a little mistake

[ash]

i am writing this program (for exercise1-9 in k&r-2nd edition) which
removes extra spaces in string
example- "test string" will be "test string"

#include<stdio. h>
#include<string .h>
#include<conio. h>
main()
{
char str[20],st[20];
int i=0,j=0;
printf("enter string");
gets(str);

while(str[i]!=NULL)
{
if(str[i]==' ')
{ st[j++]=st[i++];

while(str[i]==' ') i++;

}
else
st[j++]=str[i++];
}
st[j]=NULL;
strcpy(str,st);
puts(str);
}

(compiled in turbo c++ for windows version 3.1)
i know there should be other ways to write this program (thats a bad
program ),can someone help me in writing that program in compact way
and give me some logic and tips.
i want to use gcc but i don`t have linux operating system and one
software which allows gcc compiling in windows (cygwin) is not working.
anyone can advice me such a program that allows compiling with gcc in
windows( this is off topic but advices are always welcome).

thankx

[Malcolm]

"ash" <as************ @rediffmail.com > wrote in message
news:11******** **************@ i40g2000cwc.goo glegroups.com.. .

i am writing this program (for exercise1-9 in k&r-2nd edition) which
removes extra spaces in string
example- "test string" will be "test string"

#include<stdio. h>
#include<string .h>
#include<conio. h>
main()
{
char str[20],st[20];
int i=0,j=0;
printf("enter string");
gets(str);

while(str[i]!=NULL)
{
if(str[i]==' ')
{ st[j++]=st[i++];

while(str[i]==' ') i++;

}
else
st[j++]=str[i++];
}
st[j]=NULL;
strcpy(str,st);
puts(str);
}

(compiled in turbo c++ for windows version 3.1)
i know there should be other ways to write this program (thats a bad
program ),can someone help me in writing that program in compact way
and give me some logic and tips.
i want to use gcc but i don`t have linux operating system and one
software which allows gcc compiling in windows (cygwin) is not working.
anyone can advice me such a program that allows compiling with gcc in
windows( this is off topic but advices are always welcome).

thankx

Separate out ewhat you are doing into a function.

In this case you want

/*
turns whitespace spans into single spaces
(and trims leading / trailing white space?)
*/
void onespace(char *out, char *in)

Decide if you want to allow out and in to be the same. This will make your
function
more convenient to use, but you might have to be a little bit more careful
in coding it.

Basically you maintain two pointer, a "write" pointer and a "read" pointer.
If you hit
a non-whitespace you write to the "write" pointer and increment both.
If you hit a whitespace character, you write a single space to the "write"
pointer. Then you increment the "read" pointer whilst it is still pointing
to white space.
--
Buy my book 12 Common Atheist Arguments (refuted)
$1.25 download or $7.20 paper, available www.lulu.com/bgy1mm

[santosh]

ash wrote:
.... snip ...

i want to use gcc but i don`t have linux operating system and one
software which allows gcc compiling in windows (cygwin) is not working.
anyone can advice me such a program that allows compiling with gcc in
windows( this is off topic but advices are always welcome).

Generally Cygwin is a bit complex to set up and use. Use MinGW instead.
It uses native Win32 ports of the GNU toolchain.

http://www.mingw.org/

[Keith Thompson]

"ash" <as************ @rediffmail.com > writes:

i am writing this program (for exercise1-9 in k&r-2nd edition) which
removes extra spaces in string
example- "test string" will be "test string"

#include<stdio. h>
#include<string .h>
#include<conio. h>
<conio.h> is not a standard header. You don't use it anyway. Delete
the above line.

I find it clearer to leave a space between "include" and "<".
main()
int main(void)
{
char str[20],st[20];
int i=0,j=0;
printf("enter string");
Since this doesn't end in a newline, it's not guaranteed to appear.
Add "fflush(stdout) ;".

I'd add a blank, or perhaps ": ", at the end of the prompt; it looks
better. Without it, if I type "foo", I see "enter stringfoo" on the
screen.
gets(str);
Never use gets(). Never use gets(). Never use gets().

See question 12.23 in the comp.lang.c FAQ, <http://www.c-faq.com/>.
while(str[i]!=NULL)
NULL is a null pointer constant. You're trying to compare a character
value to a pointer value. It happens to work on your system for
obscure reasons I won't get into, but it's bad style at the very
least. The way to represent a null character is '\0'.
{
if(str[i]==' ')
{ st[j++]=st[i++];
I think you mean "st[j++]=st[i++];"

while(str[i]==' ') i++;

}
else
st[j++]=str[i++];
}
st[j]=NULL;
Again, use '\0', not NULL.
strcpy(str,st);
puts(str);
return 0;
}

And don't underestimate the importance of consistent formatting,
particularly indentation.

Apart from that, the program doesn't seem unreasonable.

--
Keith Thompson (The_Other_Keit h) ks***@mib.org <http://www.ghoti.net/~kst>
San Diego Supercomputer Center <*> <http://users.sdsc.edu/~kst>
We must do something. This is something. Therefore, we must do this.

[Default User]

ash wrote:

i am writing this program (for exercise1-9 in k&r-2nd edition) which
removes extra spaces in string
example- "test string" will be "test string"
That's not the actual exercise:

Exercise 1-9. Write a program to copy its input to its output,
replacing each string of one or more blanks by a single blank.


#include<stdio. h>
#include<string .h>
#include<conio. h>
<conio.h> is not a standard header. You should not use it, as it's not
very portable.
main()
Use the following form:

int main(void)
{
char str[20],st[20];
These fixed buffers are likely a problem.
int i=0,j=0;
printf("enter string");
gets(str);
Never, ever use gets(). It's dangerous. What happens when someone
enters a string with 50 characters? Bad things.

while(str[i]!=NULL)
NULL is a null pointer constant. It might be 0, which would work, but
it could be (void*)0. Either use '\0' or 0 in checking for the null
terminator in a string.
{
if(str[i]==' ')
{ st[j++]=st[i++];

while(str[i]==' ') i++;

}
else
st[j++]=str[i++];
}
st[j]=NULL;
strcpy(str,st);
puts(str);
}

(compiled in turbo c++ for windows version 3.1)
i know there should be other ways to write this program (thats a bad
program ),can someone help me in writing that program in compact way
and give me some logic and tips.
i want to use gcc but i don`t have linux operating system and one
software which allows gcc compiling in windows (cygwin) is not
working. anyone can advice me such a program that allows compiling
with gcc in windows( this is off topic but advices are always
welcome).

Do you want the program that K&R assigned, or the one you tried? It can
be made much more simple by just immediately outputting characters
instead of copying to buffers.

/* algorithm portion */

int c;
int flag = 0;

while ((c = getchar()) != EOF)
{
if (c == ' ')
{
if (flag == 0)
{
putchar(c);
flag = 1;
}
}
else
{
if (flag == 1)
{
flag = 0;
}
putchar(c);
}
}

Brian

[CBFalconer]

ash wrote:

.... snip ...
i want to use gcc but i don`t have linux operating system and one
software which allows gcc compiling in windows (cygwin) is not
working. anyone can advice me such a program that allows compiling
with gcc in windows( this is off topic but advices are always
welcome).

djgpp, at <http://www.delorie.com >. However cygwin should work.

--
"A man who is right every time is not likely to do very much."
-- Francis Crick, co-discover of DNA
"There is nothing more amazing than stupidity in action."
-- Thomas Matthews

[Julian V. Noble]

Malcolm wrote:

"ash" <as************ @rediffmail.com > wrote in message
news:11******** **************@ i40g2000cwc.goo glegroups.com.. .

i am writing this program (for exercise1-9 in k&r-2nd edition) which
removes extra spaces in string
example- "test string" will be "test string"

#include<stdio. h>
#include<string .h>
#include<conio. h>
main()
{
char str[20],st[20];
int i=0,j=0;
printf("enter string");
gets(str);

while(str[i]!=NULL)
{
if(str[i]==' ')
{ st[j++]=st[i++];

while(str[i]==' ') i++;

}
else
st[j++]=str[i++];
}
st[j]=NULL;
strcpy(str,st);
puts(str);
}

(compiled in turbo c++ for windows version 3.1)
i know there should be other ways to write this program (thats a bad
program ),can someone help me in writing that program in compact way
and give me some logic and tips.
i want to use gcc but i don`t have linux operating system and one
software which allows gcc compiling in windows (cygwin) is not working.
anyone can advice me such a program that allows compiling with gcc in
windows( this is off topic but advices are always welcome).

thankx

Separate out ewhat you are doing into a function.

In this case you want

/*
turns whitespace spans into single spaces
(and trims leading / trailing white space?)
*/
void onespace(char *out, char *in)

Decide if you want to allow out and in to be the same. This will make your
function
more convenient to use, but you might have to be a little bit more careful
in coding it.

Basically you maintain two pointer, a "write" pointer and a "read" pointer.
If you hit
a non-whitespace you write to the "write" pointer and increment both.
If you hit a whitespace character, you write a single space to the "write"
pointer. Then you increment the "read" pointer whilst it is still pointing
to white space.

I think you also need a little state machine: if you have not hit
a blank you are in character-accepting mode and write that char
to the buffer where you construct the compacted string. Otherwise
if the char is a blank you accept it but shift to a mode where you
no longer accept blank characters. When you hit a non-blank you
switch back to the first mode. In other words,

state\input -> non-blank blank
// --------------------------------------------------------
1 write to buff write to buff and
set state to 2

2 write to buff and drop char
set state to 1
// --------------------------------------------------------

A switch statement and a state variable will accomplish this.
--
Julian V. Noble
Professor Emeritus of Physics
University of Virginia

[lovecreatesbeauty]

ash wrote:

can someone help me in writing that program in compact way
and give me some logic and tips.

I don't know whether my program is compact or not, anyway code below
it's my own. Suggestion welcomed.
/* Removes extra spaces in string pointed by src, the result string is
pointed by dst. Return value is the length os the result string or
0 for failure. example: "test string" will be "test string" */
int spacerm(char *dst, char *src)
{
int last_space = 0; /*1: last char is a space char; 0: not*/
int len = 0;
int ret = 1; /*for return value, 0: failure, non-zero: result
string length returned*/

if (src == 0 || dst == 0)
{
ret = 0;
}

if (ret != 0)
{
while (*src != '\0')
{
if (*src == ' ')
{
if (last_space != 1)
{
*dst++ = *src++;
len++;
}
else
{
src++;
}

last_space = 1;

}
else
{
*dst++ = *src++;
len++;
last_space = 0;
}
}

ret = len;
}

return ret;
}

#include <stdio.h>
#include <string.h>
int main(void)
{
char *s = "test string";
char a[20] = {'\0'};
int i = 0;

printf("%i, %s\n", strlen(s), s);
i = spacerm(a, s);
printf("%i, %s\n", i, a);

return 0;
}

$ gcc -W -Wall -pedantic -ansi test.c
$ ./a.out
14, test string
11, test string
$

i want to use gcc but i don`t have linux operating system and one
software which allows gcc compiling in windows (cygwin) is not working.
anyone can advice me such a program that allows compiling with gcc in
windows( this is off topic but advices are always welcome).

Use mingw or Install a Debian Linux on VMware hosted in Windows.

lovecreatesbeau ty

[Peter Nilsson]

lovecreatesbeau ty wrote:

/* Removes extra spaces in string pointed by src, the result string is
pointed by dst. Return value is the length os the result string or
0 for failure. example: "test string" will be "test string" */
What if the original string is "". Is that an error? If so, why?
int spacerm(char *dst, char *src)
{
int last_space = 0; /*1: last char is a space char; 0: not*/
int len = 0;
int ret = 1; /*for return value, 0: failure, non-zero: result
string length returned*/
You effectively have two variables for the same thing. This
looks clumsy.
if (src == 0 || dst == 0)
Why bother? [Rehtorical]
{
ret = 0;
}

if (ret != 0)
{
while (*src != '\0')
{
if (*src == ' ')
{
if (last_space != 1)
if (last_space == 0)

Apart from being more efficient on many systems, it's
obvious what the test is. When you test explicitly against
a value like 1, the reader may pause to ponder whether
the variable can other values like 2 or 3 and why 1 is
significant.
{
*dst++ = *src++;
len++;
}
else
{
src++;
}

last_space = 1;

}
else
{
*dst++ = *src++;
len++;
last_space = 0;
}
}
You never write a terminating null byte to dst.
ret = len;
}

return ret;
}

#include <stdio.h>
#include <string.h>
int main(void)
{
char *s = "test string";
char a[20] = {'\0'};
Try...

char a[20] = "xxxxxxxxxxxWha t?";
int i = 0;

printf("%i, %s\n", strlen(s), s);
strlen() returns a size_t value; %i expects an int.

In C99 use %zu to print a size_t. In C90, cast the value
to suitable unsigned type and use %u with an appropriate
length modifier.
i = spacerm(a, s);
printf("%i, %s\n", i, a);

return 0;
}

$ gcc -W -Wall -pedantic -ansi test.c
Not a blip eg? Safe as houses then.

As some non-expert whose comments aren't worth the
em waves they're transmitted in once said "You control
the portability of your code, not gcc." <g>
$ ./a.out
14, test string
11, test string
$

--
Peter

[Frederick Gotham]

ash posted:

i am writing this program (for exercise1-9 in k&r-2nd edition) which
removes extra spaces in string
example- "test string" will be "test string"

I'd probably approach it something like:

#include <cstddef>

void RetreatStrXPlac es(register char *p, std::size_t const places)
{
/* Consider coding this by copying int's
and checking if any byte is a space
character */

if ( !places ) return;

register char *q = p - places;

while ( *q++ = *p++ );
}

void FixMultipleSpac es( char * const p_start )
{
for(char *p = p_start; ; )
{
switch( *p++ )
{
case 0: return;

case ' ':
{
unsigned places = 0;

while( *p++ == ' ' ) ++places;

RetreatStrXPlac es(--p, places);
}
}
}
}

#include <iostream>
#include <cstdlib>

int main()
{
using std::cout;

char buffer[] = "The man walked over the revine";

FixMultipleSpac es(buffer);

cout << buffer << '\n';

std::system("PA USE");
}

--

Frederick Gotham