K&R2, exercise 1-23

A

arnuld

there are no compile-time errors or warning. it runs but it does not
do what it is supposed to.

WANTED: to print the "input C programme" with all comments removed.

GOT: does not print anything.

-------- PROGRAMME -----------
/* K&R2: exercise 1-23

STATEMENT:
write aprogramme to remove all comments from a C programme
dont forget to handle quoted strings and character constants properly.

METHOD:

1.) this programme gets its input a line at a time. it copies all the
lines (full input) into a characters array.

2.) we then call a function "remove_comments" which removes all the
comments from the input.

3.) we then print the "array" which now does not contain any comments.

*/


#include<stdio.h>

#define MAXLENGTH 30000

int getline(char arr[]);
void remove_comments(char arr[]);

int main()
{
int i = 0;
char arr[MAXLENGTH];

/* initialising array */
for(i = 0; i < MAXLENGTH - 1; ++i)
arr = 0;


while(getline(arr))
;

remove_comments(arr);
printf("-------------------------\n");
printf("%s\n", arr);

return 0;
}


int getline(char arr[])
{
int c = 0;
int i = 0;

for(i = 0; i < MAXLENGTH - 1 && (c = getchar()) != EOF && c != '\n';
++i)
arr = c;

if(c == '\n')
arr[i++] = '\n';

arr = '\0';

return i;
}

void remove_comments(char arr[])
{
int i = 0;
int j = 0;
int incomment = 0;
char arr2[MAXLENGTH -1];

for(i=0; i < MAXLENGTH - 1; ++i)
arr2 = 0;


for(i=0; arr != '\0'; ++i)
{
if(arr != '"')
{
if(arr == '/' && arr[i+1] == '*')
incomment = 1;
}


if(arr == '*' && arr[i+1] == '/' && arr[i+2] != '"')
incomment = 0;

if(incomment == 0)
arr2[j++] = arr;
}

arr2[j] = '\0';

for(i = 0; arr2 != '\0'; ++i)
arr = arr2;
}

----------- OUTPUT ----------------
[arch@voodo kr2]$ gcc -ansi -pedantic -Wall -Wextra -O ex_1-23.c
[arch@voodo kr2]$ ./a.out
like this
 
J

Jonas

arnuld said:
there are no compile-time errors or warning. it runs but it does not
do what it is supposed to.

WANTED: to print the "input C programme" with all comments removed.

GOT: does not print anything.

-------- PROGRAMME -----------
/* K&R2: exercise 1-23

STATEMENT:
write aprogramme to remove all comments from a C programme
dont forget to handle quoted strings and character constants properly.

METHOD:

1.) this programme gets its input a line at a time. it copies all the
lines (full input) into a characters array.

2.) we then call a function "remove_comments" which removes all the
comments from the input.

3.) we then print the "array" which now does not contain any comments.

*/


#include<stdio.h>

#define MAXLENGTH 30000

int getline(char arr[]);
void remove_comments(char arr[]);

int main()
{
int i = 0;
char arr[MAXLENGTH];

/* initialising array */
for(i = 0; i < MAXLENGTH - 1; ++i)
arr = 0;


while(getline(arr))
;
Click to expand...


Try inserting

printf("%s\n", arr);

here for debug purposes...

remove_comments(arr);
printf("-------------------------\n");
printf("%s\n", arr);

return 0;
}


int getline(char arr[])
{
int c = 0;
int i = 0;

for(i = 0; i < MAXLENGTH - 1 && (c = getchar()) != EOF && c != '\n';
++i)
arr = c;

if(c == '\n')
arr[i++] = '\n';

arr = '\0';

return i;
}

void remove_comments(char arr[])
{
int i = 0;
int j = 0;
int incomment = 0;
char arr2[MAXLENGTH -1];

for(i=0; i < MAXLENGTH - 1; ++i)
arr2 = 0;


for(i=0; arr != '\0'; ++i)
{
if(arr != '"')
{
if(arr == '/' && arr[i+1] == '*')
incomment = 1;
}


if(arr == '*' && arr[i+1] == '/' && arr[i+2] != '"')
incomment = 0;

if(incomment == 0)
arr2[j++] = arr;
}

arr2[j] = '\0';

for(i = 0; arr2 != '\0'; ++i)
arr = arr2;
}
Click to expand...


You need to think through the different states that you can be in when
parsing the text. You can be in- or outside a string, and in- or outside a
comment. Inside a string, you can't be inside a comment, and vice-versa. It
might help to write the function in pseudo-code before getting down to
details.
 
A

arnuld

Try inserting

printf("%s\n", arr);

here for debug purposes...
Click to expand...

i inserted it there and it prints the "arr" without any trouble.
You need to think through the different states that you can be in when
parsing the text. You can be in- or outside a string, and in- or outside a
comment. Inside a string, you can't be inside a comment, and vice-versa. It
might help to write the function in pseudo-code before getting down to
details.
Click to expand...

ok, here is the modified code which again does not work:

-------- PROGRAMME ---------
/* K&R2: exercise 1-23

STATEMENT:
write aprogramme to remove all comments from a C programme
dont forget to handle quoted strings and character constants properly.

METHOD:

1.) this programme gets its input a line at a time. it copies all the
lines (full input) into a characters array.

2.) we then call a function "remove_comments" which removes all the
comments from the input.

3.) we then print the "array" which now does not contain any comments.

*/


#include<stdio.h>

#define MAXLENGTH 30000

int getline(char arr[]);
void remove_comments(char arr[]);

int main()
{
int i = 0;
char arr[MAXLENGTH];

/* initialising array */
for(i = 0; i < MAXLENGTH - 1; ++i)
arr = 0;


while(getline(arr))
printf("%s\n", arr);

remove_comments(arr);
printf("-------------------------\n");
printf("%s\n", arr);

return 0;
}


int getline(char arr[])
{
int c = 0;
int i = 0;

for(i = 0; i < MAXLENGTH - 1 && (c = getchar()) != EOF && c != '\n';
++i)
arr = c;

if(c == '\n')
arr[i++] = '\n';

arr = '\0';

return i;
}

void remove_comments(char arr[])
{
int i = 0;
int j = 0;
int incomment = 0;
int inquote = 0;
char arr2[MAXLENGTH -1];

for(i=0; i < MAXLENGTH - 1; ++i)
arr2 = 0;


for(i=0; arr != '\0'; ++i)
{
if(arr == '"')
{
incomment = 0;

if(inquote == 1)
inquote = 0;
else
inquote = 1;
}

if(inquote == 0)
{
if(arr == '/' && arr[i+1] == '*')
incomment = 1;
else if (arr == '*' && arr[i+1] == '/')
incomment = 0;
}

if(incomment == 0)
arr2[j++] = arr;
}

arr2[j] = '\0';

for(i = 0; arr2 != '\0'; ++i)
arr = arr2;
}

-------- OUTPUT ---------
[arch@voodo kr2]$ gcc -ansi -pedantic -Wall -Wextra -O ex_1-23.c
[arch@voodo kr2]$ ./a.out
like this
like this

and this
and this

-------------------------

[arch@voodo kr2]$ ./a.out
"like this"
"like this"

/* print "this" */
/* print "this" */
 
F

Fred Kleinschmidt

arnuld said:
Try inserting

printf("%s\n", arr);

here for debug purposes...
Click to expand...

i inserted it there and it prints the "arr" without any trouble.
You need to think through the different states that you can be in when
parsing the text. You can be in- or outside a string, and in- or outside
a
comment. Inside a string, you can't be inside a comment, and vice-versa.
It
might help to write the function in pseudo-code before getting down to
details.
Click to expand...

ok, here is the modified code which again does not work:

-------- PROGRAMME ---------
/* K&R2: exercise 1-23

STATEMENT:
write aprogramme to remove all comments from a C programme
dont forget to handle quoted strings and character constants properly.

METHOD:

1.) this programme gets its input a line at a time. it copies all the
lines (full input) into a characters array.

2.) we then call a function "remove_comments" which removes all the
comments from the input.

3.) we then print the "array" which now does not contain any comments.

*/


#include<stdio.h>

#define MAXLENGTH 30000

int getline(char arr[]);
void remove_comments(char arr[]);

int main()
{
int i = 0;
char arr[MAXLENGTH];

/* initialising array */
for(i = 0; i < MAXLENGTH - 1; ++i)
arr = 0;


while(getline(arr))
printf("%s\n", arr);

remove_comments(arr);
printf("-------------------------\n");
printf("%s\n", arr);

return 0;
}


int getline(char arr[])
{
int c = 0;
int i = 0;

for(i = 0; i < MAXLENGTH - 1 && (c = getchar()) != EOF && c != '\n';
++i)
arr = c;

if(c == '\n')
arr[i++] = '\n';

arr = '\0';

return i;
}

void remove_comments(char arr[])
{
int i = 0;
int j = 0;
int incomment = 0;
int inquote = 0;
char arr2[MAXLENGTH -1];

for(i=0; i < MAXLENGTH - 1; ++i)
arr2 = 0;


for(i=0; arr != '\0'; ++i)
{
if(arr == '"')
{
incomment = 0;

if(inquote == 1)
inquote = 0;
else
inquote = 1;
}

if(inquote == 0)
{
if(arr == '/' && arr[i+1] == '*')
incomment = 1;
else if (arr == '*' && arr[i+1] == '/')
incomment = 0;
}

if(incomment == 0)
arr2[j++] = arr;
}

arr2[j] = '\0';

for(i = 0; arr2 != '\0'; ++i)
arr = arr2;
}

-------- OUTPUT ---------
[arch@voodo kr2]$ gcc -ansi -pedantic -Wall -Wextra -O ex_1-23.c
[arch@voodo kr2]$ ./a.out
like this
like this

and this
and this

-------------------------

[arch@voodo kr2]$ ./a.out
"like this"
"like this"

/* print "this" */
/* print "this" */
Click to expand...


You might want to try writing a very simple starter program
that removes comments assuming there are no quoted strings.
When you get that to work, modify it to handle "/*" and "*/ "that
are inside strings.

Also you will have to worry about things like this:
char *ptr = "This string has an embedded \" ";
 
T

Thad Smith

arnuld said:
there are no compile-time errors or warning. it runs but it does not
do what it is supposed to.

WANTED: to print the "input C programme" with all comments removed.

GOT: does not print anything.

-------- PROGRAMME -----------
/* K&R2: exercise 1-23

STATEMENT:
write aprogramme to remove all comments from a C programme
dont forget to handle quoted strings and character constants properly.

METHOD:

1.) this programme gets its input a line at a time. it copies all the
lines (full input) into a characters array.

2.) we then call a function "remove_comments" which removes all the
comments from the input.

3.) we then print the "array" which now does not contain any comments.

*/


#include<stdio.h>

#define MAXLENGTH 30000

int getline(char arr[]);
void remove_comments(char arr[]);

int main()
{
int i = 0;
char arr[MAXLENGTH];

/* initialising array */
for(i = 0; i < MAXLENGTH - 1; ++i)
arr = 0;


while(getline(arr))
;

remove_comments(arr);
printf("-------------------------\n");
printf("%s\n", arr);

return 0;
}


int getline(char arr[])
{
int c = 0;
int i = 0;

for(i = 0; i < MAXLENGTH - 1 && (c = getchar()) != EOF && c != '\n';
++i)
arr = c;

if(c == '\n')
arr[i++] = '\n';

arr = '\0';

return i;
}

void remove_comments(char arr[])
{
int i = 0;
int j = 0;
int incomment = 0;
char arr2[MAXLENGTH -1];

for(i=0; i < MAXLENGTH - 1; ++i)
arr2 = 0;


for(i=0; arr != '\0'; ++i)
{
if(arr != '"')
{
if(arr == '/' && arr[i+1] == '*')
incomment = 1;
}


if(arr == '*' && arr[i+1] == '/' && arr[i+2] != '"')
incomment = 0;

if(incomment == 0)
arr2[j++] = arr;
}

arr2[j] = '\0';

for(i = 0; arr2 != '\0'; ++i)
arr = arr2;
}
Click to expand...


Assuming the first line is 10 characters long, where are you putting the
second line of input?
 
A

arnuld

You might want to try writing a very simple starter program
that removes comments assuming there are no quoted strings.
When you get that to work, modify it to handle "/*" and "*/ "that
are inside strings.
Click to expand...

OK, 1st a programme which does not take "quotes" into account. here
it is, it runs fine. i even gave it a C programme as input and it
removed the comments:

---------- PROGRAMME ----------
/* a programme that removes comments which are outside of quotes */

#include<stdio.h>

#define MAXLENGTH 10000

void remove_comments(char arr[]);

int main()
{
int c = 0;
int i =0;
char collect_input[MAXLENGTH];

while((c = getchar()) != EOF)
collect_input[i++] = c;

collect_input = '\0';

remove_comments(collect_input);
printf("----------------------\n%s\n", collect_input);

return 0;
}


void remove_comments(char arr[])
{
int i = 0;
int j = 0;
int incomment = 0;
char arr2[MAXLENGTH];

for(i = 0; arr != '\0'; ++i)
{
if(arr == '/' && arr[i+1] == '*')
incomment = 1;

else if(arr == '*' && arr[i+1] == '/')
incomment = 0;

if(incomment == 0 && arr == '*')
{
i = i + 2;
arr2[j++] = arr;
}

else if(incomment == 0)
arr2[j++] = arr;
}

arr2[j] = '\0';

i = 0;
while((arr = arr2[i++]) != '\0')
;
}

--------- OUTPUT ----------
[arch@voodo kr2]$ ./a.out
like this
and this is a /* comment */ not
----------------------
like this
and this is a not

[arch@voodo kr2]$
Also you will have to worry about things like this:
char *ptr = "This string has an embedded \" ";
Click to expand...

one more "if" statement, i guess, but 1st i need to modify my new
programme to handle quoted strings.
 
A

arnuld

You might want to try writing a very simple starter program
that removes comments assuming there are no quoted strings.
When you get that to work, modify it to handle "/*" and "*/ "that
are inside strings.
Click to expand...

i have modified my programme to remove quotes from C programme. it
TAKES CARE of quotes without any trouble. look down here for code and
output.
Also you will have to worry about things like this:
char *ptr = "This string has an embedded \" ";
Click to expand...


Hmm... this is the only POINT where that i am not able to think of
"How to check for this". i will give it a shot, after taking some
rest.

------ PROGRAMME ---------
/* a programme that removes comments which are outside of quotes */

#include<stdio.h>

#define MAXLENGTH 10000

void remove_comments(char arr[]);

int main()
{
int c = 0;
int i =0;
char collect_input[MAXLENGTH];

while((c = getchar()) != EOF)
collect_input[i++] = c;

collect_input = '\0';

remove_comments(collect_input);
printf("----------------------\n%s\n", collect_input);

return 0;
}


void remove_comments(char arr[])
{
int i = 0;
int j = 0;
int incomment = 0;
int inquote = 0;
char arr2[MAXLENGTH];

for(i = 0; arr != '\0'; ++i)
{
if(arr == '"')
{
if(inquote == 1)
inquote = 0;
else
{
inquote = 1;
incomment = 0;
}
}

else if(arr == '/' && arr[i+1] == '*' && inquote == 0)
incomment = 1;

else if(arr == '*' && arr[i+1] == '/' && inquote == 0)
incomment = 0;


if(incomment == 0 && inquote == 0 && arr == '*')
{
i = i + 2;
arr2[j++] = arr;
}
else if(inquote == 0 && arr == '"')
arr2[j++] = arr;
else if(incomment == 0)
arr2[j++] = arr;
}

arr2[j] = '\0';

i = 0;
while((arr = arr2[i++]) != '\0')
;
}

--------- OUTPUT ---------
[arch@voodo kr2]$ gcc -ansi -Wall -Wextra -pedantic -O new.c
[arch@voodo kr2]$ ./a.out
like "quote"
 
A

arnuld

You might want to try writing a very simple starter program
that removes comments assuming there are no quoted strings.
When you get that to work, modify it to handle "/*" and "*/ "that
are inside strings.

Also you will have to worry about things like this:
char *ptr = "This string has an embedded \" ";
Click to expand...

OK, after 2 hours of gruelling work, i did that :)

-------- PROGRAMME ----------
/* a programme that removes comments which are outside of quotes */

#include<stdio.h>

#define MAXLENGTH 10000

void remove_comments(char arr[]);

int main()
{
int c = 0;
int i =0;
char collect_input[MAXLENGTH];

while((c = getchar()) != EOF)
collect_input[i++] = c;

collect_input = '\0';

remove_comments(collect_input);
printf("----------------------\n%s\n", collect_input);

return 0;
}


void remove_comments(char arr[])
{
int i = 0;
int j = 0;
int incomment = 0;
int inquote = 0;
char arr2[MAXLENGTH];

for(i = 0; arr != '\0'; ++i)
{
if(arr == '"')
{
if(arr[i - 1] == '\\')
inquote = 1;
else if(inquote == 1)
inquote = 0;
else
{
inquote = 1;
incomment = 0;
}
}


else if(arr == '/' && arr[i+1] == '*' && inquote == 0)
incomment = 1;

else if(arr == '*' && arr[i+1] == '/' && inquote == 0)
incomment = 0;


if(incomment == 0 && inquote == 0 && arr == '*')
{
i = i + 2;
arr2[j++] = arr;
}
else if(inquote == 0 && arr == '"')
arr2[j++] = arr;
else if(incomment == 0)
arr2[j++] = arr;
}

arr2[j] = '\0';

i = 0;
while((arr = arr2[i++]) != '\0')
;
}

--------- OUTPUT -----------
[arch@voodo kr2]$ gcc -ansi -Wall -Wextra -pedantic -O new.c
[arch@voodo kr2]$ ./a.out
like "this" /* comment */ and
----------------------
like "this" and

[arch@voodo kr2]$ ./a.out
like "/*" done
----------------------
like "/*" done

[arch@voodo kr2]$ ./a.out
like "\" /*" and /* comment */ done
----------------------
like "\" /*" and done

[arch@voodo kr2]$ ./a.out
like "\" and /* inside quote comment */" what about /* this */ done
"*/" do
 
B

Barry Schwarz

ok, here is the modified code which again does not work:
-------- PROGRAMME ---------
/* K&R2: exercise 1-23

STATEMENT:
write aprogramme to remove all comments from a C programme
dont forget to handle quoted strings and character constants properly.

METHOD:

1.) this programme gets its input a line at a time. it copies all the
lines (full input) into a characters array.

2.) we then call a function "remove_comments" which removes all the
comments from the input.

3.) we then print the "array" which now does not contain any comments.

*/


#include<stdio.h>

#define MAXLENGTH 30000

int getline(char arr[]);
void remove_comments(char arr[]);

int main()
{
int i = 0;
char arr[MAXLENGTH];

/* initialising array */
for(i = 0; i < MAXLENGTH - 1; ++i)
arr = 0;
Click to expand...


Is there some reason you chose to leave the last element of the array
uninitialized? (You have an unhealthy obsession with MAXLENGTH-1.)
while(getline(arr))
printf("%s\n", arr);
Click to expand...

Don't you think you should process the data in arr before you loop
back?
remove_comments(arr);
printf("-------------------------\n");
printf("%s\n", arr);

return 0;
}


int getline(char arr[])
{
int c = 0;
int i = 0;

for(i = 0; i < MAXLENGTH - 1 && (c = getchar()) != EOF && c != '\n';
++i)
arr = c;

if(c == '\n')
arr[i++] = '\n';
Click to expand...


Why are you putting a \n at the end of your string?
arr = '\0';
Click to expand...


What happens if the user enter MAXLENGTH characters?
return i;
}

void remove_comments(char arr[])
{
int i = 0;
int j = 0;
int incomment = 0;
int inquote = 0;
char arr2[MAXLENGTH -1];

for(i=0; i < MAXLENGTH - 1; ++i)
arr2 = 0;


for(i=0; arr != '\0'; ++i)
{
if(arr == '"')
Click to expand...


What happens if the quote is inside a comment?
{
incomment = 0;

if(inquote == 1)
inquote = 0;
else
inquote = 1;
}

if(inquote == 0)
{
if(arr == '/' && arr[i+1] == '*')
incomment = 1;
else if (arr == '*' && arr[i+1] == '/')
incomment = 0;
Click to expand...


At this point you also need to skip over the */ or ...
}

if(incomment == 0)
arr2[j++] = arr;
Click to expand...


This will copy the two characters that terminate the comment into the
output.
}

arr2[j] = '\0';

for(i = 0; arr2 != '\0'; ++i)
arr = arr2;
Click to expand...


The output string is probably shorter than the input string, it would
be a good idea to terminate it.
}
Click to expand...

You really should invest in a debugger if you are not willing to desk
check your code.


Remove del for email
 
B

Barry Schwarz

OK, 1st a programme which does not take "quotes" into account. here
it is, it runs fine. i even gave it a C programme as input and it
Click to expand...

Only for a strange definition of fine.
removed the comments:

---------- PROGRAMME ----------
/* a programme that removes comments which are outside of quotes */

#include<stdio.h>

#define MAXLENGTH 10000

void remove_comments(char arr[]);

int main()
{
int c = 0;
int i =0;
char collect_input[MAXLENGTH];

while((c = getchar()) != EOF)
Click to expand...

Most terminal input is terminated with ENTER.
collect_input[i++] = c;

collect_input = '\0';

remove_comments(collect_input);
printf("----------------------\n%s\n", collect_input);

return 0;
}


void remove_comments(char arr[])
{
int i = 0;
int j = 0;
int incomment = 0;
char arr2[MAXLENGTH];

for(i = 0; arr != '\0'; ++i)
{
if(arr == '/' && arr[i+1] == '*')
incomment = 1;

else if(arr == '*' && arr[i+1] == '/')
incomment = 0;

if(incomment == 0 && arr == '*')
Click to expand...


What will happen to the input statement
x = a*b;
{
i = i + 2;
arr2[j++] = arr;
}

else if(incomment == 0)
arr2[j++] = arr;
}

arr2[j] = '\0';

i = 0;
while((arr = arr2[i++]) != '\0')
;
}

--------- OUTPUT ----------
[arch@voodo kr2]$ ./a.out
like this
and this is a /* comment */ not
----------------------
like this
and this is a not

[arch@voodo kr2]$
Also you will have to worry about things like this:
char *ptr = "This string has an embedded \" ";
Click to expand...

one more "if" statement, i guess, but 1st i need to modify my new
programme to handle quoted strings.
Click to expand...



Remove del for email
 
B

Barry Schwarz

i have modified my programme to remove quotes from C programme. it
TAKES CARE of quotes without any trouble. look down here for code and
output.

------ PROGRAMME ---------
/* a programme that removes comments which are outside of quotes */

#include<stdio.h>

#define MAXLENGTH 10000

void remove_comments(char arr[]);

int main()
{
int c = 0;
int i =0;
char collect_input[MAXLENGTH];

while((c = getchar()) != EOF)
collect_input[i++] = c;

collect_input = '\0';

remove_comments(collect_input);
printf("----------------------\n%s\n", collect_input);

return 0;
}


void remove_comments(char arr[])
{
int i = 0;
int j = 0;
int incomment = 0;
int inquote = 0;
char arr2[MAXLENGTH];

for(i = 0; arr != '\0'; ++i)
{
if(arr == '"')
{
if(inquote == 1)
inquote = 0;
else
{
inquote = 1;
incomment = 0;
}
}

else if(arr == '/' && arr[i+1] == '*' && inquote == 0)
incomment = 1;

else if(arr == '*' && arr[i+1] == '/' && inquote == 0)
incomment = 0;


if(incomment == 0 && inquote == 0 && arr == '*')
{
i = i + 2;
arr2[j++] = arr;
}
Click to expand...


What will this do to the statement
x = a*b;
else if(inquote == 0 && arr == '"')
arr2[j++] = arr;
else if(incomment == 0)
arr2[j++] = arr;
}

arr2[j] = '\0';

i = 0;
while((arr = arr2[i++]) != '\0')
Click to expand...


This invokes undefined behavior.
;
}

--------- OUTPUT ---------
[arch@voodo kr2]$ gcc -ansi -Wall -Wextra -pedantic -O new.c
[arch@voodo kr2]$ ./a.out
like "quote"
----------------------
like "quote"

[arch@voodo kr2]$ ./a.out
like "quote" /* comment */ out of comment
----------------------
like "quote" out of comment

[arch@voodo kr2]$ ./a.out
like "/* inside quote */" and /*outsaide quote */ DONE
Click to expand...


Remove del for email
 
B

Barry Schwarz

OK, after 2 hours of gruelling work, i did that :)

-------- PROGRAMME ----------
/* a programme that removes comments which are outside of quotes */

#include<stdio.h>

#define MAXLENGTH 10000

void remove_comments(char arr[]);

int main()
{
int c = 0;
int i =0;
char collect_input[MAXLENGTH];

while((c = getchar()) != EOF)
collect_input[i++] = c;

collect_input = '\0';

remove_comments(collect_input);
printf("----------------------\n%s\n", collect_input);

return 0;
}


void remove_comments(char arr[])
{
int i = 0;
int j = 0;
int incomment = 0;
int inquote = 0;
char arr2[MAXLENGTH];

for(i = 0; arr != '\0'; ++i)
{
if(arr == '"')
{
if(arr[i - 1] == '\\')
Click to expand...


At this point, you don't know if arr[i-1] exists?
inquote = 1;
else if(inquote == 1)
inquote = 0;
else
{
inquote = 1;
incomment = 0;
Click to expand...

What will this do to the statement
x = a+b; /* compute "total" */
}
}


else if(arr == '/' && arr[i+1] == '*' && inquote == 0)
incomment = 1;

else if(arr == '*' && arr[i+1] == '/' && inquote == 0)
incomment = 0;


if(incomment == 0 && inquote == 0 && arr == '*')
{
i = i + 2;
arr2[j++] = arr;
}
Click to expand...


What will this do to the statement
x = a*b;
else if(inquote == 0 && arr == '"')
arr2[j++] = arr;
else if(incomment == 0)
arr2[j++] = arr;
}

arr2[j] = '\0';

i = 0;
while((arr = arr2[i++]) != '\0')
Click to expand...


This invokes undefined behavior.
;
}
Click to expand...

You ought to let the dust settle on one program (at least a day or
two) until so you can fix all its problems before running off to do
another. The last three in this thread have several problems in
common.


Remove del for email
 
J

Jonas

arnuld said:
On Apr 6, 11:40 pm, "Fred Kleinschmidt" <[email protected]>
wrote:

You might want to try writing a very simple starter program
that removes comments assuming there are no quoted strings.
When you get that to work, modify it to handle "/*" and "*/ "that
are inside strings.

Also you will have to worry about things like this:
char *ptr = "This string has an embedded \" ";
Click to expand...

OK, after 2 hours of gruelling work, i did that :)

-------- PROGRAMME ----------
/* a programme that removes comments which are outside of quotes */

#include<stdio.h>

#define MAXLENGTH 10000

void remove_comments(char arr[]);

int main()
{
int c = 0;
int i =0;
char collect_input[MAXLENGTH];

while((c = getchar()) != EOF)
collect_input[i++] = c;

collect_input = '\0';

remove_comments(collect_input);
printf("----------------------\n%s\n", collect_input);

return 0;
}


void remove_comments(char arr[])
{
int i = 0;
int j = 0;
int incomment = 0;
int inquote = 0;
char arr2[MAXLENGTH];

for(i = 0; arr != '\0'; ++i)
{
if(arr == '"')
Click to expand...


If we are inside a comment, we don't care if we're entering a quote or not.
/* "haha */ is just as valid a comment as /* "haha" */ or /* haha */.
{
if(arr[i - 1] == '\\')
Click to expand...

If i == 0, you're looking at arr[-1].
inquote = 1;
else if(inquote == 1)
inquote = 0;
else
{
inquote = 1;
incomment = 0;
Click to expand...

entering or leaving a quoted string does not affect whether or not we're in
a comment.
}
}


else if(arr == '/' && arr[i+1] == '*' && inquote == 0)
incomment = 1;

else if(arr == '*' && arr[i+1] == '/' && inquote == 0)
incomment = 0;


if(incomment == 0 && inquote == 0 && arr == '*')
{
i = i + 2;
arr2[j++] = arr;
}
else if(inquote == 0 && arr == '"')
arr2[j++] = arr;
else if(incomment == 0)
arr2[j++] = arr;
}

arr2[j] = '\0';

i = 0;
while((arr = arr2[i++]) != '\0')
;
}
Click to expand...



The C language aside, it would probably help to look at the algorithm that
the function implements, and separate that from implementation details like
handling arrays in C.
 

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