From: Wesley J Landaker <wjl@...>
Date: 2003-12-14T00:54:26+09:00
Subject: Re: types? casting and bools

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On Saturday 13 December 2003 8:37 am, KONTRA Gergely wrote:
> On 1213, Austin Ziegler wrote:
> > On Sat, 13 Dec 2003 01:56:18 +0900, KONTRA Gergely wrote:
> > > Why ruby handle booleans so liberally?
> >
> > It doesn't. Ruby treats all values excepting false and nil as true.
> > It sounds like you're wanting 0 to be treated as false.
>
> No, I'm just asking how ruby "dare" to convert my 0 to true (or
> false, it is the same).

Outside of any programming language, an abstract boolean has only two=20
values: true, and false.=20

Many programming languages map true to non-zero and false to zero, but=20
that isn't necessary a given. Return values for commands in a shell are=20
the opposite, 0 is true, anything non-zero is false. Even in languages=20
like C, technically 0 means true and non-zero means false, but it's=20
semantically exactly the opposite for 99.9% of all standard functions,=20
which return 0 for true, and non-zero for false.

Some languages, like Python or Perl, have a big list of what is false,=20
and everything else is true. Sometimes it's hard to know what is going=20
to be true or false in those languages unless you are very familiar=20
with the nuances.

In digital logic design, often 0 means false, and 1 means true. Except=20
if you're talking about shared bus architectures, then almost always 0=20
means true, 0 means false.

While it works for certain domains, it's probably not a good idea in=20
general to assume that integers map have any intrinsic mapping to=20
booleans: it's always a characteristic of the language or problem=20
domain in question.

In ruby, it's very simple and straightforward. Only two things are=20
logically false: nil, and false. There isn't any "conversion" going on,=20
it's an intrinsic part of the language. There is no "Boolean" data type=20
that things are being "converted" to; *everything* is true, *except*=20
nil and false.=20

=2D-=20
Wesley J. Landaker - wjl@icecavern.net
OpenPGP FP: 4135 2A3B 4726 ACC5 9094  0097 F0A9 8A4C 4CD6 E3D2


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