Re: Significance of using + before function calls.

Re: Significance of using + before function calls.

[Steve Graegert]

On 3/15/06, Vamsi <krishna.vamsi@wipro.com> wrote:
> Hi List,
>
> i have seen a code snippet which starts with + symbol,
>
> +system("ls -l");
>
> what is the significance of using + symbol before system.
>
> i also tried using + before printf ,, like +printf("Some text"); and it
> is compiling and working tooo,,
>
> Can somebody clarify wht does that + signify??

The unary plus operator returns the value of an expression.  Neither
the unary plus nor unary minus operators produce lvalues and is of
limited use.

	\Steve

Re: Significance of using + before function calls.

[Per Jessen]

Steve Graegert wrote:
> 
> The unary plus operator returns the value of an expression.  Neither
> the unary plus nor unary minus operators produce lvalues and is of
> limited use.

So what might be the intention of someone using it like the OP
described?  It doesn't make much sense, right?




Per Jessen

Re: Significance of using + before function calls.

[Joel M. Pareja]

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The placement of '+' or '-' before the function call is performing a
unary operator on the return value of the function.

Vamsi wrote:
> Hi List,
> 
> i have seen a code snippet which starts with + symbol,
> 
> +system("ls -l");
> 
> what is the significance of using + symbol before system.
> 
> i also tried using + before printf ,, like +printf("Some text"); and it 
> is compiling and working tooo,,
> 
> Can somebody clarify wht does that + signify??
> 
> Thank You.
> 
> -Vamsi
> 
> -
> To unsubscribe from this list: send the line "unsubscribe 
> linux-c-programming" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html

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Re: Significance of using + before function calls.

[Joel M. Pareja]

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That must be a typographical error.

Because '+' does nothing to the return value of the function.
Also because there is no lvalue in the expression.

But with '-', there is an effect.


int dummy_func() { return 5; }

int num = -dummy_func();


As a result, num will be '-5'.

Vamsi wrote:
> 
> Joel M. Pareja wrote:
> 
>> The placement of '+' or '-' before the function call is performing a
>> unary operator on the return value of the function.
> 
> does it server any purpose ? , unary '+'  operator will not have any 
> significance effect on the return value
> 
> -Vamsi
> 
>>
>> Vamsi wrote:
>>
>>> Hi List,
>>>
>>> i have seen a code snippet which starts with + symbol,
>>>
>>> +system("ls -l");
>>>
>>> what is the significance of using + symbol before system.
>>>
>>> i also tried using + before printf ,, like +printf("Some text"); and 
>>> it is compiling and working tooo,,
>>>
>>> Can somebody clarify wht does that + signify??
>>>
>>> Thank You.
>>>
>>> -Vamsi
>>>
>>> -
>>> To unsubscribe from this list: send the line "unsubscribe 
>>> linux-c-programming" in
>>> the body of a message to majordomo@vger.kernel.org
>>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>>
> 
> -
> To unsubscribe from this list: send the line "unsubscribe 
> linux-c-programming" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html

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Re: Significance of using + before function calls.

[Glynn Clements]

Vamsi wrote:

> i have seen a code snippet which starts with + symbol,
> 
> +system("ls -l");

I suspect that the "code snippet" in question comes from the output of
"diff -u", and the + is part of the diff syntax, not part of the code.

-- 
Glynn Clements <glynn@gclements.plus.com>

Re: Significance of using + before function calls.

[Steve Graegert]

On 3/15/06, Per Jessen <per@computer.org> wrote:
> Steve Graegert wrote:
> >
> > The unary plus operator returns the value of an expression.  Neither
> > the unary plus nor unary minus operators produce lvalues and is of
> > limited use.
>
> So what might be the intention of someone using it like the OP
> described?  It doesn't make much sense, right?

I suppose it's there for a clean implementation of operators in C. 
While the unary minus returns the negative of the operand the unary
plus returns the value to avoid ambiguity, i.e. shall the unary plus
return the positive of a negative operand, as the unary minus does? 
IMHO, not a result I'd expect.

	\Steve

Significance of using + before function calls.

[Vamsi]

Hi List,

i have seen a code snippet which starts with + symbol,

+system("ls -l");

what is the significance of using + symbol before system.

i also tried using + before printf ,, like +printf("Some text"); and it 
is compiling and working tooo,,

Can somebody clarify wht does that + signify??

Thank You.

-Vamsi

Re: Significance of using + before function calls.

[Vamsi]

Joel M. Pareja wrote:

> The placement of '+' or '-' before the function call is performing a
> unary operator on the return value of the function.

does it server any purpose ? , unary '+'  operator will not have any 
significance effect on the return value

-Vamsi

>
> Vamsi wrote:
>
>> Hi List,
>>
>> i have seen a code snippet which starts with + symbol,
>>
>> +system("ls -l");
>>
>> what is the significance of using + symbol before system.
>>
>> i also tried using + before printf ,, like +printf("Some text"); and 
>> it is compiling and working tooo,,
>>
>> Can somebody clarify wht does that + signify??
>>
>> Thank You.
>>
>> -Vamsi
>>
>> -
>> To unsubscribe from this list: send the line "unsubscribe 
>> linux-c-programming" in
>> the body of a message to majordomo@vger.kernel.org
>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>

Re: Significance of using + before function calls.

[Vamsi]

Glynn Clements wrote:

>Vamsi wrote:
>
>  
>
>>i have seen a code snippet which starts with + symbol,
>>
>>+system("ls -l");
>>    
>>
>
>I suspect that the "code snippet" in question comes from the output of
>"diff -u", and the + is part of the diff syntax, not part of the code.
>
>  
>
No, i verified it is not a patch, or the output of diff.

Thank You.

Re: Significance of using + before function calls.

[Tomas Janousek]

Hello,

Vamsi napsal(a):
> Can somebody clarify wht does that + signify??

It suppresses the warning about ignored returned value returned by 
splint, for example.

-- 
.---------    Tomáš Janoušek   a.k.a. Liskni_si    ---------.
: NOMI team, developer, http://tomi.nomi.cz/   tomi@nomi.cz :
' JID:liskni_si@jabber.cz, ICQ#161807083, tel:+420608876277 '

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