DA683A562C67WarrensBlatherings@81.169.183.62>,
>  Warren <ve3wwg@gmail.com> wrote:
> 
>> One thing that really irks me (in lack of convenience)
>> is the lack of certain functions in the library support.  
>> For example, I was looking for the inverse of a complex 
>> number function. Did I missed it? My googling didn't 
>> turn up much, nor did grep on the package hdrs.
>> 
>> So because it is missing (AFIK), I had to google it and 
>> figure out how it is done and code it myself.  Wouldn't it
>> be safer if the function was already provided and tested?
>> Wouldn't it also be more accurately coded (floating
>> point can be tricky)? At least it would be tested.
>> 
>> IIRC, I ran into the similar issues with some other
>> functions (ATAN2??). The LOG10() issue was
>> resolved when I discovered there is a base argument
>> in LOG(), so that was just my own "user error".
>> 
>> But even if a function is considered "trivial", I
>> think it would be "safer" to include it. Additionally, 
>> having them provided means that they will 
>> be coded for the best accuracy.
> 
> So, what is the "missing" function?
> 
> <http://www.adaic.com/standards/05rm/html/RM-G-1-2.html>

1) The "inverse" of a complex number. 

2) Also, math libraries usually include atan2(y,x),
since the error can be large with certain ranges
of x in the tan(x) form:

#include <math.h>

double atan2(double y, double x);
float atan2f(float y, float x);
long double atan2l(long double y, long double x);

Warren