If I have a string say:
myvar[128] = "This is a string";
How do I use sprintf to convert the string so it has 4 spaces padded on
the left like:
" This is a string";
Thanks!
Jun 27 '08
41  12470 
Ben Bacarisse wrote:
"rio" <a@b.cwrites:
<lost of code snipped>
>this seems good
not know if compile
Despite the almost deliberate attempt to obscure the code I spotted
errors in all the versions you posted. Why not take a little more
time, think about the solution, and do some testing?
This guy is notorious for obscuring _all_ of his code, not just C. You
should look at his custom x86 assembler language is alt.lang.asm
sometime. No amount of argument over the years has seemed to convince
him of the benefits of legible code.
"Ben Bacarisse" <be********@bsb .me.ukha scritto nel messaggio
news:87******** ****@bsb.me.uk. ..
"rio" <a@b.cwrites:
<lost of code snipped>
>this seems good
not know if compile
Despite the almost deliberate attempt to obscure the code I spotted
errors in all the versions you posted. Why not take a little more
time, think about the solution, and do some testing?
????
i miss all your post in my server news that correct myself
the only one that answe me that i see is this one above
have you not good news server? :)
anyway the last one should be correct if i add
if(d==0) goto l0;
--
Ben.
On Mon, 09 Jun 2008 18:57:04 -0400, nospam <no@spam.comwro te:
>If I have a string say:
myvar[128] = "This is a string";
How do I use sprintf to convert the string so it has 4 spaces padded on
the left like:
" This is a string";
Thanks!
As long as your array is at least twice as long as (your string plus
the number of spaces to insert):
sprintf(myvar+6 4, "%s", myvar);
sprintf(myvar, " %s", myvar+64);
Remove del for email
"rio" <a@b.cha scritto nel messaggio
news:48******** *************** @reader1.news.t in.it...
>
"Ben Bacarisse" <be********@bsb .me.ukha scritto nel messaggio
news:87******** ****@bsb.me.uk. ..
>"rio" <a@b.cwrites:
<lost of code snipped>
>>this seems good
not know if compile
Despite the almost deliberate attempt to obscure the code I spotted
errors in all the versions you posted. Why not take a little more
time, think about the solution, and do some testing?
I have not the C compiler here under my hands
so i write code without testing
????
i miss all your post in my server news that correct myself
the only one that answe me that i see is this one above
have you not good news server? :)
anyway the last one should be correct if i add
if(d==0) goto l0;
better if(d==0) return 0;
Don't you like my last creation? it will be not much fast
/*
d should be mallocched or 0
e.g.
char *d=0;
unsigned sz=0;
----
if((sz=the4spac es(&d, sz, string))==0) error();
free(*d);
----------
*/
%define SPAZI 4
unsigned the4spaces(char ** d, unsigned sz, char* s)
{char *p1, *p2, p;
unsigned c, r;
/*************** *****/
if(d==0||SPAZI< 0) return 0;
if(s==0) goto l0;
if( (int) (c=strlen(s)) < 0) goto l0;
r=sz; p=*d;
if(c+SPAZI +1<sz)
{if( (p=realloc(*d, c+8))==0 )
{l0:; free(*d); *d=0; return 0;}
r=c+8; *d=p;}
p1=s; p2=p;
while( *p1 && (*p1==' '||*p1=='\t')) ++p1;
for(c=0; c<SPAZI ; ++c, ++p2) *p2=' '
while(*p2++=*p1 ++);
return r;}
"rio" <a@b.cha scritto nel messaggio
news:48******** *************** @reader4.news.t in.it...
>"Ben Bacarisse" <be********@bsb .me.ukha scritto nel messaggio
news:87******* *****@bsb.me.uk ...
>>"rio" <a@b.cwrites:
So how many errors do you see?
[whithout use the compiler and with the use of the compiler]
/*
d should be mallocched or 0
e.g.
char *d=0;
unsigned sz=0;
----
if((sz=the4spac es(&d, sz, string))==0) error();
free(*d);
----------
*/
%define SPAZI 4
unsigned the4spaces(char ** d, unsigned sz, char* s)
{char *p1, *p2, p;
unsigned c, r;
/*************** *****/
if(d==0||SPAZI< 0) return 0;
if(s==0) goto l0;
if( (int) (c=strlen(s)) < 0) goto l0;
r=sz; p=*d;
if(c+SPAZI +1<sz)
{if( (p=realloc(*d, c+ SPAZI+8))==0 )
{l0:; free(*d); *d=0; return 0;}
r=c+ SPAZI +8; *d=p;}
p1=s; p2=p;
while( *p1 && (*p1==' '||*p1=='\t')) ++p1;
for(c=0; c<SPAZI ; ++c, ++p2) *p2=' '
while(*p2++=*p1 ++);
return r;}
Barry Schwarz <sc******@dqel. comwrites:
On Mon, 09 Jun 2008 18:57:04 -0400, nospam <no@spam.comwro te:
>>If I have a string say:
myvar[128] = "This is a string";
How do I use sprintf to convert the string so it has 4 spaces padded on
the left like:
" This is a string";
As long as your array is at least twice as long as (your string plus
the number of spaces to insert):
sprintf(myvar+6 4, "%s", myvar);
sprintf(myvar, " %s", myvar+64);
I don't think that is permitted:
7.19.6.6 The sprintf function
... If copying takes place between objects that overlap, the
behavior is undefined.
It does not say "between /regions/ of objects that overlap". It seems
any overlap is enough to render it undefined.
--
Ben.
rio wrote:
"rio" <a@b.cha scritto nel messaggio
news:48******** *************** @reader4.news.t in.it...
>>"Ben Bacarisse" <be********@bsb .me.ukha scritto nel messaggio
news:87****** ******@bsb.me.u k...
"rio" <a@b.cwrites:
So how many errors do you see?
[whithout use the compiler and with the use of the compiler]
That's the problem with code and coding style: without running it thru a
compiler it is next to impossibe to detect the bugs.
Your code is just not writte for human consumption, and even you have
problems with it, hence the multiple versions you post to correct yourself.
Bye, Jojo
Ben Bacarisse wrote:
CBFalconer <cb********@yah oo.comwrites:
>Ben Bacarisse wrote:
>>CBFalconer <cb********@yah oo.comwrites:
... snip ...
>>>
void sstretch(char *s, int amount) {
char *p1, *p2;
if (amount) {
pi = strchr(s, '\0');
if ((p1 s) && amount) {
p2 = p1 + amount;
do { /* move the string */
*p2-- = *p1--;
} while {p1 s);
}
while (amount) { /* inject the blanks */
*s++ = ' ';
amount--;
}
}
} /* untested */
Yuck. Two typos and two logic errors. You complain about not
posting corrections, so the correction is:
.... snip ...
>>
One does it for the exercise.
But if you don't test it (or think about it enough) you get only the
illusion of exercising your C brain whereas, in fact, you are just
putting on "bug flab".
>I see only one typo [while {p1 s)]] and one unnecessary test
[&& amount]. A compilation may well show up more. What did you see?
pi in place of p1. The two logic bugs are:
(1) the loop does not run to the end -- you leave an un-copied
character. Note that this is slightly trick to correct.
(2) when the original string is empty (and amount 0) you just
write spaces over the null.
More than I expected. I guess I am getting sloppy. Well, I did
mark it 'untested', and say 'something like this'. :-)
--
[mail]: Chuck F (cbfalconer at maineline dot net)
[page]: <http://cbfalconer.home .att.net>
Try the download section.
** Posted from http://www.teranews.com **
On Tue, 10 Jun 2008 19:27:31 +0100, Ben Bacarisse
<be********@bsb .me.ukwrote:
>Barry Schwarz <sc******@dqel. comwrites:
>On Mon, 09 Jun 2008 18:57:04 -0400, nospam <no@spam.comwro te:
>>>If I have a string say:
myvar[128] = "This is a string";
How do I use sprintf to convert the string so it has 4 spaces padded on
the left like:
" This is a string";
As long as your array is at least twice as long as (your string plus
the number of spaces to insert):
sprintf(myvar+6 4, "%s", myvar);
sprintf(myvar, " %s", myvar+64);
I don't think that is permitted:
7.19.6.6 The sprintf function
... If copying takes place between objects that overlap, the
behavior is undefined.
It does not say "between /regions/ of objects that overlap". It seems
any overlap is enough to render it undefined.
It seems that the term "object" is not used with great precision here.
What would happen if myvar were defined as
char myvar[2][64] = {"This ..."};
and in the calls to sprintf each use of myvar was cast to char*?
myvar[0] and [1] are objects that do not overlap but both are part of
the object myvar. Is this overlap? Would it be overlap if the
arguments were changed to myvar[0] and myvar[1]?
What about
char *myvar = malloc(128);
strcpy(myvar, "This ...");
There are no objects here so no objects can overlap.
The compiler will probably generate the same code for the three sets
of calls to sprintf. It doesn't seem right (tm) that the same code
generated from essentially identical source statements should be
undefined, questionable, and well defined, respectively.
I will assert that the intent of the word object in this section is
meant to refer to the source and destination strings and therefore
under the conditions I postulated there is no overlap.
Remove del for email
Barry Schwarz <sc******@dqel. comwrites:
On Tue, 10 Jun 2008 19:27:31 +0100, Ben Bacarisse
<be********@bsb .me.ukwrote:
>>Barry Schwarz <sc******@dqel. comwrites:
>>On Mon, 09 Jun 2008 18:57:04 -0400, nospam <no@spam.comwro te:
If I have a string say:
myvar[128] = "This is a string";
How do I use sprintf to convert the string so it has 4 spaces padded on
the left like:
" This is a string";
As long as your array is at least twice as long as (your string plus
the number of spaces to insert):
sprintf(myvar+6 4, "%s", myvar);
sprintf(myvar, " %s", myvar+64);
I don't think that is permitted:
7.19.6.6 The sprintf function
... If copying takes place between objects that overlap, the
behavior is undefined.
It does not say "between /regions/ of objects that overlap". It seems
any overlap is enough to render it undefined.
It seems that the term "object" is not used with great precision here.
What would happen if myvar were defined as
char myvar[2][64] = {"This ..."};
and in the calls to sprintf each use of myvar was cast to char*?
myvar[0] and [1] are objects that do not overlap but both are part of
the object myvar. Is this overlap? Would it be overlap if the
arguments were changed to myvar[0] and myvar[1]?
What about
char *myvar = malloc(128);
strcpy(myvar, "This ...");
There are no objects here so no objects can overlap.
The compiler will probably generate the same code for the three sets
of calls to sprintf. It doesn't seem right (tm) that the same code
generated from essentially identical source statements should be
undefined, questionable, and well defined, respectively.
I will assert that the intent of the word object in this section is
meant to refer to the source and destination strings and therefore
under the conditions I postulated there is no overlap.
These are good points, but I think the wording is clear that the
behaviour is undefined. The intent may not be this wide, but the word
"object" must mean the whole object, surely?
The same wording is used for memcpy, so if it is generally agreed that
memcpy can be used to copy from one place to another non-overlapping
place /within/ a single object, then I agree your solution is OK.
--
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