string literal declaration

[Tagore]

Hi,

I was trying to understand some code and came across a string
literal definition as:
char a[]="abc""def"; // string-1

I had seen eariler only string literal with characters in a single
pair of quotes(") e.g.
char a[]="abcdef"; // string-2

Please clear why string-1 is not showing syntax error and how it is
same as string-2.

Thanks,

[Ian Collins]

The preprocessor will concatenate them.

--
Ian Collins

[Peter Nilsson]

Ian Collins <ian-n...@hotmail.com> wrote:
> >     I was trying to understand some code and came across a
> > string literal definition as:
> > char a[]="abc""def";    // string-1
> >
> >    I had seen eariler only string literal with characters
> > in a single pair of quotes(") e.g.
> >   char a[]="abcdef";     // string-2
> >
> > Please clear why string-1 is not showing syntax error
> > and how it is same as string-2.

Because string literals are concatenated before syntactic and
semantic analysis.

> The preprocessor will concatenate them.

Nit: The compiler will concatenate them. Preprocessors are
usually limited to translation phases 1 through 4. String
concatenation is translation phase 6 [cf 5.1.1.2.]

--
Peter

[Nick]

Peter Nilsson <ai...@acay.com.au> writes:

And the reason for this apparently pointless thing is that it lets you
construct string literals at compile time:

#define NAME "Nick"
char a[] = "Hello " NAME " and welcome"

Combined with the "stringizing" feature and you can can do even more.
--
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[Nick Keighley]

On 20 Apr, 07:42, Nick <3-nos...@temporary-address.org.uk> wrote:
> Peter Nilsson <ai...@acay.com.au> writes:
> > Ian Collins <ian-n...@hotmail.com> wrote:
> >> >     I was trying to understand some code and came across a
> >> > string literal definition as:
> >> > char a[]="abc""def";    // string-1
>
> >> >    I had seen eariler only string literal with characters
> >> > in a single pair of quotes(") e.g.
> >> >   char a[]="abcdef";     // string-2
>
> >> > Please clear why string-1 is not showing syntax error
> >> > and how it is same as string-2.
>
> > Because string literals are concatenated before syntactic and
> > semantic analysis.
>
> >> The preprocessor will concatenate them.
>
> > Nit: The compiler will concatenate them. Preprocessors are
> > usually limited to translation phases 1 through 4. String
> > concatenation is translation phase 6 [cf 5.1.1.2.]
>
> And the reason for this apparently pointless thing is that it lets you
> construct string literals at compile time:
>
> #define NAME "Nick"
> char a[] = "Hello " NAME " and welcome"
>
> Combined with the "stringizing" feature and you can can do even more.

and break up long strings over multiple lines

[Kenneth Brody]

On 4/20/2010 2:42 AM, Nick wrote:
> Peter Nilsson<ai...@acay.com.au> writes:
>
>> Ian Collins<ian-n...@hotmail.com> wrote:
>>>> I was trying to understand some code and came across a
>>>> string literal definition as:
>>>> char a[]="abc""def"; // string-1

[...]

> And the reason for this apparently pointless thing is that it lets you
> construct string literals at compile time:
>
> #define NAME "Nick"
> char a[] = "Hello " NAME " and welcome"
>
> Combined with the "stringizing" feature and you can can do even more.

You forgot about:

char foo[] = "This represents a"
" long string, which"
" won't fit on a"
" single line.";

or
char foo[] = "This is line 1.\n"
"And this is another line.";

--
Kenneth Brody

[Nick]

Kenneth Brody <kenb...@spamcop.net> writes:

> On 4/20/2010 2:42 AM, Nick wrote:
>> Peter Nilsson<ai...@acay.com.au> writes:
>>
>>> Ian Collins<ian-n...@hotmail.com> wrote:
>>>>> I was trying to understand some code and came across a
>>>>> string literal definition as:
>>>>> char a[]="abc""def"; // string-1
> [...]
>> And the reason for this apparently pointless thing is that it lets you
>> construct string literals at compile time:
>>
>> #define NAME "Nick"
>> char a[] = "Hello " NAME " and welcome"
>>
>> Combined with the "stringizing" feature and you can can do even more.
>
> You forgot about:
>
> char foo[] = "This represents a"
> " long string, which"
> " won't fit on a"
> " single line.";

I did indeed

> or
> char foo[] = "This is line 1.\n"
> "And this is another line.";

Which is a huge improvement over:

char foo[] = "This is line 1.

And this is another line.";

Did C ever allow this. I've a hazy feeling some versions might have.

[Keith Thompson]

No C standard ever allowed this, but I think many pre-ANSI compilers
did.

You could also write:

char foo[] = "This is line 1.\n\
And this is another line.";

But that's also quite ugly. Apart from depending critically on the
indentation of the second line (something that's easy to mess up while
maintaining the code), it can become a syntax error if there's any
whitespace after the \.

--
Keith Thompson (The_Other_Keith) ks...@mib.org <http://www.ghoti.net/~kst>
Nokia
"We must do something. This is something. Therefore, we must do this."
-- Antony Jay and Jonathan Lynn, "Yes Minister"