Comment Stripper

[Sky Diploma]

Here is a comment stripper program from which takes input from Cin and removes the comments.

#include <iostream>
#include <fstream>

char Getchar();
char var;
int main()
{
	char ch;
	do
	{
		Getchar();
		switch(var)
		{
			case '/':
			switch(Getchar())
			{
				case '*':
					Getchar();
					while(true)
					{
						if(var=='*'&&Getchar()=='/')
						{
							break;
						}
						else
						{
							Getchar();
						}
					}
					break;

				case '/':
					while(Getchar()!='\n');
					std::cout<<'\n';
					break;

				default:
					break;
	
			}
			break;
			case '"':
			do
			{
				std::cout<<var;	
			}
			while (Getchar()!='"');
			std::cout<<var;
			break;

			default:
			std::cout<<var;
		}
			
	}
	while(var!='x');
	
}

char Getchar()
{
	 std::cin.get(var);
	 return var;
}

So any improvements ?
Secondly I am looking for another way by which i can close input any suggestions on that.
I mean this program exits when "x" is inputted. Is there any other way of Exiting?

[Ancient Dragon]

Oh, so all it does is strip comments from keyboard input and not from a *.c or *.cpp data file??? Why would you want to write such a program?

>>I mean this program exits when "x" is inputted. Is there any other way of Exiting?

Just press Ctrl+C.

[Sky Diploma]

Oh, so all it does is strip comments from keyboard input and not from a *.c or *.cpp data file??? Why would you want to write such a program?

>>I mean this program exits when "x" is inputted. Is there any other way of Exiting?

Just press Ctrl+C.

Wouldnt I be Able To Replace cin and cout with filestreams and remove comments from .c or .cpp files

This is an exercise in my c++ book so I just wrote it down. As I am teaching myself C++ i post down the code and ask you guys for improvements :)

What does CTRL+C do?

[ArkM]

Improvements? Try to process this (correct) line in C++ and see what happens:

ifstream file("//please/dont/strip.me");

;)

[Sky Diploma]

Improvements? Try to process this (correct) line in C++ and see what happens:

ifstream file("//please/dont/strip.me");

;)

It returns

ifstream("//please/dont/strip.me");

[mvmalderen]

What does CTRL+C do?

CTRL+C just breaks/stops the execution of a console program :)

By the way: I had also expected your program was stripping comments from C/C++ source files, but you can easily adapt it to remove comments from files :)

[WaltP]

So any improvements ?

Yes. Stop using TABs to indent. Set your editor to use 4 SPACEs when the TAB key is pressed.

As for exiting, you can exit when ENTER is pressed all by itself.

And about Ctrl+C, look it up.

[ArkM]

It returns...

Oh, that damned tab indentation! ;)
OK, try this:

//\
strip me!

[Ancient Dragon]

Wouldnt I be Able To Replace cin and cout with filestreams and remove comments from .c or .cpp files

Actuall you don't have to change a thing to make it get input from a data file instead of the keyboard -- just direct stdin from data file, like this: c:>myprogram.exe <test.cpp <Return> When the above is typed from a command prompt window your program will get input from the file test.cpp instead of the keyboard.

[mvmalderen]

Actuall you don't have to change a thing to make it get input from a data file instead of the keyboard -- just direct stdin from data file, like this: c:>myprogram.exe <test.cpp <Return> When the above is typed from a command prompt window your program will get input from the file test.cpp instead of the keyboard.

But it won't strip the comments out of the file ...

[Ancient Dragon]

If you want the comments stripped from the file then just redirect stdout to another file c:>myprogram.exe <test.cpp >newfile.cpp <Return>

[Sky Diploma]

Thats really Nice to Know :)

Will that work on all platforms

Is this just like using Pipes to pass information

for example
WIndows.

C:> dir >>output.txt

Would put all the output of the Dir command In Output.txt

[mvmalderen]

Will that work on all platforms

I know that it works on Windows, Linux and Unix :P

for example
WIndows.

C:> dir >>output.txt

Would put all the output of the Dir command In Output.txt

Yes, but remember that >> is different from > : >> appends to the file (if it exists, otherwise it's just creating the file and writing the output of the dir command to it)

For further info on this: http://commandwindows.com/command1.htm

[ArkM]

Other failed tests:

f("\""); // Strip me!

ch = '\"'; // Strip me!

Probably, this is too much!(?) :

#if 0
/* Code wrecks...
#endif
cout << "Hello, Sky Diploma!\n";

To echo ArkM there are going to be a lot of exceptions.

The best/easiest way would be to use regular expressions via the boost library.

[ArkM]

To echo ArkM there are going to be a lot of exceptions.
The best/easiest way would be to use regular expressions via the boost library.

In no circumstances.
There are few syntax contexts where comments occured, so reduced scanner+parser tandem which is capable to strip comments is a very simple and fast code w/o (relatively) cumbersome and slow regex.
However it's not so easy to cope with macros...

[Sky Diploma]

I agree that I dint consider the /" .

And I

ch = '\"'; // Strip me!

And thought that that was invalid.
So i guess i will work on that as well :)

[ArkM]

Some additions:
>...to be a lot of exceptions.
Nope.
Essentially, Sky Diploma's code does not recognized correctly three very simple lexical-level constructs:
1. string literals
2. character literals
3. line continuation
Besides that it has a very strange termination condition (letter x - why?! ) and can't react to eof condition...

There are cases :

"Since comments can be embedded in strings, or look like function prototypes, care must be taken to ignore these cases. "
http://www.perl.com/doc/FAQs/FAQ/oldfaq-html/Q4.27.html

etc which would make this program very messy.

Regex is the ideal solution. But if you wish to prove me wrong please do.

[Sky Diploma]

#include <iostream>
#include <fstream>

char Getchar();
char var;
int main()
{
	do{
		Getchar();
		switch(var)
		{
			case '/':
			switch(Getchar())
			{
				case '*':
					Getchar();
					while(true)
					{
						if(var=='*'&&Getchar()=='/')
						{
							break;
						}
						else
						{
							Getchar();
						}
					}
					break;

				case '/':
					while(Getchar()!='\n');
					std::cout<<'\n';
					break;

				default:
					break;
	
			}
			break;
			case '\'':
			std::cout<<var;
			Getchar();
			do
			{
			if(var=='\\'&&Getchar()=='\'')
				{
				std::cout<<'\\';

				}
			std::cout<<var;
			}
			while (Getchar()!='\'');
			std::cout<<var;
			break;
			case '"':
			do
			{
				if(var=='\\'&&Getchar()=='"')
				{
				std::cout<<'\\';

				}
				std::cout<<var;
				Getchar();	
			}	while (var!='"');
			std::cout<<var;
			break;
			default:
			std::cout<<var;
		}
			
	}
	while(std::cin);
	
}

char Getchar()
{
	 std::cin.get(var);
	 return var;
}

This is like the improvised function.
However i still am not able to crack "\//" AND "/*................." Till end of file though.
Please Help me out with that .

Though I dint test it through a lot of Code. I Think that this would be enough. But would it?

[mvmalderen]

You could also use the following code to strip all the C++ style comments:

char expr[80]; // user inputted expression (with/without comments)
/* Strip down the '//'-comments */
char *p = strstr(expr, "//");
if(p) *p='\0';

expr now contains the expression without all the C++ comments :)

The C-style comments are a bit harder to do, but it's do-able :P

[Sky Diploma]

You could also use the following code to strip all the C++ style comments:

char expr[80]; // user inputted expression (with/without comments)
/* Strip down the '//'-comments */
char *p = strstr(expr, "//");
if(p) *p='\0';

expr now contains the expression without all the C++ comments :)

The C-style comments are a bit harder to do, but it's do-able :P

I dont think that this will work out.

string s="foldername//file";

The above function would remove the file"; part.

[mvmalderen]

I dont think that this will work out.

string s="foldername//file";

The above function would remove the file"; part.

True, but keep in mind that this way doesn't work directly with C++ strings :) (however with a few modifications you can make it also work for C++ strings :))