What will happen to "1 << (-1)" in G++?

[Mr. Ken]

Left shift by negative numbers, will I get 1/2?

Thanks.

[Robert J. Hansen]

Left shift by negative numbers, will I get 1/2?

Why not try it for yourself? The great virtue of computer science is
that in many ways it's an experimental discipline, not a purely
theoretical one.

[Heinz Ozwirk]

"Mr. Ken" <Mr. Ken@asdfschrieb im Newsbeitrag
news:45******** @news.starhub.n et.sg...

Left shift by negative numbers, will I get 1/2?

The result of a shift expression is undefined if its right operand is
negative or greater than or equal to the number of bits used to represent
its left operand.

Heinz

[Mr. Ken]

"Heinz Ozwirk" <ho*****@arcor. dewrote in message
news:45******** **************@ newsspool1.arco r-online.net...

"Mr. Ken" <Mr. Ken@asdfschrieb im Newsbeitrag
news:45******** @news.starhub.n et.sg...

Left shift by negative numbers, will I get 1/2?

The result of a shift expression is undefined if its right operand is
negative or greater than or equal to the number of bits used to represent
its left operand.

Heinz

Thank you.

[Mr. Ken]

"Robert J. Hansen" <ci********@gma il.comwrote in message
news:11******** **************@ b28g2000cwb.goo glegroups.com.. .

Left shift by negative numbers, will I get 1/2?

Why not try it for yourself? The great virtue of computer science is
that in many ways it's an experimental discipline, not a purely
theoretical one.

I received code from other people, but it has the probability of 1 << (-1)..
that's why I asked.

[Nick Keighley]

Robert J. Hansen wrote:

Left shift by negative numbers, will I get 1/2?

Why not try it for yourself? The great virtue of computer science is
that in many ways it's an experimental discipline, not a purely
theoretical one.

this is Really Bad Advice. I you want t to know what a language
construct
is supposed to do then check out a reference. The language standard
itself
is often the best. If you distrust your implementation you may want to
run
a test to verify that your implementation is conforming.

Since "1 << (-1)" has undefined behaviour no amount of empirical
testing
will tell you anything. This weeks test may be invalidated next week by
a
change of platform, compiler version or optimisation settings. In
principal
an implementation could be even worse than that. It may depend on some
obscurity in the hardware.
--
Nick Keighley

Egon: Try to imagine all life as you know it stopping instantaneously
and
every molecule in your body exploding at the speed of light.
Ray: Total protonic reversal....
[DS9000K: Behaviour of Negative Shift]

[Kaz Kylheku]

Mr. Ken wrote:

Left shift by negative numbers, will I get 1/2?

Lame troll.

[Robert J. Hansen]

Why not try it for yourself? The great virtue of computer science is

that in many ways it's an experimental discipline, not a purely
theoretical one.

this is Really Bad Advice.

It is really _good_ advice, given that he specifically asked a question
tied to a specific implementation. If he wants to know what happens in
G++ when this is done, the best way is to try it for yourself. It's
not as if the compiler costs a lot of money to download.

[Robert J. Hansen]

Sometimes a bad advice.

Yes. If he were to be asking "according to the Standard, what happens
when...?", then I would have given him an answer citing the Standard.

But if you're going to ask compiler-specific questions, then "try it
yourself and see" is perfectly reasonable advice. Especially when the
real answer is "it's undefined and the compiler can do anything, and so
the only answer to this question of 'what will G++ do with this?' is
'give it to G++ and see'."

[Clark S. Cox III]

Robert J. Hansen wrote:

>Sometimes a bad advice.

Yes. If he were to be asking "according to the Standard, what happens
when...?", then I would have given him an answer citing the Standard.

But if you're going to ask compiler-specific questions, then "try it
yourself and see" is perfectly reasonable advice. Especially when the
real answer is "it's undefined and the compiler can do anything, and so
the only answer to this question of 'what will G++ do with this?' is
'give it to G++ and see'."

Except that G++ could do it differently each and every time you run the
program.

--
Clark S. Cox III
cl*******@gmail .com