topic Re: C++ SWAP function - help in Operating System - OpenVMS

C++ SWAP function - help

Boniface Chiwenda — Thu, 01 Jul 2004 09:41:45 GMT

Hi every one
I have a problem writting a function which should
be able to output characters which are swapped i.e give then the input 'HELLOW WORLD'
the output should be 'EHLLWO OWLRD' can some one help.

Regards
Bonnie.

Re: C++ SWAP function - help

Hein van den Heuvel — Thu, 01 Jul 2004 10:07:45 GMT

What is the exat problem you are having?
What do you want the swap to do when there is an odd number of characters?

Here is something to get you going.
Works for me (with TWO spaces betweeb HELLOW and WORLD"

#include

swap (char *string_pointer)
{
short temp, *short_pointer;
char c, *p;

p = string_pointer;
short_pointer = (void *) p;
while (*p) {
c = *p++;
if (*p) {
temp = (c << 8) + *p++;
*short_pointer++ = temp;
}
}
}

main() {
char test[]="HELLOW WORLD";
swap(test);
printf ("%s\n", test);
}

$ cc tmp
$ lin tmp
$ run tmp
EHLLWO OWLRD
$

Re: C++ SWAP function - help

Boniface Chiwenda — Thu, 01 Jul 2004 10:22:34 GMT

Great thanks for your help. If the sentence is
of odd number the last character is not switched with anything, but simply attached.

Regards
Bonnie.

Re: C++ SWAP function - help

Antoniov. — Thu, 01 Jul 2004 10:42:29 GMT

Hi Hein,
sorry for disagree another time inthe same week :-o (never happened before!)

Your code is quick but assume short as 16 bit that's is true in current C/C++ but may be false in future (or on other systems).
Also you assume char as 8 bit so your code can't work with wchar (known as unicode).

This code is slower but more secure and more flexible:

swap (char *string_pointer)
{
char c, *p, *p1;

p = string_pointer;
while (*p)
{
p1 = p;
c = *p++;
if (*p)
{
*p1 = *p;
*p = c;
}
}
}

Changing in above code 'char' with 'wchar' function can work using unicode.

Regards
Antonio Vigliotti