Are there other string classes?

Hi, I'm getting pretty sick of char * and all other things C++ fail with when I need to type in and store some text. All I want is no extra characters. No flushing buffers, cin.ignore() and things. No keeping track of what works when, ever! However, I do need to be able to convert back to c-strings because i use the strings with winsock-functions like send and recv.

So are there any classes that succeed with the complicated task of reading user input and storing it in an unchanged form?

PS the built in sring-class sucks too

So, then the question becomes, what's wrong with the built-in string class? It sounds like all your problems are input-related, which means you should probably be using more better input commands, like getline, instead of trying to use <<.

Code:

---

std::string line;
std::getline(std::cin, line);

---

No extra characters. No flushing buffers.
You will not be able to escape keeping track of if it worked or not, however.
Also supports converting it back to a C-style string.

If you need a specific type of data, then I have posted an input class on the board that pretty much handles it all for you.

Quote:

---

Originally Posted by tabstop

So, then the question becomes, what's wrong with the built-in string class? It sounds like all your problems are input-related, which means you should probably be using more better input commands, like getline, instead of trying to use <<.

---

I've used all there is. Sometimes one method works, sometimes another does. Sometimes I have to add cin.ignore() here and there, sometimes i don't need too. Thing is, I don't want to be forced to keep track of this anymore. I want one function read(mystring); that reads from my keyboard to mystring until I hit enter. And it would be nice if it worked flawlessly every time.

On the other hand, getline can only go bad if it reads end-of-file, I believe (or some complete input disaster happens), not just because the input doesn't match some format or other. I'm often a bad person and don't check whether getline fails.

Elysia, ok that works. But not always when used mixed with cin.get(). Maybe I've blamed the string-class because cin.get screws it up.

Yes, it is. Best not to mix them, or you will run into the same problem again.

It seems to me that std::geline and cin.get() get along just fine. It's operator>> that's guilty of leaving stuff into the buffer (I guess that has some purpose though, so you can for example see what the delimiter was).

Well, get also leaves the delimiting character in the buffer too (hence all the calls to .ignore).

Ah yes, my bad.

In any case you don't need a new class. Perhaps wrapping the input functions up in functions that automatically clean the buffer is enough?

Quote:

---

Originally Posted by tabstop

So, then the question becomes, what's wrong with the built-in string class?

---

It is a monolithic class :p

(Though technically it is not "built-in" since it is part of the standard library, not the core language, but anyway finnepower did not have Herb Sutter's view in mind with that comment.)

Quote:

---

Originally Posted by anon

Perhaps wrapping the input functions up in functions that automatically clean the buffer is enough?

---

Yes, that sounds like a viable approach to me. Simply not mixing formatted input functions with get() and getline() is not always the best solution, in my opinion, since on occasion you may want to use both.

You are wise, laserlight.

It often seems like guesswork to me as to when I'll need an ignore(). Does this always blast past the user?

Code:

---

std::cin >> type; //user makes a '\n' to indicate entry
cin.get(); //maybe the buffer is empty and we'll wait... maybe there's an extra \n and we won't?

---

For me, cin consistently leaves the delim in the stream. I can't seem to find the sentence in Stroustrup that clarifies this.

The only legitimate way I can think of, using >>, to possibly not have a \n character left over is to set noskipws and read in a single character. But \n is not considered a valid part of any of the primitive datatypes (except char, and then only when noskipws is set) so it will be left in the input stream.

Quote:

---

Originally Posted by CodeMonkey

It often seems like guesswork to me as to when I'll need an ignore(). Does this always blast past the user?

---

What happens if the user input has trailing whitespace? One way is to simply ignore as many characters as possible that may be left in the buffer until and including the next newline character:

Code:

---

std::cin >> type;
std::cin.ignore(std::numeric_limits<std::streamsize>::max(), '\n');

---

Another way is to specifically extract and discard whitespace:

Code:

---

std::cin >> type;
std::cin >> std::ws;

---

Code:

---

std::cin >> type;

---

My input class performs this beautifully without the need to worry for cleaning the input.
So if that sort of thing is what you need, I may have the solution wrapped inside a class, which I posted some time ago.

There are several common issues with using cin and probably quite a few more that aren't common.

For example, if you don't need to handle bad input, then you can get away with always calling cin.ignore() after calls to cin >> to ignore the trailing newline.

If you do want to handle error conditions, then something like this usually works:

Code:

---

// prompt here

while (!(cin >> data) || cin.get() != '\n')
{
  cin.clear();
  cin.ignore(numeric_limits<streamsize>::max(), '\n');

  // error message and re-prompt here
}

---

Both those solutions allow mixing of cin >> and getline.

If you want it all encapsulated in some functions, see this post:

http://cboard.cprogramming.com/showp...4&postcount=24

I don't understand the griping about how hard it is to do a certain thing. Is reading a single line of input hard? Maybe for some people -- I don't really think so -- but whether it's hard or not, why not just get it right once, throw it in your personal library "bag of tricks" and forget about it.

Sure, sometimes stuff is "hard." So write the code and then never write it again.

Quote:

---

Originally Posted by brewbuck

Sure, sometimes stuff is "hard." So write the code and then never write it again.

---

I agree, except that once you've gained another year or five of experience, you can usually come up with a better way to solve the same problem.

--
Mats

Perhaps it is more of a lot of code to do such an easy and common thing. Having to repeat all that code can be tiring. There is "standard" solution available out of the box.

Quote:

---

Originally Posted by Elysia

Code:

---

std::cin >> type;

---

My input class performs this beautifully without the need to worry for cleaning the input.
So if that sort of thing is what you need, I may have the solution wrapped inside a class, which I posted some time ago.

---

So does cin evidently.

I thought we all agreed that class you made suffered from feature creep and the better solution was a collection of free functions.

No, you rejected the newer features, which I took under advisement, but not the latest working version I posted.

So where can this function be found?

It is a class I had made and I wish I knew. I do not have its address an I cannot search for it.

Well, if you want to read user input, until an enter is pressed, and just not want to worry about something going bad, then you can use something like this. Note that this isn't to use exactly how it is, it is just a quick possibly non-working example

Code:

---

bool getlineSafe (istream& is, string& str)
{
        try
        {
              getline(is, str);
              return true;
        }
        catch()
        {
              return false;
        }
}

---

If an error occurs you can handle it as you want. Or you can use another method rather than try/catch. The point is that if an error occurs you will need to handle it or ignore it. You don't really have another option.

Personally I use the simplest function, like get() to get one by one characters and do exactly what I want. Wrap it in a class/function with some parameters and not worry about it again

I do not know if an empty catch works, though. Does it?

Quote:

---

Originally Posted by C_ntua

Well, if you want to read user input, until an enter is pressed, and just not want to worry about something going bad, then you can use something like this.

---

That is not very useful though. By default, std::getline() would not throw an exception due to an I/O error. One might as well just use the return value of std::getline() since it is indirectly convertible to bool.

Quote:

---

Originally Posted by Elysia

I do not know if an empty catch works, though. Does it?

---

I believe it is a syntax error, but that was just an example anyway.

The number of replies confirm the complexity of this. And impatient as i am, I'm moving to Python instead. I never need the low level benefits of C++ anyway.

Quote:

---

Originally Posted by finnepower

The number of replies confirm the complexity of this.

---

That is a rather naive measure: some of the replies are merely comments that the process is easier than what some people make it out to be.

Quote:

---

Originally Posted by finnepower

And impatient as i am, I'm moving to Python instead. I never need the low level benefits of C++ anyway.

---

On the other hand, if you can get away with using a higher level language like Python (e.g., your program is I/O intensive rather than CPU intensive), it is usually a good idea to use that instead.