TOPIC:

Hi,

Current description:
"The logical xor returns the value true if one of its operands is true; it returns the value false if both operands are false or if both operands are true.".

Wouldn't be better to add 'only' in:
"The logical xor returns the value true if only one of its operands is true"?

BR,
Mariusz Kupiec

To make things more precise, I would define it as

The logical xor returns the value true if exactly one of its operands is true"

On the other hand, the existing definition is quite ok already.

And with you xor4b remark, of course you are right: it should return 1 in the latter case.

BR

Stephan

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Original Message

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From: ext Mariusz Kupiec [This email address is being protected from spambots. You need JavaScript enabled to view it.]
Sent: 16. January 2003 19:52
To: This email address is being protected from spambots. You need JavaScript enabled to view it.
Subject: Xor description 15.4


Hi,

Current description:
"The logical xor returns the value true if one of its operands is true; it returns the value false if both operands are false or if both operands are true.".

Wouldn't be better to add 'only' in:
"The logical xor returns the value true if only one of its operands is true"?

BR,
Mariusz Kupiec

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In einer eMail vom 1/16/03 9:56:38 PM W. Europe Standard Time schreibt
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> Hi,

Hi,

It would be simpler, but the current text makes it very explicit and avoids
any possible
mis-understanding as to what the xor function does. The current text
implicitly
tells the user that xor is a binary operation, whereas the simplified text
you propose does
not have this quality.

Cheers,


Claude.


>
> Current description:
> "The logical xor returns the value true if one of its operands is true; it
> returns the value false if both operands are false or if both operands are
> true.".
>
> Wouldn't be better to add 'only' in:
> "The logical xor returns the value true if only one of its operands is true
> "?
>
>

On Thu, 16 Jan 2003, Mariusz Kupiec wrote:

> Hi,
>
> Current description:
> "The logical xor returns the value true if one of its operands is true; it
returns the value false if both operands are false or if both operands are
true.".
>
> Wouldn't be better to add 'only' in:
> "The logical xor returns the value true if only one of its operands is true"?

Both are highly ambiguous.

How about:

The logical xor returns the value true, if its two operands have different
values (i.e. one operand is true and the other one is false), otherwise,
it returns false.

Jacob

In einer eMail vom 1/17/03 2:56:28 PM W. Europe Standard Time schreibt
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Humm,

What do you find ambiguous about the text in the standard?

>
> On Thu, 16 Jan 2003, Mariusz Kupiec wrote:
>
> > Hi,
> >
> > Current description:
> > "The logical xor returns the value true if one of its operands is true;
> it returns the value false if both operands are false or if both operands
> are true.".
> >
> > Wouldn't be better to add 'only' in:
> > "The logical xor returns the value true if only one of its operands is
> true"?
>
> Both are highly ambiguous.
>
> How about:
>
> The logical xor returns the value true, if its two operands have different
> values (i.e. one operand is true and the other one is false), otherwise,
> it returns false.
>
> Jacob
>

Cheers,

Claude.

Claude Desroches e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.
Technical Architect This email address is being protected from spambots. You need JavaScript enabled to view it.
Strategic Test Solutions Ltd.
City Gate East.
Toll House Hill,
Nottingham.
NG1 5FS.

Tel: +44 115 958 6600
Fax: +44 115 958 6633
Mob: +44 796 648 2165

On Fri, 17 Jan 2003, Claude Desroches wrote:

> In einer eMail vom 1/17/03 2:56:28 PM W. Europe Standard Time schreibt
> This email address is being protected from spambots. You need JavaScript enabled to view it.:
>
> Humm,
>
> What do you find ambiguous about the text in the standard?
>
> >
> > On Thu, 16 Jan 2003, Mariusz Kupiec wrote:
> >
> > > Hi,
> > >
> > > Current description:
> > > "The logical xor returns the value true if one of its operands is true;
> > it returns the value false if both operands are false or if both operands
> > are true.".

Mathematically speaking, the sentence describe this:

a xor true = true
true xor a = true
false xor false = false
true xor true = false
undefined xor false = undefined
false xor undefined = undefined
undefined xor undefined = undefined

As there is nowhere said that the expression 'a' (i.e. one operand)
cannot be undefined (as is the case for some other logical operators),
this is clearly not the intended interpretation, although it is
a consistent one with the text.

Actually, a very strict person could even say that the above definition
is contradictory, as for a = true, 'a xor true' as well as 'true xor a'
is true AND false simultaneously.

Of course, you can argue that nobody could MEAN this by the above
definition, but that's not how definitions work. They alone should
make the meaning clear without any contradictions.

> > > Wouldn't be better to add 'only' in:
> > > "The logical xor returns the value true if only one of its operands is
> > true"?

Here, I thought that the second sentence was to be removed, leaving the
same room for interpretation regarding the strictness of the operation.

> > Both are highly ambiguous.
> >
> > How about:
> >
> > The logical xor returns the value true, if its two operands have different
> > values (i.e. one operand is true and the other one is false), otherwise,
> > it returns false.

Yes, here somebody could say what about the value 'undefined'.
But an undefined expressions is normally one which has no value,
so this doesn't apply here - at least for the first case.

The best way to describe logical operators is probably tables :-)

Jacob

In einer eMail vom 1/17/03 5:42:46 PM W. Europe Standard Time schreibt
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Hi Jacob,

Isn't mathematics wonderful! :-). Clear, concise, unambiguous!


> The best way to describe logical operators is probably tables :-)
>
This might be overkill, but it would definitely spell things out clearly as
to
what the result of performing a given operation on one or more operands (as
required)
of a given operator.

Cheers,


Claude.


Claude Desroches e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.
Technical Architect This email address is being protected from spambots. You need JavaScript enabled to view it.
Strategic Test Solutions Ltd.
City Gate East.
Toll House Hill,
Nottingham.
NG1 5FS.

Tel: +44 115 958 6600
Fax: +44 115 958 6633
Mob: +44 796 648 2165