toupper wont work

[ben]

Hi

Im gettting run time error (Unhandled exeption, access violations) when
executing the following code:

#include <conio.h>
#include <stdio.h>
#include <ctype.h>
#include <string>
#include <stdlib.h>

int main()
{

char *t="test";

printf(t);

*t = toupper(*t); //error here

printf(t);

getch();
return 0;

}
I running it on VC++ 6

All I want to do is to convert a string to upper case. Am I missing
something here?

Thanks

[John Carson]

Re: toupper wont work

"ben" <ben@ben.com> wrote in message
news:d%AZb.3045 7$fW.22950@twis ter.rdc-kc.rr.com[color=blue]
> Hi
>
> Im gettting run time error (Unhandled exeption, access violations)
> when executing the following code:
>
> #include <conio.h>
> #include <stdio.h>
> #include <ctype.h>
> #include <string>
> #include <stdlib.h>
>
> int main()
> {
>
> char *t="test";
>
> printf(t);
>
> *t = toupper(*t); //error here
>
> printf(t);
>
> getch();
> return 0;
>
> }
> I running it on VC++ 6
>
> All I want to do is to convert a string to upper case. Am I missing
> something here?
>
> Thanks[/color]

toupper doesn't convert strings, it converts characters. As it happens, this
is not your problem. Your problem is that

char *t="test";

creates a pointer to a string literal that is stored in read-only memory.
Thus you cannot change it. What you need is:

char t[]="test";

which creates a writeable array.


--
John Carson
1. To reply to email address, remove donald
2. Don't reply to email address (post here instead)

[ben]

Re: toupper wont work

thanks, it worked

"John Carson" <donaldquixote@ datafast.net.au > wrote in message
news:4036e008@u senet.per.parad ox.net.au...[color=blue]
> "ben" <ben@ben.com> wrote in message
> news:d%AZb.3045 7$fW.22950@twis ter.rdc-kc.rr.com[color=green]
> > Hi
> >
> > Im gettting run time error (Unhandled exeption, access violations)
> > when executing the following code:
> >
> > #include <conio.h>
> > #include <stdio.h>
> > #include <ctype.h>
> > #include <string>
> > #include <stdlib.h>
> >
> > int main()
> > {
> >
> > char *t="test";
> >
> > printf(t);
> >
> > *t = toupper(*t); //error here
> >
> > printf(t);
> >
> > getch();
> > return 0;
> >
> > }
> > I running it on VC++ 6
> >
> > All I want to do is to convert a string to upper case. Am I missing
> > something here?
> >
> > Thanks[/color]
>
> toupper doesn't convert strings, it converts characters. As it happens,[/color]
this[color=blue]
> is not your problem. Your problem is that
>
> char *t="test";
>
> creates a pointer to a string literal that is stored in read-only memory.
> Thus you cannot change it. What you need is:
>
> char t[]="test";
>
> which creates a writeable array.
>
>
> --
> John Carson
> 1. To reply to email address, remove donald
> 2. Don't reply to email address (post here instead)
>
>[/color]

[Frank Schmitt]

Re: toupper wont work

"ben" <ben@ben.com> writes:
[color=blue]
> Hi
>
> Im gettting run time error (Unhandled exeption, access violations) when
> executing the following code:
>
> #include <conio.h>
> #include <stdio.h>
> #include <ctype.h>
> #include <string>
> #include <stdlib.h>
>
> int main()
> {
>
> char *t="test";
>
> printf(t);[/color]

This is asking for trouble - use
print("%s",t);[color=blue]
>
> *t = toupper(*t); //error here
>
> printf(t);
>
> getch();
> return 0;
>[/color]

Better yet, get rid of C-style strings altogether and use C++ strings
and I/O:

#include <cctype>
#include <string>
#include <iostream>

int main() {

std::string t = "test";
std::cout << t << "\n";
for (std::size_t i=0; i<t.length(); ++i)
t[i] = std::toupper(t[i]);
std::cout << t << std::endl;
return 0;
}

HTH & kind regards
frank

--
Frank Schmitt
quattro research GmbH
e-mail: schmitt NO at SPAM quattro-research !@! dot com

[Dietmar Kuehl]

Re: toupper wont work

Pete Becker <petebecker@acm .org> wrote:[color=blue]
> Frank Schmitt wrote:[color=green][color=darkred]
> > > char *t="test";
> > > printf(t);[/color]
> >
> > This is asking for trouble - use
> > print("%s",t);[/color]
>
> There's nothing wrong wtih printf(t).[/color]

Well, in this case there is nothing wrong with 'printf(t)'. If 't' is obtained
from somewhere, eg. from user input, it is not really a bright idea to use
't' as format string, however: it may contain formatting directives by
accident in which case the call to 'printf(t)' might easily yield funny
behavior.

Of course, this is not really related to the original problem which was
writing to string literal. The other problem not yet noted in this thread
was the fact that 'char' may be signed but 'toupper()' has to be called with
an 'unsigned char' or EOF (this is described in 7.4 paragraph 1 of the current
C standard; I don't have the C90 standard but I'm sure the same rule applies
there, too). Thus, the program should look something like this:

char t[] = "test";
for (char* it = t; *it; ++it)
*it = std::toupper(st atic_cast<unsig ned char>(*it));

Of course, for "test" it is again unlikely to make any difference because
normally these characters happen to be represented by ASCII which uses all
positive values. However, in a real application the characters may include
non-ASCII character which may have negative values. Of course, in this case
there may be other problems as well: for example, the string may include the
German "sz" ligature for which there is no single character uppercase variant.
The uppercase variante of the "sz" ligature (which is just one character) has
two characters.
--
<mailto:dietmar _kuehl@yahoo.co m> <http://www.dietmar-kuehl.de/>
Phaidros eaSE - Easy Software Engineering: <http://www.phaidros.co m/>