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Re: While

From: Paul Pluzhnikov
Subject: Re: While
Date: Sun, 26 Mar 2006 20:32:33 -0800
User-agent: Gnus/5.1006 (Gnus v5.10.6) XEmacs/21.4 (Jumbo Shrimp, linux)

Wilhelm Korrengk <> writes:

> even if I`m not THE Pro coding c++
> I thought I`m already better not to ask the following: 

... code expecting double equality ...

> It does not matter whether i is positive or negative while will
> stop when i is 0.
> But is doesn`t.

You need to read up on float/double representation in the computer:

You should note that 0.1 is *not* representable exactly when using
IEEE-standard representation.

You should *never* compare two floats/doubles for equality.
Instead, always to this:  if (abs(x - y) < epsilon) ...
Or, in the case of your program:

  while (1.e-10 < i) { ... }

Also note that 'i' is ideomatically used as an *integer* index. 
Use 'd' or some descriptive name instead.

In order to understand recursion you must first understand recursion.
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