Hi all,
why does C language permits an extra comma in initializer list
ex:- int days[] = {
31,28.31,30,31, 30,
31,31,30,31,30, 31,
}
i have heard it is for the purpose of automatic code generation
is there any other purpose than this, if so why ...????
22  3600  aa*****@gmail.c om said:
Hi all,
why does C language permits an extra comma in initializer list
ex:- int days[] = {
31,28.31,30,31, 30,
Between 31 and 28 you meant ,, not ..
31,31,30,31,30, 31,
}
i have heard it is for the purpose of automatic code generation
That's supposed to be the reasoning behind such lamenesses, yes. But
observe:
i = 0;
printf(" %d", day[i]);
while(i++ < 12)
{
printf(", %d%s", day[i], (i % 6) == 5 ? "\n" : "");
}
So, as you can see, it isn't actually difficult to generate the code
without the trailing comma.
is there any other purpose than this, if so why ...????
No, it's just catering for the lazy.
--
Richard Heathfield <http://www.cpax.org.uk >
Email: -http://www. +rjh@
Google users: <http://www.cpax.org.uk/prg/writings/googly.php>
"Usenet is a strange place" - dmr 29 July 1999
On Feb 16, 7:14 pm, Richard Heathfield <r...@see.sig.i nvalidwrote:
aark...@gmail.c om said:
Hi all,
why does C language permits an extra comma in initializer list
ex:- int days[] = {
31,28.31,30,31, 30,
Between 31 and 28 you meant ,, not ..
How do you know? 28.31 is a valid value for initializing in integer
context.
>
31,31,30,31,30, 31,
}
i have heard it is for the purpose of automatic code generation
That's supposed to be the reasoning behind such lamenesses, yes. But
observe:
i = 0;
printf(" %d", day[i]);
while(i++ < 12)
{
printf(", %d%s", day[i], (i % 6) == 5 ? "\n" : "");
}
So, as you can see, it isn't actually difficult to generate the code
without the trailing comma.
Modulus or even the conditional check could be expensive somewhere I
guess.
Notice it's not only allowed in an "initialize r list" but anywhere
where {elements} is used. (I don't know the proper term for it)
For example, printf("%zu\n", sizeof (char[]){1,2,3,});
On Feb 16, 4:55*pm, aark...@gmail.c om wrote:
why does C language permits an extra comma in initializer list
...
*i have heard it is for the purpose of automatic code generation
is there any other purpose than this, if so why ...????
According to K&R2 (p196) it is "a nicety for neat formatting."
--
Martin vi******@gmail. com said:
On Feb 16, 7:14 pm, Richard Heathfield <r...@see.sig.i nvalidwrote:
>aark...@gmail. com said:
Hi all,
why does C language permits an extra comma in initializer list
ex:- int days[] = {
31,28.31,30,31, 30,
Between 31 and 28 you meant ,, not ..
How do you know?
Call me psychic if you like.
28.31 is a valid value for initializing in integer
context.
Yes, but on this occasion it was not what was intended.
<snip>
>So, as you can see, it isn't actually difficult to generate the code
without the trailing comma.
Modulus or even the conditional check could be expensive somewhere I
guess.
My % could have been avoided if necessary, but in any case it was to deal
with the newline, not the comma.
--
Richard Heathfield <http://www.cpax.org.uk >
Email: -http://www. +rjh@
Google users: <http://www.cpax.org.uk/prg/writings/googly.php>
"Usenet is a strange place" - dmr 29 July 1999
Richard Heathfield <rj*@see.sig.in validwrites: aa*****@gmail.c om said:
>why does C language permits an extra comma in initializer list
i have heard it is for the purpose of automatic code generation
That's supposed to be the reasoning behind such lamenesses, yes. But
observe:
i = 0;
printf(" %d", day[i]);
while(i++ < 12)
{
printf(", %d%s", day[i], (i % 6) == 5 ? "\n" : "");
}
Observe:
int array[] = {
#ifdef ELEMENT_ONE
1,
#endif
#ifdef ELEMENT_TWO
2,
#endif
#ifdef ELEMENT_THREE
3,
#endif
#ifdef ELEMENT_FOUR
4,
#endif
};
versus:
int array[] = {
#ifdef ELEMENT_ONE
1
# if (defined(ELEMEN T_TWO) || defined(ELEMENT _THREE) \
|| defined(ELEMENT _FOUR))
,
# endif
#endif
#ifdef ELEMENT_TWO
2,
# if defined(ELEMENT _THREE) || defined(ELEMENT _FOUR)
,
# endif
#endif
#ifdef ELEMENT_THREE
3
# if defined(ELEMENT _FOUR)
,
# endif
#endif
#ifdef ELEMENT_FOUR
4,
#endif
};
I know which one I would prefer to maintain.
--
"The expression isn't unclear *at all* and only an expert could actually
have doubts about it"
--Dan Pop
Ben Pfaff said:
Richard Heathfield <rj*@see.sig.in validwrites:
<snip>
I know which one I would prefer to maintain.
Surely the whole point of generating the code automatically is that you
don't have to maintain it?
--
Richard Heathfield <http://www.cpax.org.uk >
Email: -http://www. +rjh@
Google users: <http://www.cpax.org.uk/prg/writings/googly.php>
"Usenet is a strange place" - dmr 29 July 1999
Richard Heathfield <rj*@see.sig.in validwrites:
Ben Pfaff said:
>Richard Heathfield <rj*@see.sig.in validwrites:
<snip>
>I know which one I would prefer to maintain.
Surely the whole point of generating the code automatically is that you
don't have to maintain it?
The code that you snipped was not an example of automatically
generated code.
--
"Welcome to the wonderful world of undefined behavior, where the demons
are nasal and the DeathStation users are nervous." --Daniel Fox
Ben Pfaff said:
Richard Heathfield <rj*@see.sig.in validwrites:
>Ben Pfaff said:
>>Richard Heathfield <rj*@see.sig.in validwrites:
<snip>
>>I know which one I would prefer to maintain.
Surely the whole point of generating the code automatically is that you
don't have to maintain it?
The code that you snipped was not an example of automatically
generated code.
Oh. I see.
<bright smile, a la Dory from "Finding Nemo">
Well then - perhaps you ought to automate it! :-)
--
Richard Heathfield <http://www.cpax.org.uk >
Email: -http://www. +rjh@
Google users: <http://www.cpax.org.uk/prg/writings/googly.php>
"Usenet is a strange place" - dmr 29 July 1999
Richard Heathfield <rj*@see.sig.in validwrites:
Ben Pfaff said:
>Richard Heathfield <rj*@see.sig.in validwrites:
>>Ben Pfaff said:
Richard Heathfield <rj*@see.sig.in validwrites:
<snip>
I know which one I would prefer to maintain.
Surely the whole point of generating the code automatically is that you
don't have to maintain it?
The code that you snipped was not an example of automatically
generated code.
Oh. I see.
<bright smile, a la Dory from "Finding Nemo">
Well then - perhaps you ought to automate it! :-)
Fortunately, I have no need to do so, because trailing commas are
allowed in initializer lists (and elsewhere).
--
char a[]="\n .CJacehknorstu" ;int putchar(int);in t main(void){unsi gned long b[]
={0x67dffdff,0x 9aa9aa6a,0xa77f fda9,0x7da6aa6a ,0xa67f6aaa,0xa a9aa9f6,0x11f6} ,*p
=b,i=24;for(;p+ =!*p;*p/=4)switch(0[p]&3)case 0:{return 0;for(p--;i--;i--)case+
2:{i++;if(i)bre ak;else default:continu e;if(0)case 1:putchar(a[i&15]);break;}}} This thread has been closed and replies have been disabled. Please start a new discussion. Similar topics | |
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