extraction operator

[Taras_96]

Hi all,

Jesse Liberty writes:

"cin.get() >>myVarOne >myVarTwo; // illegal

The return value of (cin.get() >myVarOne) is an integer, not an
iostream object."

(http://newdata.box.sk/bx/c/htm/ch16.htm)

I would think that that the reason why this wouldn't work is because
cin.get() returns an int, not because (cin.get() >mVarOne) is an
integer...

Anyone agree?

Taras

[sk_usenet]

Re: extraction operator


"Taras_96" <taras.di@gmail .comwrote in message

Hi all,
>
Jesse Liberty writes:
>
"cin.get() >>myVarOne >myVarTwo; // illegal
>
The return value of (cin.get() >myVarOne) is an integer, not an
iostream object."
>
(http://newdata.box.sk/bx/c/htm/ch16.htm)
>
I would think that that the reason why this wouldn't work is because
cin.get() returns an int, not because (cin.get() >mVarOne) is an
integer...
Anyone agree?

If mVarOne is an integral type then (cin.get() >mVarOne) would return an
integer. The code won't even compile if mVarOne has any other type.

--

http://techytalk.googlepages.com

[acehreli@gmail.com]

Re: extraction operator

On Apr 30, 6:21 am, Taras_96 <taras...@gmail .comwrote:

Hi all,
>
Jesse Liberty writes:
>
"cin.get() >>myVarOne >myVarTwo; // illegal
>
The return value of (cin.get() >myVarOne) is an integer, not an
iostream object."

The author probably means that "it will not work the way one might
expect." It is illegal only if myVarOne or myVarTwo is uninitialized.
(I don't remember whether the values must be less than or equal to the
total bits in 'int'.)

cin.get() >myVarOne

is the result of an int shifted right by the value of myVarOne

/* ... */ >myVarTwo

is further shifting the result of the previous operation right some
more.

>
(http://newdata.box.sk/bx/c/htm/ch16.htm)
>
I would think that that the reason why this wouldn't work is because
cin.get() returns an int, not because (cin.get() >mVarOne) is an
integer...

The code should compile and work in that possibly unexpected way.

Ali

[sk_usenet]

Re: extraction operator

<acehreli@gmail .comwrote in message

On Apr 30, 6:21 am, Taras_96 <taras...@gmail .comwrote:

>Hi all,
>>
>Jesse Liberty writes:
>>
>"cin.get() >>myVarOne >myVarTwo; // illegal
>>
>The return value of (cin.get() >myVarOne) is an integer, not an
>iostream object."

>
The author probably means that "it will not work the way one might
expect." It is illegal only if myVarOne or myVarTwo is uninitialized.
(I don't remember whether the values must be less than or equal to the
total bits in 'int'.)

I think (after looking at the link provided by OP) probably the author means
that this code won't work the way "cin >mVar1 >mVar2" would have worked.

<Quote from link>
When you write cin >VarOne >varTwo >varThree;, the first extraction is
evaluated (cin >VarOne). The return value from this is another istream
object, and that object's extraction operator gets the variable varTwo. It
is as if you had written this: ((cin >varOne) >varTwo) >varThree;
</Quote from link>

--

http://techytalk.googlepages.com

[James Kanze]

Re: extraction operator

On Apr 30, 3:21 pm, Taras_96 <taras...@gmail .comwrote:

Jesse Liberty writes:

"cin.get() >>myVarOne >myVarTwo; // illegal

The return value of (cin.get() >myVarOne) is an integer, not
an iostream object."

(http://newdata.box.sk/bx/c/htm/ch16.htm)

I would think that that the reason why this wouldn't work is
because cin.get() returns an int, not because (cin.get() >>
mVarOne) is an integer...

Anyone agree?

As others have pointed out, 1) it's not illegal (since myVarOne
and myVarTwo have type char), but 2) it almost certainly doesn't
mean what you want.

I might add in general that, having taken a quick look at the
page, it seems full of errors. I didn't read it in detail, but
of the four or five sentences I did notice, about have were
wrong. I don't think I'd recommend this text.

--
James Kanze (GABI Software) email:james.kan ze@gmail.com
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[Taras_96]

Re: extraction operator

Thanks everyone - I didn't even think of the shift operator :)

Taras