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From: tmcd@tmcd-p4-linux.austin.tx.us (Tim McDaniel)
Newsgroups: comp.lang.java.programmer
Subject: Re: About using assertion
Date: Sat, 21 May 2011 18:37:23 -0500
Organization: Tim McDaniel's home IBM-PC clone running Linux
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In article <se-dnUMuGp0Fj0jQnZ2dnUVZ_o-dnZ2d@earthlink.com>,
Patricia Shanahan  <pats@acm.org> wrote:
>Negative zero is a strange beast. As far as I can tell, it exists
>mainly to produce negative infinity when it is used as a divisor. For
>example, it is equal to zero for comparison purposes.

Hm, I thought it didn't, but the authoritative-looking but old
<http://www.concentric.net/~ttwang/tech/javafloat.htm> says otherwise.

However, Float/Double apparently acts differently from float/double:

    Comparing two Java "Float" objects can have different semantics
    than comparing two Java "float" values. Recall the "float" class
    is a Java primitive class, while java.lang.Float is a subclass of
    "Object".

    A "NaN" value is not equal to itself. However, a "NaN" Java
    "Float" object is equal to itself. The semantic is defined this
    way, because otherwise "NaN" Java "Float" objects cannot be
    retrieved from a hash table.

    (new Float(0.0 / 0.0)).equals(new Float(0.0 / 0.0))  ->  true

    For the class java.lang.Float, objects are ordered from lowest to
    highest: -Infinity, negative numbers, -0.0, 0.0, positive numbers,
    Infinity, NaN. "java.lang.Double" objects are identically ordered.

    (new Float(0.0)).equals(new Float(-0.0))  ->  false

-- 
Tim McDaniel; Reply-To: tmcd@panix.com