C++ how to ignore comments "//" in line count!

[legcramp]

while(getline(infile,lines)) 
	{

		if(lines.empty())  
			{
				continue;
					
			}
		if(lines.find("//") == true)
			{
				continue;
			}
		
		++linecount;

I got the counter to skip spaces flawlessly, but skipping the comments in the line count isn't going very well.

Any help is appreciated!

 

[Markbnj]

Hmm, don't see anything obviously wrong, but in general you haven't given enough information to enable someone to help. What erroneous behavior or results are you seeing?

 

[legcramp]

Sorry, forgot to mention that I just want the counter to skip the line if the "//" is in front of the line.

Right now, the line is skipped for example:

cout << "Hello World" << endl; //comment here


But I only want it to skip the line if:

//comment here ...........

 

[BoT]

why would you want to do that? it is editor dependent not code dependent. there is nothing in C#, C+ or C++ that would make the editor skip count. it's an interpretation of the editor of how to present what you wrote in code.

 

[Merad]

You're ignoring the line if // appears anywhere in it. Instead of searching the whole string you need to see if it begins with //. Ideally, strip whitespace from the start of the string before checking.

Also, assuming what you posted is actual code, you're using the find method incorrectly: http://www.cplusplus.com/reference/string/string/find/

 

[Ken g6]

http://stackoverflow.com/questions/2394017/remove-comments-from-c-c-code

 

[purbeast0]

string:find does not return a boolean. that is why it's never gets inside of that second conditional. it returns the index of where it finds the parameter inside of the string.

you're basically comparing an integer == true.

make it compare to -1 (which it returns if it finds nothing) instead of true.

 

[Crusty]

string:find does not return a boolean. that is why it's never gets inside of that second conditional. it returns the index of where it finds the parameter inside of the string.

you're basically comparing an integer == true.

make it compare to -1 (which it returns if it finds nothing) instead of true.

Well, really you should use string::npos to compare against.

 

[purbeast0]

Well, really you should use string::npos to compare against.

been forever since i've done c++ so sorry if i missed that 🙂

i was just going off of my general knowledge of when doing finds on strings in general, it always returns the index if it finds it and -1 if it finds nothing.

 

[mjd]

That code isn't going to skip non-empty blank lines either.
Suppose your example data has a blank line with spaces or tabs or other whitespace in it!

 

[DaveSimmons]

That code isn't going to skip non-empty blank lines either.
Suppose your example data has a blank line with spaces or tabs or other whitespace in it!

Good point. A simple approach would be:

for each line,
- strip leading whitespace
- skip if the stripped string empty or the first 2 characters are "//"

This won't work for /* ... */ blocks of course, but that probably isn't asked for in the homework.

 

[mjd]

Yeah, there are a bunch of ways to solve this problem. And it really depends on the intent of the homework question and tools available.

character-level string processing,
Boost style trim and matching,
C++11 regex module use,
or more!

 

[Crusty]

Yeah, there are a bunch of ways to solve this problem. And it really depends on the intent of the homework question and tools available.

character-level string processing,
Boost style trim and matching,
C++11 regex module use,
or more!

Does that work in G++ yet?

Last time I tried to use it, everything compiled and linked just fine, but the library just returned completely bogus results. Turns out the version of G++ I had didn't support it yet 🙁

 

[mjd]

Does that work in G++ yet?

Last time I tried to use it, everything compiled and linked just fine, but the library just returned completely bogus results. Turns out the version of G++ I had didn't support it yet 🙁

A cursory glance at the internet tells me that g++ regex is still broken as of December 2013. I haven't tried it myself.

 

[MrScott81]

Here's how I would do it in java:

String line=null;
int linescount=0;
while( (line = in.readLine()) != null)
{
  if(line.trim().equals("") || line.trim().startsWith("//"))
    continue;
  linescount++;
}