* how to implement this ?
@ 2013-01-07 14:31 horseriver
2013-01-07 14:53 ` Andrew Haley
0 siblings, 1 reply; 11+ messages in thread
From: horseriver @ 2013-01-07 14:31 UTC (permalink / raw)
To: gcc-help
hi:
how to implement this assignment by MACRO?
int a,b,c ;
((a==0)?b:c)=8;
if use this sentence ,gcc will tell :error: lvalue required as left operand of assignment
is there s implementation for this with macro define?
is there suggestion ?
thanks!
^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: how to implement this ?
2013-01-07 14:31 how to implement this ? horseriver
@ 2013-01-07 14:53 ` Andrew Haley
2013-01-07 15:09 ` horseriver
0 siblings, 1 reply; 11+ messages in thread
From: Andrew Haley @ 2013-01-07 14:53 UTC (permalink / raw)
To: horseriver; +Cc: gcc-help
On 01/07/2013 04:46 AM, horseriver wrote:
> hi:
>
> how to implement this assignment by MACRO?
> int a,b,c ;
>
> ((a==0)?b:c)=8;
This is for help with GCC, not general C coding help.
*((a==0) ? &b : &c) = 8;
But this is really horrible code. I wouldn't do it.
Andrew.
^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: how to implement this ?
2013-01-07 14:53 ` Andrew Haley
@ 2013-01-07 15:09 ` horseriver
2013-01-07 15:21 ` Andrew Haley
0 siblings, 1 reply; 11+ messages in thread
From: horseriver @ 2013-01-07 15:09 UTC (permalink / raw)
To: Andrew Haley; +Cc: gcc-help
On Mon, Jan 07, 2013 at 02:31:19PM +0000, Andrew Haley wrote:
> On 01/07/2013 04:46 AM, horseriver wrote:
> > hi:
> >
> > how to implement this assignment by MACRO?
> > int a,b,c ;
> >
> > ((a==0)?b:c)=8;
>
> This is for help with GCC, not general C coding help.
>
> *((a==0) ? &b : &c) = 8;
>
> But this is really horrible code. I wouldn't do it.
thans!
why gcc report that error ?
gcc can translate " ((a==0)?b:c)=8 " into if-else sentence .
wht is the reason ï¼
>
> Andrew.
>
^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: how to implement this ?
2013-01-07 15:09 ` horseriver
@ 2013-01-07 15:21 ` Andrew Haley
2013-01-07 15:25 ` horseriver
0 siblings, 1 reply; 11+ messages in thread
From: Andrew Haley @ 2013-01-07 15:21 UTC (permalink / raw)
To: horseriver; +Cc: gcc-help
On 01/07/2013 05:11 AM, horseriver wrote:
> On Mon, Jan 07, 2013 at 02:31:19PM +0000, Andrew Haley wrote:
>> On 01/07/2013 04:46 AM, horseriver wrote:
>>> hi:
>>>
>>> how to implement this assignment by MACRO?
>>> int a,b,c ;
>>>
>>> ((a==0)?b:c)=8;
>>
>> This is for help with GCC, not general C coding help.
>>
>> *((a==0) ? &b : &c) = 8;
>>
>> But this is really horrible code. I wouldn't do it.
>
> thans!
>
> why gcc report that error ?
>
> gcc can translate " ((a==0)?b:c)=8 " into if-else sentence .
>
> wht is the reason ï¼
Please supply the test case and the error message.
Andrew.
^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: how to implement this ?
2013-01-07 15:21 ` Andrew Haley
@ 2013-01-07 15:25 ` horseriver
2013-01-07 15:35 ` Andrew Haley
0 siblings, 1 reply; 11+ messages in thread
From: horseriver @ 2013-01-07 15:25 UTC (permalink / raw)
To: Andrew Haley; +Cc: gcc-help
On Mon, Jan 07, 2013 at 03:09:31PM +0000, Andrew Haley wrote:
> On 01/07/2013 05:11 AM, horseriver wrote:
> > On Mon, Jan 07, 2013 at 02:31:19PM +0000, Andrew Haley wrote:
> >> On 01/07/2013 04:46 AM, horseriver wrote:
> >>> hi:
> >>>
> >>> how to implement this assignment by MACRO?
> >>> int a,b,c ;
> >>>
> >>> ((a==0)?b:c)=8;
> >>
> >> This is for help with GCC, not general C coding help.
> >>
> >> *((a==0) ? &b : &c) = 8;
> >>
> >> But this is really horrible code. I wouldn't do it.
> >
> > thans!
> >
> > why gcc report that error ?
> >
> > gcc can translate " ((a==0)?b:c)=8 " into if-else sentence .
> >
> > wht is the reason ï¼
>
> Please supply the test case and the error message.
>
ok
here is this code :
#define INPUT_KEYCODE(dev, scancode) ((dev->keycodesize == 1) ? ((u8*)dev->keycode)[scancode] : \
((dev->keycodesize == 2) ? ((u16*)dev->keycode)[scancode] : (((u32*)dev->keycode)[scancode])))
and here is the callee code :
unsigned int keycode ;
INPUT_KEYCODE(dev, scancode) = keycode;
dev is a struct , scancode is a unsigned int
and gcc report error is :
error: lvalue required as left operand of assignment
thanks!
> Andrew.
>
>
^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: how to implement this ?
2013-01-07 15:25 ` horseriver
@ 2013-01-07 15:35 ` Andrew Haley
2013-01-07 15:44 ` horseriver
0 siblings, 1 reply; 11+ messages in thread
From: Andrew Haley @ 2013-01-07 15:35 UTC (permalink / raw)
To: horseriver; +Cc: gcc-help
On 01/07/2013 05:39 AM, horseriver wrote:
> On Mon, Jan 07, 2013 at 03:09:31PM +0000, Andrew Haley wrote:
>> On 01/07/2013 05:11 AM, horseriver wrote:
>>> On Mon, Jan 07, 2013 at 02:31:19PM +0000, Andrew Haley wrote:
>>>> On 01/07/2013 04:46 AM, horseriver wrote:
>>>>> hi:
>>>>>
>>>>> how to implement this assignment by MACRO?
>>>>> int a,b,c ;
>>>>>
>>>>> ((a==0)?b:c)=8;
>>>>
>>>> This is for help with GCC, not general C coding help.
>>>>
>>>> *((a==0) ? &b : &c) = 8;
>>>>
>>>> But this is really horrible code. I wouldn't do it.
>>>
>>> thans!
>>>
>>> why gcc report that error ?
>>>
>>> gcc can translate " ((a==0)?b:c)=8 " into if-else sentence .
>>>
>>> wht is the reason ï¼
>>
>> Please supply the test case and the error message.
>>
>
> ok
>
> here is this code :
>
> #define INPUT_KEYCODE(dev, scancode) ((dev->keycodesize == 1) ? ((u8*)dev->keycode)[scancode] : \
> ((dev->keycodesize == 2) ? ((u16*)dev->keycode)[scancode] : (((u32*)dev->keycode)[scancode])))
>
> and here is the callee code :
>
> unsigned int keycode ;
>
> INPUT_KEYCODE(dev, scancode) = keycode;
>
> dev is a struct , scancode is a unsigned int
>
> and gcc report error is :
>
> error: lvalue required as left operand of assignment
That is the wrong error.
I need to see the whole of the code that resulted in the error that was
"gcc can translate " ((a==0)?b:c)=8 " into if-else sentence ."
^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: how to implement this ?
2013-01-07 15:35 ` Andrew Haley
@ 2013-01-07 15:44 ` horseriver
2013-01-07 15:49 ` Andrew Haley
0 siblings, 1 reply; 11+ messages in thread
From: horseriver @ 2013-01-07 15:44 UTC (permalink / raw)
To: Andrew Haley; +Cc: gcc-help
On Mon, Jan 07, 2013 at 03:29:59PM +0000, Andrew Haley wrote:
> On 01/07/2013 05:39 AM, horseriver wrote:
> > On Mon, Jan 07, 2013 at 03:09:31PM +0000, Andrew Haley wrote:
> >> On 01/07/2013 05:11 AM, horseriver wrote:
> >>> On Mon, Jan 07, 2013 at 02:31:19PM +0000, Andrew Haley wrote:
> >>>> On 01/07/2013 04:46 AM, horseriver wrote:
> >>>>> hi:
> >>>>>
> >>>>> how to implement this assignment by MACRO?
> >>>>> int a,b,c ;
> >>>>>
> >>>>> ((a==0)?b:c)=8;
> >>>>
> >>>> This is for help with GCC, not general C coding help.
> >>>>
> >>>> *((a==0) ? &b : &c) = 8;
> >>>>
> >>>> But this is really horrible code. I wouldn't do it.
> >>>
> >>> thans!
> >>>
> >>> why gcc report that error ?
> >>>
> >>> gcc can translate " ((a==0)?b:c)=8 " into if-else sentence .
> >>>
> >>> wht is the reason ï¼
> >>
> >> Please supply the test case and the error message.
> >>
> >
> > ok
> >
> > here is this code :
> >
> > #define INPUT_KEYCODE(dev, scancode) ((dev->keycodesize == 1) ? ((u8*)dev->keycode)[scancode] : \
> > ((dev->keycodesize == 2) ? ((u16*)dev->keycode)[scancode] : (((u32*)dev->keycode)[scancode])))
> >
> > and here is the callee code :
> >
> > unsigned int keycode ;
> >
> > INPUT_KEYCODE(dev, scancode) = keycode;
> >
> > dev is a struct , scancode is a unsigned int
> >
> > and gcc report error is :
> >
> > error: lvalue required as left operand of assignment
>
> That is the wrong error.
>
> I need to see the whole of the code that resulted in the error that was
> "gcc can translate " ((a==0)?b:c)=8 " into if-else sentence ."
gcc can translate " ((a==0)?b:c)=8 " into if-else sentence
is my idea ,not a reported error
thanks!
>
^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: how to implement this ?
2013-01-07 15:44 ` horseriver
@ 2013-01-07 15:49 ` Andrew Haley
2013-01-07 15:52 ` horseriver
0 siblings, 1 reply; 11+ messages in thread
From: Andrew Haley @ 2013-01-07 15:49 UTC (permalink / raw)
To: horseriver; +Cc: gcc-help
On 01/07/2013 05:57 AM, horseriver wrote:
> gcc can translate " ((a==0)?b:c)=8 " into if-else sentence
>
> is my idea ,not a reported error
Oh, you mean why does C not allow ((a==0)?b:c)=8;
You'd have to ask the C standard committee. It's not something
that the language allows.
Andrew.
^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: how to implement this ?
2013-01-07 15:49 ` Andrew Haley
@ 2013-01-07 15:52 ` horseriver
2013-01-07 17:05 ` Andrew Haley
0 siblings, 1 reply; 11+ messages in thread
From: horseriver @ 2013-01-07 15:52 UTC (permalink / raw)
To: Andrew Haley; +Cc: gcc-help
On Mon, Jan 07, 2013 at 03:44:01PM +0000, Andrew Haley wrote:
> On 01/07/2013 05:57 AM, horseriver wrote:
> > gcc can translate " ((a==0)?b:c)=8 " into if-else sentence
> >
> > is my idea ,not a reported error
>
> Oh, you mean why does C not allow ((a==0)?b:c)=8;
>
> You'd have to ask the C standard committee. It's not something
> that the language allows.
but I find this use in kernel code .
code have been post in last mail
>
> Andrew.
>
^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: how to implement this ?
2013-01-07 15:52 ` horseriver
@ 2013-01-07 17:05 ` Andrew Haley
0 siblings, 0 replies; 11+ messages in thread
From: Andrew Haley @ 2013-01-07 17:05 UTC (permalink / raw)
To: horseriver; +Cc: gcc-help
On 01/07/2013 06:07 AM, horseriver wrote:
> On Mon, Jan 07, 2013 at 03:44:01PM +0000, Andrew Haley wrote:
>> On 01/07/2013 05:57 AM, horseriver wrote:
>>> gcc can translate " ((a==0)?b:c)=8 " into if-else sentence
>>>
>>> is my idea ,not a reported error
>>
>> Oh, you mean why does C not allow ((a==0)?b:c)=8;
>>
>> You'd have to ask the C standard committee. It's not something
>> that the language allows.
> but I find this use in kernel code .
GCC used to allow it as a language extension, a long time ago.
Andrew.
^ permalink raw reply [flat|nested] 11+ messages in thread
* Re:how to implement this ?
@ 2013-01-07 15:30 ugiwgh
2013-01-07 15:39 ` how " horseriver
0 siblings, 1 reply; 11+ messages in thread
From: ugiwgh @ 2013-01-07 15:30 UTC (permalink / raw)
To: horseriver; +Cc: gcc-help
If I didn't understand wrong, you can do it like this.
#define calc(_a,_b,_c) ((0==(_a))?((_b)==8):((_c)=8))
------------------ Original ------------------
From: "horseriver"<horserivers@gmail.com>;
Date: Mon, Jan 7, 2013 12:46 PM
To: "gcc-help"<gcc-help@gcc.gnu.org>;
Subject: how to implement this ?
hi:
how to implement this assignment by MACRO?
int a,b,c ;
((a==0)?b:c)=8;
if use this sentence ,gcc will tell :error: lvalue required as left operand of assignment
is there s implementation for this with macro define?
is there suggestion ?
thanks!
^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: how to implement this ?
2013-01-07 15:30 ugiwgh
@ 2013-01-07 15:39 ` horseriver
0 siblings, 0 replies; 11+ messages in thread
From: horseriver @ 2013-01-07 15:39 UTC (permalink / raw)
To: ugiwgh; +Cc: gcc-help
On Mon, Jan 07, 2013 at 11:25:10PM +0800, ugiwgh wrote:
> If I didn't understand wrong, you can do it like this.
>
> #define calc(_a,_b,_c) ((0==(_a))?((_b)==8):((_c)=8))
>
actually,I want use ((a==0)?b:c) to select a variable name ,which can be used as left value also as right value.
thanks!
gcc-help <gcc-help@gcc.gnu.org>
>
>
> ------------------ Original ------------------
> From: "horseriver"<horserivers@gmail.com>;
> Date: Mon, Jan 7, 2013 12:46 PM
> To: "gcc-help"<gcc-help@gcc.gnu.org>;
>
> Subject: how to implement this ?
>
>
>
> hi:
>
> how to implement this assignment by MACRO?
> int a,b,c ;
>
> ((a==0)?b:c)=8;
>
> if use this sentence ,gcc will tell :error: lvalue required as left operand of assignment
>
> is there s implementation for this with macro define?
>
> is there suggestion ?
>
>
> thanks!
^ permalink raw reply [flat|nested] 11+ messages in thread
end of thread, other threads:[~2013-01-07 15:52 UTC | newest]
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2013-01-07 14:31 how to implement this ? horseriver
2013-01-07 14:53 ` Andrew Haley
2013-01-07 15:09 ` horseriver
2013-01-07 15:21 ` Andrew Haley
2013-01-07 15:25 ` horseriver
2013-01-07 15:35 ` Andrew Haley
2013-01-07 15:44 ` horseriver
2013-01-07 15:49 ` Andrew Haley
2013-01-07 15:52 ` horseriver
2013-01-07 17:05 ` Andrew Haley
2013-01-07 15:30 ugiwgh
2013-01-07 15:39 ` how " horseriver
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