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Sorry for interrupt,because my mother language is not English,it may be a little confused to read the c programming language.

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  Sorry for interrupt,because my mother language is not English,it may be a little confused to read the c programming language. Zhang Yuan <zhabgyuan1993@gmail.com> - 2012-06-11 23:47 -0700
    Re: Sorry for interrupt,because my mother language is not English,it may be a little confused to read the c programming language. Ike Naar <ike@iceland.freeshell.org> - 2012-06-12 08:04 +0000
      Re: Sorry for interrupt,because my mother language is not English,it may be a little confused to read the c programming language. Zhang Yuan <zhabgyuan1993@gmail.com> - 2012-06-12 08:26 -0700
      Re: Sorry for interrupt,because my mother language is not English,it may be a little confused to read the c programming language. jgk@panix.com (Joe keane) - 2012-06-13 21:07 +0000
        Re: Sorry for interrupt,because my mother language is not English,it may be a little confused to read the c programming language. Ike Naar <ike@iceland.freeshell.org> - 2012-06-14 04:35 +0000
    Re: Sorry for interrupt,because my mother language is not English,it may be a little confused to read the c programming language. Barry Schwarz <schwarzb@dqel.com> - 2012-06-12 08:45 -0700
      Re: Sorry for interrupt,because my mother language is not English,it may be a little confused to read the c programming language. Zhang Yuan <zhabgyuan1993@gmail.com> - 2012-06-12 08:51 -0700

#22141 — Sorry for interrupt,because my mother language is not English,it may be a little confused to read the c programming language.

charpter6
6.1 basic

"The tag names this kind of structure, and can be used subsequently as a shorthand for the part of the 
declaration in braces. "

I don't understand it well.
I refer to some native language(Chinese) translated from English.
just literal translation.

Will you put up an example for me to understand it?
Thank you.
Forgive me for my silly request.

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#22144

On 2012-06-12, Zhang Yuan <zhabgyuan1993@gmail.com> wrote:
> charpter6
> 6.1 basic
>
> "The tag names this kind of structure, and can be used subsequently
> as a shorthand for the part of the 
> declaration in braces. "
>
> I don't understand it well.
> I refer to some native language(Chinese) translated from English.
> just literal translation.
>
> Will you put up an example for me to understand it?

They probably mean that with this type definition:

  struct S { int i; double d; };

the declaration

  struct S x;

can be seen as a shorthand for

  struct { int i; double d; } x;

Indeed, both declarations will declare a variable x that is
a struct type with an int member i and a double member d.

But there are subtle differences. For instance, with

  struct S x;
  struct S y;

x and y have the same type, and can be assigned to each other, like in

  x = y;

but with

  struct S x;
  struct { int i; double d; } y;

x and y have different types, and cannot be assigned to each other:

  x = y;

is not allowed.

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#22163

On Tuesday, June 12, 2012 4:04:11 PM UTC+8, Ike Naar wrote:
> On 2012-06-12, Zhang Yuan <zhabgyuan1993@gmail.com> wrote:
> > charpter6
> > 6.1 basic
> >
> > "The tag names this kind of structure, and can be used subsequently
> > as a shorthand for the part of the 
> > declaration in braces. "
> >
> > I don't understand it well.
> > I refer to some native language(Chinese) translated from English.
> > just literal translation.
> >
> > Will you put up an example for me to understand it?
> 
> They probably mean that with this type definition:
> 
>   struct S { int i; double d; };
> 
> the declaration
> 
>   struct S x;
> 
> can be seen as a shorthand for
> 
>   struct { int i; double d; } x;
> 
> Indeed, both declarations will declare a variable x that is
> a struct type with an int member i and a double member d.
> 
> But there are subtle differences. For instance, with
> 
>   struct S x;
>   struct S y;
> 
> x and y have the same type, and can be assigned to each other, like in
> 
>   x = y;
> 
> but with
> 
>   struct S x;
>   struct { int i; double d; } y;
> 
> x and y have different types, and cannot be assigned to each other:
> 
>   x = y;
> 
> is not allowed.


Thank you.Learn a lot.

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#22222

In article <slrn3vfsjtdtvr.o50.ike@iceland.freeshell.org>,
Ike Naar  <ike@iceland.freeshell.org> wrote:
>They probably mean that with this type definition:
>
>  struct S { int i; double d; };
>
>the declaration
>
>  struct S x;
>
>can be seen as a shorthand for
>
>  struct { int i; double d; } x;

No, it's just wrong.

A struct defined with a tag can be referred to by the same tag, and then
it's the same type; it's probably illegal to redefine it with the same
tag, even if the member types and names are identical, and a struct with
a tag will never be the same type as an anonymous struct, and neither
will two anonymous structs be the same type.

So that's part of the problem he's having.

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#22246

On 2012-06-13, Joe keane <jgk@panix.com> wrote:
> In article <slrn3vfsjtdtvr.o50.ike@iceland.freeshell.org>,
> Ike Naar  <ike@iceland.freeshell.org> wrote:
>>They probably mean that with this type definition:
>>
>>  struct S { int i; double d; };
>>
>>the declaration
>>
>>  struct S x;
>>
>>can be seen as a shorthand for
>>
>>  struct { int i; double d; } x;
>
> No, it's just wrong.
>
> A struct defined with a tag can be referred to by the same tag, and then
> it's the same type; it's probably illegal to redefine it with the same
> tag, even if the member types and names are identical, and a struct with
> a tag will never be the same type as an anonymous struct, and neither
> will two anonymous structs be the same type.

We are in agreement.
You more or less restate what was stated
in the part of my post that you snipped.

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#22166

On Mon, 11 Jun 2012 23:47:42 -0700 (PDT), Zhang Yuan
<zhabgyuan1993@gmail.com> wrote:

>charpter6
>6.1 basic
>
>"The tag names this kind of structure, and can be used subsequently as a shorthand for the part of the 
>declaration in braces. "
>
>I don't understand it well.
>I refer to some native language(Chinese) translated from English.
>just literal translation.
>
>Will you put up an example for me to understand it?
>Thank you.
>Forgive me for my silly request.

This is from K&R II, page 128.

The example they use is 
     struct point {int x; int y;};

In this case, the tag is the token "point" (without the quotes).

I think the idea they are trying to explain is that if you want to
define an object of this type, you can use
     struct point p;
and if later you need to define another object of this type you can
use
     struct point q;

Compare this with what happens if the structure type has no tag, as in
     struct {int x; int y;};

In this case, to define an object of this type you would need
     struct {int x; int y;} p;
and for a second object
     struct {int x; int y;} q;

If the structure type has many members, this can be quite tiresome. It
also becomes difficult to verify that both p and q are the same type.

So the tag "point" serves as a shorter way to specify 
"{int x; int y;}".  This shorthand is available only for types that
have tags (unions, structures, and enums).

-- 
Remove del for email

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#22167

Thank you.
I understand it well now
 

On Tuesday, June 12, 2012 11:45:48 PM UTC+8, Barry Schwarz wrote:
> On Mon, 11 Jun 2012 23:47:42 -0700 (PDT), Zhang Yuan
> <zhabgyuan1993@gmail.com> wrote:
> 
> >charpter6
> >6.1 basic
> >
> >"The tag names this kind of structure, and can be used subsequently as a shorthand for the part of the 
> >declaration in braces. "
> >
> >I don't understand it well.
> >I refer to some native language(Chinese) translated from English.
> >just literal translation.
> >
> >Will you put up an example for me to understand it?
> >Thank you.
> >Forgive me for my silly request.
> 
> This is from K&R II, page 128.
> 
> The example they use is 
>      struct point {int x; int y;};
> 
> In this case, the tag is the token "point" (without the quotes).
> 
> I think the idea they are trying to explain is that if you want to
> define an object of this type, you can use
>      struct point p;
> and if later you need to define another object of this type you can
> use
>      struct point q;
> 
> Compare this with what happens if the structure type has no tag, as in
>      struct {int x; int y;};
> 
> In this case, to define an object of this type you would need
>      struct {int x; int y;} p;
> and for a second object
>      struct {int x; int y;} q;
> 
> If the structure type has many members, this can be quite tiresome. It
> also becomes difficult to verify that both p and q are the same type.
> 
> So the tag "point" serves as a shorter way to specify 
> "{int x; int y;}".  This shorthand is available only for types that
> have tags (unions, structures, and enums).
> 
> -- 
> Remove del for email



On Tuesday, June 12, 2012 11:45:48 PM UTC+8, Barry Schwarz wrote:
> On Mon, 11 Jun 2012 23:47:42 -0700 (PDT), Zhang Yuan
> <zhabgyuan1993@gmail.com> wrote:
> 
> >charpter6
> >6.1 basic
> >
> >"The tag names this kind of structure, and can be used subsequently as a shorthand for the part of the 
> >declaration in braces. "
> >
> >I don't understand it well.
> >I refer to some native language(Chinese) translated from English.
> >just literal translation.
> >
> >Will you put up an example for me to understand it?
> >Thank you.
> >Forgive me for my silly request.
> 
> This is from K&R II, page 128.
> 
> The example they use is 
>      struct point {int x; int y;};
> 
> In this case, the tag is the token "point" (without the quotes).
> 
> I think the idea they are trying to explain is that if you want to
> define an object of this type, you can use
>      struct point p;
> and if later you need to define another object of this type you can
> use
>      struct point q;
> 
> Compare this with what happens if the structure type has no tag, as in
>      struct {int x; int y;};
> 
> In this case, to define an object of this type you would need
>      struct {int x; int y;} p;
> and for a second object
>      struct {int x; int y;} q;
> 
> If the structure type has many members, this can be quite tiresome. It
> also becomes difficult to verify that both p and q are the same type.
> 
> So the tag "point" serves as a shorter way to specify 
> "{int x; int y;}".  This shorthand is available only for types that
> have tags (unions, structures, and enums).
> 
> -- 
> Remove del for email



On Tuesday, June 12, 2012 11:45:48 PM UTC+8, Barry Schwarz wrote:
> On Mon, 11 Jun 2012 23:47:42 -0700 (PDT), Zhang Yuan
> <zhabgyuan1993@gmail.com> wrote:
> 
> >charpter6
> >6.1 basic
> >
> >"The tag names this kind of structure, and can be used subsequently as a shorthand for the part of the 
> >declaration in braces. "
> >
> >I don't understand it well.
> >I refer to some native language(Chinese) translated from English.
> >just literal translation.
> >
> >Will you put up an example for me to understand it?
> >Thank you.
> >Forgive me for my silly request.
> 
> This is from K&R II, page 128.
> 
> The example they use is 
>      struct point {int x; int y;};
> 
> In this case, the tag is the token "point" (without the quotes).
> 
> I think the idea they are trying to explain is that if you want to
> define an object of this type, you can use
>      struct point p;
> and if later you need to define another object of this type you can
> use
>      struct point q;
> 
> Compare this with what happens if the structure type has no tag, as in
>      struct {int x; int y;};
> 
> In this case, to define an object of this type you would need
>      struct {int x; int y;} p;
> and for a second object
>      struct {int x; int y;} q;
> 
> If the structure type has many members, this can be quite tiresome. It
> also becomes difficult to verify that both p and q are the same type.
> 
> So the tag "point" serves as a shorter way to specify 
> "{int x; int y;}".  This shorthand is available only for types that
> have tags (unions, structures, and enums).
> 
> -- 
> Remove del for email

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