Hello everyone,


I am surprised to see that the value of sign ' is the same as \'. So,
there is no need to add sign \ before sign '? In my past knowledge of
sign ', we always need to add sign \ before sign '. Any comments?

Here is my simple program to test.

#include <string.h>

int main (int argc, char** argv)
{
char* p1 = "Hello \'World\'";
char* p2 = "Hello 'World'";
int result = 0;

result = strcmp(p1, p2);

return 0;
}

thanks in advance,
George

George2 wrote:
> Hello everyone,
>
>
> I am surprised to see that the value of sign ' is the same as \'. So,
> there is no need to add sign \ before sign '? In my past knowledge of
> sign ', we always need to add sign \ before sign '. Any comments?

This snippet

char ch = 'a';
printf ("It's Jon%cs\n", ch);

.... prints "It's Jonas". Your mission, should you choose to
accept it, is to change the first line to make the output be
"It's Jon's".

--
Eric Sosman
esosman@ieee-dot-org.invalid

In article <e85dd802-d28c-4c4a-887a-e525b5f19793@a39g2000pre.googlegroups.com>,
George2 <george4academic@yahoo.com> wrote:

>I am surprised to see that the value of sign ' is the same as \'. So,
>there is no need to add sign \ before sign '?

There's no need to put a backslash before a single quote in a string,
but in a character constant you need it:

char *s = "'";
char c = '\'';

Conversely you need a backslash before a double quote in a string, but
not in a character constant:

char *s = "\"";
char c = '"';

You are allowed to use the backslashed forms even when not necessary.

-- Richard
--
"Consideration shall be given to the need for as many as 32 characters
in some alphabets" - X3.4, 1963.

Eric Sosman wrote:
> George2 wrote:
>> Hello everyone,
>>
>>
>> I am surprised to see that the value of sign ' is the same as \'. So,
>> there is no need to add sign \ before sign '? In my past knowledge of
>> sign ', we always need to add sign \ before sign '. Any comments?
>
> This snippet
>
> char ch = 'a';
> printf ("It's Jon%cs\n", ch);
>
> ... prints "It's Jonas". Your mission, should you choose to
> accept it, is to change the first line to make the output be
> "It's Jon's".

How do you propose to make your posting self-destruct?

Mark Bluemel wrote:
> Eric Sosman wrote:
>> George2 wrote:
>>> Hello everyone,
>>>
>>>
>>> I am surprised to see that the value of sign ' is the same as \'. So,
>>> there is no need to add sign \ before sign '? In my past knowledge of
>>> sign ', we always need to add sign \ before sign '. Any comments?
>>
>> This snippet
>>
>> char ch = 'a';
>> printf ("It's Jon%cs\n", ch);
>>
>> ... prints "It's Jonas". Your mission, should you choose to
>> accept it, is to change the first line to make the output be
>> "It's Jon's".
>
> How do you propose to make your posting self-destruct?

Unnecessary; I'll just deny all knowledge.

--
Eric Sosman
esosman@ieee-dot-org.invalid

"George2" <george4academic@yahoo.com> wrote in message
news:e85dd802-d28c-4c4a-887a-e525b5f19793@a39g2000pre.googlegroups.com...
> Hello everyone,
>
>
> I am surprised to see that the value of sign ' is the same as \'. So,
> there is no need to add sign \ before sign '? In my past knowledge of
> sign ', we always need to add sign \ before sign '. Any comments?
>
> Here is my simple program to test.
>
>

> #include <string.h>
>
> int main (int argc, char** argv)
> {
> char* p1 = "Hello \'World\'";
> char* p2 = "Hello 'World'";
> int result = 0;
>
> result = strcmp(p1, p2);
>
> return 0;
> }
>

>

Context, context, context.

char c = '\''; /* apostrophe in character literal */
char *s = "'"; /* apostrophe in string literal */

char c = '"'; /* quote in character literal */
char *s = "\""; /* quote in string literal */

char c = '''; /* invalid */
char *s = """; /* invalid */

-Mike

Eric Sosman wrote:
> George2 wrote:
>> Hello everyone,
>>
>>
>> I am surprised to see that the value of sign ' is the same as \'. So,
>> there is no need to add sign \ before sign '? In my past knowledge of
>> sign ', we always need to add sign \ before sign '. Any comments?
>
> This snippet
>
> char ch = 'a';
> printf ("It's Jon%cs\n", ch);
>
> ... prints "It's Jonas". Your mission, should you choose to
> accept it, is to change the first line to make the output be
> "It's Jon's".
>
char ch = '\'';

--
Joe Wright
"Everything should be made as simple as possible, but not simpler."
--- Albert Einstein ---

"Mike Wahler" <mkwahler@mkwahler.net> a écrit dans le message de news:
13ke17p76urbr54@corp.supernews.com...
>
> "George2" <george4academic@yahoo.com> wrote in message
> news:e85dd802-d28c-4c4a-887a-e525b5f19793@a39g2000pre.googlegroups.com...
>> Hello everyone,
>>
>>
>> I am surprised to see that the value of sign ' is the same as \'. So,
>> there is no need to add sign \ before sign '? In my past knowledge of
>> sign ', we always need to add sign \ before sign '. Any comments?
>>
>> Here is my simple program to test.
>>
>>

>> #include <string.h>
>>
>> int main (int argc, char** argv)
>> {
>> char* p1 = "Hello \'World\'";
>> char* p2 = "Hello 'World'";
>> int result = 0;
>>
>> result = strcmp(p1, p2);
>>
>> return 0;
>> }
>>

>>
>
> Context, context, context.
>
> char c = '\''; /* apostrophe in character literal */
> char *s = "'"; /* apostrophe in string literal */
>
> char c = '"'; /* quote in character literal */
> char *s = "\""; /* quote in string literal */
>
> char c = '''; /* invalid */
> char *s = """; /* invalid */

Since you cannot have an empty character constant, ''' is not ambiguous, so
it could be allowed.

For the OP: now that you understand quoting issues better, how does C handle
triple quoting à la python:

char *s3 = """'""";

And what is wrong with these:

char c2 = '""';
char c3 = '"""';

--
Chqrlie.

Charlie Gordon wrote:
....
> And what is wrong with these:
>
> char c2 = '""';
> char c3 = '"""';

Nothing, as far as I can see, though the value stored in c2 and c3 is
implementation-defined.

Charlie Gordon wrote:
> [...]
> Since you cannot have an empty character constant, ''' is not ambiguous, so
> it could be allowed.

int ch = ''' + ''';

What value do you suggest ch should have? Twice the
value of '\'', or the implementation-defined value of a
character literal containing seven characters, or something
else?

--
Eric Sosman
esosman@ieee-dot-org.invalid

"Eric Sosman" <esosman@ieee-dot-org.invalid> a écrit dans le message de
news: Acudne_NXIY_VtfanZ2dnUVZ_q6mnZ2d@comcast.com...
> Charlie Gordon wrote:
>> [...]
>> Since you cannot have an empty character constant, ''' is not ambiguous,
>> so it could be allowed.
>
> int ch = ''' + ''';
>
> What value do you suggest ch should have? Twice the
> value of '\'', or the implementation-defined value of a
> character literal containing seven characters, or something
> else?

Good point. Thus exits ''' for '\'';

But then why disallow the empty character constant ?
We could make the empty character constant have the value 0. That would
improve readability of code dealing with ends of strings:

if (str[i] == '') {
return i;
}

It would be somewhat consistent with the string literal syntax:

char *s = "";
assert(*s == '');

I'll wait till April 1st, 2008 to submit this one for consideration in C20XY

--
Chqrlie.