From: Tammo Freese <tammo.freese@...>
Date: 2001-03-06T19:36:59+09:00
Subject: [ruby-talk:12112] NaN, Infinity (Bug?)


After the Pickaxe Book, first print, p. 320
a = -1.0        -> -1.0
a.nan?          -> false
a = Math.log(a) -> NaN
a.nan?          -> true

But testing (ruby 1.6.2 (2000-12-18) [i386-cygwin])

#
a = -1.0
puts a
puts a.nan?
a = Math.log(-1.0)
puts a
puts a.nan?
#

gives 

-1.0
false
-Infinity
false

This issue was already raised in ruby-talk #5085 by Mathieu Bouchard.

However, as the results of the code in the pickaxe book are generated
by running the code (aren't they?), 1.6.0 seems to have the correct(?)
behaviour (returning NaN).

Is this a defect or an error in the pickaxe book?

 

-
Tammo Freese
freese@acm.org