Thread: preprocessor program

Code:

//a program which works as a preprocess removes comments in a given program

#include<stdio.h>
main()
{
int i,start,end;
char array[500],c;
        for(i=0;(c=getchar())!=EOF;i++)
        array[i]=c;
        for(i=0;array[i]!=EOF;i++)
        {
                if( (array[i]=='/') && (array[i+1]=='*') )
                        start=i;
                if( (array[i]=='*') && array[i+1]=='/')
                {
                end=i+1;
                for(i=start;i<=end;i++)
                array[i]='\b';
                }
        }
        //for(i=start;i<=end;i++)
        //      array[i]='\0';
        printf("after comments removal the text is as below\n");
        for(i=0;array[i]!=EOF;i++)
                putchar(array[i]);
        printf("\n");
}

here i have created a demo code which works similar to a pre processor which removes the comments in the given program but this is yielding nasty results debug my program please
INPUT to program:

Code:

/*comment1*/
statement1;
/*comment2*/

statement2;
/*comment3*/
statement3;

OUTPUT:

Code:

after comments removal the text is as below

statement1;


statement2;

statement3;�q*Дq�$Дq�@(u�q@

im supposed to remove the comments BUT THE BLANK SPACES REMAIN HOW TO REMOVE THEM???
also i get unwanted character at the end ,what changes can i do to my program

moreover here i want to give a .c file as input to program how could i do that in linux
can i try code.c | ./program

One idea is to recognise two states: within a comment and not in a comment. So, while the state is "within a comment", you simply discard every character until you encounter a "*", upon which you do a lookahead for "/". If the next character is indeed a "/", you change the state (if there is no next character, then the content is invalid). While the state is "not in a comment", you store the character in the array, except that when you encounter a "/", you do a lookahead and only store the character if the next character is not a "*". If it is, you discard both characters and change the state, otherwise you store both characters (or just "/", if that is the last character).

Now, since you read the entire content into an array first, "discarding" a character is a matter of maintaining two pointers: a read pointer and a store pointer. "Discard" means advancing the read pointer without advancing the store pointer.

Originally Posted by shyam.sunder91

also i get unwanted character at the end

You should always, always initialize your variables and then this problem should go away.

And while I'm at it, you should indent properly, always use braces with if/for/while/do blocks, you should have an int main and return from it and use a little more whitespace to make your program easier to read.