Alright, how does one compare an element of argv with a literal string?

How does one compare an element of argv (an array of char pointers) with a literal string, or to put it more accurately, how does one compare the char array being pointed at by an element of argv with a literal string?

When I use the syntax:

if (argv[1] == "ALiteralString")

my compiler warns "comparison with string literal results in unspecified behavior", and its right. Its unspecified behavior alright. Because it ignores the if statement designed to be entered if the second argument (counting the program name) is a certain string ("--help", to be more exact).

And if I try dereferencing the char pointer argv[1] in the if statement by doing

if (*argv[1] == "ALiteralString")

it wont compile at all. It says "ISO C++ forbids comparison between pointer and integer".

Ok, another problem dealing with argv:

When I get the argv[1] argument and store it in a string, I then get the size of the string by calling the size() function of that string.
Later on in the code, I was noticing it was outputting the wrong message at was supposed to be the last character of the string (i.e. inputFilePathSize - 1). And so I went and outputted the size of the inputFilePath string (which is the string which was given the contents of argv[1]), and it turns out that size is 2 less than what it should be.

It claims the length/size of the string is 32, when in reality, its 34. It also gets the size of argv[2] (an output filename string) wrong. It claims it has 7 characters, when in reality, it has 9.

With both strings, I depending on the size() function of the string type, and store what that function returns inside an int. Is that the problem? I know that string::size() returns a size_t type which is an unsigned type as opposed to "int" which is a signed type. I don't know if that would change the inner value though. I was under the impression it wouldn't, which is why I'm using an int variable instead of a size_t for storing the size.

Use strcmp() to compare strings.

Quote:

---

Originally Posted by Dino

Use strcmp() to compare strings.

---

Is that a member function of the string type?
I couldn't find it anywhere in the string C++ reference, though I see a "compare()" function which might do the same thing as the function you mentioned.

You're running into the fact that C++ supports two distinct but unrelated types which might be described as a string.

1) The std::string class which is specified in the header <string>.

2) An array of char that is delimited with a zero. This form of string is inherited by C++ from C.

String literals are stored in the second form. For example "Hello" is represented by 6 characters 'H', 'e', 'l', 'l', 'o', and '\0' (a zero character).

The argv argument of main() is an array of strings in the second form.

strcmp() is a function declared in the C header <string.h> or in the C++ header <cstring> (where the function is in namespace std). It is used to compare two strings that are each in the second form above.

The C++ std::string class has a constructor that accepts a const char * (so a C-style string can be converted to a std::string) and a method named c_str() which returns an equivalent C-style string.

Quote:

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Originally Posted by grumpy

You're running into the fact that C++ supports two distinct but unrelated types which might be described as a string.

1) The std::string class which is specified in the header <string>.

2) An array of char that is delimited with a zero. This form of string is inherited by C++ from C.

String literals are stored in the second form. For example "Hello" is represented by 6 characters 'H', 'e', 'l', 'l', 'o', and '\0' (a zero character).

The argv argument of main() is an array of strings in the second form.

---

That's right. So why then is:

if (argv[3] == "--help")

not working, since they're both c-style strings?

Quote:

---

strcmp() is a function declared in the C header <string.h> or in the C++ header <cstring> (where the function is in namespace std). It is used to compare two strings that are each in the second form above.

The C++ std::string class has a constructor that accepts a const char * (so a C-style string can be converted to a std::string) and a method named c_str() which returns an equivalent C-style string.

---

Right. A little Googling provided me that same info just a little before your reply.
Thanks to both of you for replying, btw.

I just tried to compare two c-style strings with strcmp(), passing in argv[3] as the first argument, and the c-style string "--help" as the second, and storing the int result in a variable which I then check inside an if statement to see if its 0 (meaning the two strings are the same). If they are, I print out a help message. Else if they're not, I output an error saying you can't pass in just 1 argument into the program, if that argument is not "--help". Only problem is, that else if statement is entered even though I DO pass in "--help" as the only argument (not counting the program name, of course), and so I end up getting that error which lets me know its f****** up for some reason.

argv[] elements will always point to c-style strings.

Show your current code that is not working.

If you are only passing 1 argument it is argv[1] not argv[3]. Also you can check the number of arguments passed by using argc (The number of parameters passed).

Quote:

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Originally Posted by jimblumberg

If you are only passing 1 argument it is argv[1] not argv[3]. Also you can check the number of arguments passed by using argc (The number of parameters passed).

---

Yes, I know that. I neglected to mention that I'm allowing the user to pass in the "--help" argument as either argv[1] when there is only one argument other than the program name OR argv[3] when the number of arguments other than the program name is 3. So both are valid. However, the statement that's acting up when I pass in only one argument which is "--help" looks like this:

Code:

---

if (argc == 2) {
            if (argv[1] == "--help") {
                cout<< "You passed the '--help' argument." <<endl;
                cout<< helpObject.help(); //print help message
                cout<< "\n\nPress Enter to end this program." <<endl;
                cin.get(); //make the user press Enter
                return 0; //to indicate successful program completion because user passed in the --help argument
            }

            else {
                cout<< "Error! If you only pass 1 argument, that cannot be\n"
                      "anything other than '--help' to print a help message." <<endl;
                cout<< helpObject.help(); //print help message
                cout<< "\n\nPress Enter to end this program." <<endl;
                cin.get(); //make the user press Enter
                return 1; //because the user tried to do something funny and unallowed with this program
            }
 }

---

The problem is, the "else" instead of the "if" statement is entered, even though I pass in "--help", and so consequently, the program outputs the wrong thing.
Also note that the code above is both what I tried first, and also is my current code, though I also tried using strcmp() as suggested instead of the '==' operator to compare the strings, but the result was the same, so I switched it back, since I prefer the compare statement to be in only 1 line.

You must use strcmp() to compare cstrings

Jim

Quote:

---

Originally Posted by Programmer_P

That's right. So why then is:

if (argv[3] == "--help")

not working, since they're both c-style strings?

---

Because what you've done here is a pointer comparison. It compares the address of the first character in argv[3] with the address of the first character in the string literal "--help". Since those addresses in memory will generally be different, the comparison yields a false (zero) result.

Quote:

---

Originally Posted by Programmer_P

I just tried to compare two c-style strings with strcmp(), passing in argv[3] as the first argument, and the c-style string "--help" as the second, and storing the int result in a variable which I then check inside an if statement to see if its 0 (meaning the two strings are the same). If they are, I print out a help message. Else if they're not, I output an error saying you can't pass in just 1 argument into the program, if that argument is not "--help". Only problem is, that else if statement is entered even though I DO pass in "--help" as the only argument (not counting the program name, of course), and so I end up getting that error which lets me know its f****** up for some reason.

---

Without seeing your code or the command line you're using to run your program, only guesses are possible. However, the problem is either in your code or in the command line you are providing to your program.

The obvious possibilities are

1) "--help" is not the third argument you are supplying after the program name, so the comparison is doomed to failure.

2) You're doing the comparison incorrectly. From your description, you could be doing;

Code:

---

  int result = strcmp(argv[3], "--help");
  if (result = 0)
        do_something();
  else
        do_something_else();

---

A single '=' character does an assignment. A comparison requires two of them. if (result = 0) will always test false (as zero is false).

3) You are using a command line interpreter that filters "--help", and changes what is being passed to your program. For example, conversion to upper case, stripping one of the '-' characters.

4) You have not ensured argv[3] is valid. You also need to check argc. For example, if argc is less than 4, using strcmp(argv[3], anything) always gives undefined behaviour.

Quote:

---

Originally Posted by jimblumberg

You must use strcmp() to compare cstrings

Jim

---

Hmm...though I thought I had tried that already, I just changed the code to use strcmp(), and this time, it works as expected. I think probably what happened before was I was accidentally editing the code which deals with the argv[3] and accepts the same argument as argv[1] and thinking I was editing the code which execution was entering when I passed "--help" as the only argument, but now I realize what was actually happening.

Oh well...problem solved. :)

Quote:

---

Originally Posted by grumpy

Because what you've done here is a pointer comparison. It compares the address of the first character in argv[3] with the address of the first character in the string literal "--help". Since those addresses in memory will generally be different, the comparison yields a false (zero) result.

---

Well, that is what I originally guessed was happening if I compare argv[3] with a literal string. However, when I attempted to dereference the pointer at element 3 of argv, it wouldn't compile, as I think I stated in an earlier post.

Quote:

---

Without seeing your code or the command line you're using to run your program, only guesses are possible. However, the problem is either in your code or in the command line you are providing to your program.

The obvious possibilities are

1) "--help" is not the third argument you are supplying after the program name, so the comparison is doomed to failure.

2) You're doing the comparison incorrectly. From your description, you could be doing;

Code:

---

  int result = strcmp(argv[3], "--help");
  if (result = 0)
        do_something();
  else
        do_something_else();

---

A single '=' character does an assignment. A comparison requires two of them. if (result = 0) will always test false (as zero is false).

---

No, I wasn't doing that. The problem stemmed from changing the wrong code to use strcmp() and thinking I was changing the right code. Once I realized my error, and corrected the right code, POOF! went my problem. :) Or something like that...

Quote:

---

3) You are using a command line interpreter that filters "--help", and changes what is being passed to your program. For example, conversion to upper case, stripping one of the '-' characters.

---

Well, I sure hope nothing like that will ever occur when someone uses my program...

Quote:

---

4) You have not ensured argv[3] is valid. You also need to check argc. For example, if argc is less than 4, using strcmp(argv[3], anything) always gives undefined behaviour.

---

Oh, I ensured it, alright. I just didn't post all the code that I have.
Obviously I took care of all the obvious things such as that. ;) Its the subtle errors that are harder to find.

Quick question though:

Does the string::c_str() function work with comparison operators such as '!=' and '==', if I use those operators with the other operand being a literal c-style string?

Quote:

---

Originally Posted by Programmer_P

Ok, another problem dealing with argv:

When I get the argv[1] argument and store it in a string, I then get the size of the string by calling the size() function of that string.
Later on in the code, I was noticing it was outputting the wrong message at was supposed to be the last character of the string (i.e. inputFilePathSize - 1). And so I went and outputted the size of the inputFilePath string (which is the string which was given the contents of argv[1]), and it turns out that size is 2 less than what it should be.

It claims the length/size of the string is 32, when in reality, its 34. It also gets the size of argv[2] (an output filename string) wrong. It claims it has 7 characters, when in reality, it has 9.

With both strings, I depending on the size() function of the string type, and store what that function returns inside an int. Is that the problem? I know that string::size() returns a size_t type which is an unsigned type as opposed to "int" which is a signed type. I don't know if that would change the inner value though. I was under the impression it wouldn't, which is why I'm using an int variable instead of a size_t for storing the size.

---

And this problem still exists...
My program will compile, but its not calculating the sizes of two C++ strings correctly, even though I use the string::size() function to get the sizes. It calculates the size of both as 2 less than what the size/length of the strings really are.

No. The string::c_str() function returns a cstring. You then have to use strcmp().

Quote:

---

Originally Posted by jimblumberg

No. The string::c_str() function returns a cstring. You then have to use strcmp().

---

The problem is, that function can only compare two c-style strings. I want to compare a C++ string with a c-style string, without converting one to another first.

How are you storing argv[1] to a string??

Quote:

---

No. The string::c_str() function returns a cstring. You then have to use strcmp().

---

No. You see, when you type a literal C-string into your program, the compiler sets aside some memory for it in the .text segment (if you're using an Intel machine). Good compilers will make the same literal typed in different places in the program point to the same location in the .text segment. (Note that the .text segment is read-only.)

But when you call .c_str() on a std::string, the code has to take a dynamically allocated string and represent it in C-string form. (On most compilers, this is probably already the internal representation, making this operation trivial.) The difference is that this will be a dynamically allocated object on the heap, not a string stored in the .data segment.

When you use == or != on char*'s, you're just comparing the pointer. That is,

Code:

---

string == "data"

---

checks whether the pointer stored in string is exactly the same pointer as the static .text segment pointer to "data". Since your string pointer is actually on the heap, this should never happen.

The reason == works on std::strings is that the string class overloads the operator ==, to redefine what it does. For basic C-strings, you need to compare strings character by character to determine whether they are the same or not, which is what strcmp() does for you.

[edit] I should mention that argv[] is most likely dynamically allocated as well (or perhaps stored on the heap), so comparing its elements with pointers like "--verbose" in the .text segment is unlikely to work as well. [/edit]

Quote:

---

Originally Posted by jimblumberg

How are you storing argv[1] to a string??

---

Good question.
I'm storing it by assigning argv[1] to a string object called "inputFilePath". That's the same string I check later for its size (of which I store in an int variable), and which size is 2 less than what it should be.

Quote:

---

Originally Posted by Programmer_P

Good question.
I'm storing it by assigning argv[1] to a string object called "inputFilePath". That's the same string I check later for its size (of which I store in an int variable), and which size is 2 less than what it should be.

---

Could you please show the code?

Quote:

---

Originally Posted by jimblumberg

Could you please show the code?

---

Code:

---

string inputFilePath = argv[1];

---

Quote:

---

Originally Posted by Programmer_P

Code:

---

string inputFilePath = argv[1];

---

---

Ok and if argv[1] contains "--help" then inputFilePath.size() should equal 6. If it doesn't then

a. What does it report?
b. What does

Code:

---

std::cout << inputFilePath << std::endl;

---

show?

Quote:

---

Originally Posted by jimblumberg

Ok and if argv[1] contains "--help" then inputFilePath.size() should equal 6. If it doesn't then

a. What does it report?
b. What does

Code:

---

std::cout << inputFilePath << std::endl;

---

show?

---

The thing is, by the time that line gets executed, we know argv[1] is NOT "--help", and contains the input filepath, hence the name "inputFilePath" which is correct. That is why the length of the argument argv[1] I passed in was/is 34, but it outputs 32 when I output its size. I will go change the code though to output not only the size of the inputFilePath, but also the content as well. I just assumed before that the content was the same as the passed in filepath.

Hmm...
The content of the input file path is the same as what I passed in except its missing the double quotes I surrounded it with. That explains why the size is 2 less than what it should be.
Another odd thing is, I outputted the character at inputFilePathSize - 1 (which should be the last character of the string), and it reports that it is a '/' character instead of a 'p' character (last character of '.cpp') which is the last character of the inputFilePath string that gets outputted...
Why the inconsistency, I have no idea.

Then it is the correct size because the quotes are removed.

Quotes around parms passed as arguments get stripped for you.

Quote:

---

Originally Posted by Dino

Quotes around parms passed as arguments get stripped for you.

---

That sucks...
I was wanting to keep the quotes. I LIKE QUOTES!!! :p

Thanks. So how do I check then to see if the user entered quotes?

So how do I check then to see if the user entered quotes around the filepath?

Quote:

---

Originally Posted by Programmer_P

Well, that is what I originally guessed was happening if I compare argv[3] with a literal string. However, when I attempted to dereference the pointer at element 3 of argv, it wouldn't compile, as I think I stated in an earlier post.

---

That's because dereferencing the pointer means you are comparing the value of one character with the address in memory of another character. Such comparisons don't make sense, so compilers reject them.

Quote:

---

Originally Posted by Programmer_P

Does the string::c_str() function work with comparison operators such as '!=' and '==', if I use those operators with the other operand being a literal c-style string?

---

No. The result of string::c_str() is a pointer. If you use the comparison operators on it, you are doing a pointer comparison. If you want to compare the data that pointer points at with the data pointed at by another pointer (eg a string literal) then use strcmp().

Quote:

---

Originally Posted by Programmer_P

So how do I check then to see if the user entered quotes around the filepath?

---

Why do you need to know that the user entered quotes? The quotes allow a parameter to have spaces embedded in it. eg "the big c++ program" will be one argument not the 4 it would be without the quotes.

Quote:

---

Originally Posted by grumpy

That's because dereferencing the pointer means you are comparing the value of one character with the address in memory of another character. Such comparisons don't make sense, so compilers reject them.



No. The result of string::c_str() is a pointer. If you use the comparison operators on it, you are doing a pointer comparison. If you want to compare the data that pointer points at with the data pointed at by another pointer (eg a string literal) then use strcmp().

---

Thanks for that, but I'm already using strcmp() and that part of my code is working.

Quote:

---

Originally Posted by jimblumberg

Why do you need to know that the user entered quotes? The quotes allow a parameter to have spaces embedded in it. eg "the big c++ program" will be one argument not the 4 it would be without the quotes.

---

Exactly. I want to accept filenames which might have spaces in them.

Well, since it's a char array, you can use the == operator on the first char of the parm element. That should make you happy!

Code:

---

if (argv[1][0] == '\"') { already a double quote.... }

---

Quote:

---

Originally Posted by Dino

Well, since it's a char array, you can use the == operator on the first char of the parm element. That should make you happy!

Code:

---

if (argv[1][0] == '\"') { already a double quote.... }

---

---

But I thought the quotes are already stripped from the arrays being pointed at by argv's elements?

Quote:

---

Originally Posted by Programmer_P

That sucks...
I was wanting to keep the quotes. I LIKE QUOTES!!! :p

Thanks. So how do I check then to see if the user entered quotes?

---

So, I tell you how. Then you say:

Quote:

---

Originally Posted by Programmer_P

But I thought the quotes are already stripped from the arrays being pointed at by argv's elements?

---

OMG!! Make up your friggin mind for which direction you are going with your conversation.

C Runtime didn't change between these last few posts. Yes, they are removed. I gave you a sample of how to test for quotes, and I just happened to use argv[1] - but it is not impossible to pass quotes, but the outer quotes are removed by default.

You don't need quotes to open a file. If you want quotes, add them back in. But take them out again if you plan on actually opening the file. Holy cow.

What we have here

Yes we do.

Quote:

---

Originally Posted by Dino

So, I tell you how. Then you say:



OMG!! Make up your friggin mind for which direction you are going with your conversation.

---

My mind didn't change direction. I said I wanted to keep the quotes, then I asked how to do that? Then when you responded with an if statement to check if the first character of the argv[1] is a double quote character, I questioned it because in my understanding, the quotes are already stripped from the array somehow. What's wrong with that?

Quote:

---

C Runtime didn't change between these last few posts. Yes, they are removed. I gave you a sample of how to test for quotes, and I just happened to use argv[1] - but it is not impossible to pass quotes, but the outer quotes are removed by default.

---

So you're saying someone would have to pass double double quotes in order for one of them to stay?

Quote:

---

You don't need quotes to open a file. If you want quotes, add them back in. But take them out again if you plan on actually opening the file. Holy cow.

---

It was my understanding that if I pass quotes in the filepath I pass to ifstream::open, then a file with spaces in the filename can open. Otherwise it can't. Is this incorrect?

Quote:

---

Originally Posted by Programmer_P

So you're saying someone would have to pass double double quotes in order for one of them to stay?

---

Try it and you tell me.

Quote:

---

Originally Posted by Programmer_P

It was my understanding that if I pass quotes in the filepath I pass to ifstream::open, then a file with spaces in the filename can open. Otherwise it can't. Is this incorrect?

---

A C-string is passed - blanks or any other characters don't have anything to do with it - it's all about the null terminator ending the file name.

Quote:

---

Originally Posted by Programmer_P

Quick question though:

Does the string::c_str() function work with comparison operators such as '!=' and '==', if I use those operators with the other operand being a literal c-style string?

---

Well yes, but it won't do what you expect it to do. As mentioned earlier, an array of char's is actually a pointer. The c_string() function in std::string returns a const pointer to an array of chars, so if you do something like this:

Code:

---

if(myStdString.c_str() == "--help")

---

...you will NOT be comparing the contents of the std::string with the constant of the C-style string, you will be comparing the MEMORY ADDRESS of the two. The pointer returned by the c_str() function might point to a random address like 0x00241 and the "==" operator will then check if the "-help" string also resides in 0x00241, which it ofcourse does not.

What you WANT to do is this:

Code:

---

#include <cstring>
...
if(std::strcmp(myStdString.c_str(), "--help") )

---

This will compare the CONTENTS of the strings, not the memory address, and i think this is what you really want.

Yeah this you can do by using"operator overloading" for which you need to write a function

Quote:

---

Originally Posted by Neo1

Well yes, but it won't do what you expect it to do. As mentioned earlier, an array of char's is actually a pointer. The c_string() function in std::string returns a const pointer to an array of chars, so if you do something like this:

Code:

---

if(myStdString.c_str() == "--help")

---

...you will NOT be comparing the contents of the std::string with the constant of the C-style string, you will be comparing the MEMORY ADDRESS of the two. The pointer returned by the c_str() function might point to a random address like 0x00241 and the "==" operator will then check if the "-help" string also resides in 0x00241, which it ofcourse does not.

What you WANT to do is this:

Code:

---

#include <cstring>
...
if(std::strcmp(myStdString.c_str(), "--help") )

---

This will compare the CONTENTS of the strings, not the memory address, and i think this is what you really want.

---

I thank you, but...
How many times are people going to answer that question?? :)
We've been through all this already. For the last time, I now know you must always use strcmp() to compare two c-style strings, and if you want to compare a C++ string with a c-style string, then you just pass to strcmp the c_str() function of the string in one of the parameters. I get it now. I really do..
I'm way past that problem now.

Is there anyway I can mark this thread as solved?

Quote:

---

Originally Posted by Neo1

As mentioned earlier, an array of char's is actually a pointer.

---

Actually, an array of chars is an array of chars, not a pointer. However, in most contexts, an array is implicitly converted to a pointer to its first element.

Quote:

---

Originally Posted by Neo1

The c_string() function in std::string returns a const pointer to an array of chars

---

More accurately, the c_str() member function of std::string returns a pointer to a const char, and this const char is the first in a null terminated array of char corresponding to the contents of the std::string.

Quote:

---

Originally Posted by Neo1

What you WANT to do is this:

Code:

---

#include <cstring>
...
if(std::strcmp(myStdString.c_str(), "--help") )

---

This will compare the CONTENTS of the strings, not the memory address, and i think this is what you really want.

---

A catch here is that this compares the contents to check if they are not equal. Unless you have some special reason to use the c_str() member function here, it would really be simpler to do without it, e.g.,

Code:

---

if (myStdString == "--help")

---

Quote:

---

Originally Posted by skumarisation

Yeah this you can do by using"operator overloading" for which you need to write a function

---

Yeah, I know about operator loading, but I was hoping that the STL would already support using "==" or "!=" with two c-style strings. I don't know why the developers of the C++ STL haven't added it.

Quote:

---

Originally Posted by Programmer_P

I don't know why the developers of the C++ STL haven't added it.

---

They cannot, as one cannot overload on the built-in and pointer types without involving a class type. But a simple solution exists: create a std::string from one of the C-style strings.

Quote:

---

Originally Posted by laserlight

A catch here is that this compares the contents to check if they are not equal. Unless you have some special reason to use the c_str() member function here, it would really be simpler to do without it, e.g.,

Code:

---

if (myStdString == "--help")

---

---

Yeah, but the problem is "--help" is a c-style string, and "myStdString" is a std::string.
And the std::string type doesn't have a '==' operator.

std::string DOES have an == operator.
The above code is perfectly legal.

Quote:

---

Originally Posted by laserlight

They cannot, as one cannot overload on the built-in and pointer types without involving a class type.

---

Yeah...so why not involve a class type??

Quote:

---

Originally Posted by Programmer_P

And the std::string type doesn't have a '==' operator.

---

I see. Compile this program and tell us the compile error. If there is no compile error, run the program and tell us the output:

Code:

---

#include <iostream>
#include <string>

int main()
{
    std::string myStdString = "--help";
    if (myStdString == "--help")
    {
        std::cout << "Programmer_P";
    }
    else
    {
        std::cout << "laserlight";
    }
    std::cout << " is wrong." << std::endl;
}

---

Quote:

---

Originally Posted by Programmer_P

Yeah...so why not involve a class type??

---

That is precisely what I am telling you to do: involve a class type by constructing a std::string from one of the null terminated C-style strings.

Quote:

---

Originally Posted by Elysia

std::string DOES have an == operator.
The above code is perfectly legal.

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string - C++ Reference

I don't see any '==' operator...

Quote:

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Originally Posted by laserlight

I see. Compile this program and tell us the compile error. If there is no compile error, run the program and tell us the output:

Code:

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#include <iostream>
#include <string>

int main()
{
    std::string myStdString = "--help";
    if (myStdString == "--help")
    {
        std::cout << "Programmer_P";
    }
    else
    {
        std::cout << "laserlight";
    }
    std::cout << " is wrong." << std::endl;
}

---

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Ok, fine then...I'm wrong. :)
I'll blame it on the writers of the string documentation reference article I just linked to at cplusplus.com.

Quote:

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Originally Posted by laserlight

That is precisely what I am telling you to do: involve a class type by constructing a std::string from one of the null terminated C-style strings.

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I meant, why didn't the C++ STL developers involve a class type so they could overload the '==' operator?

Quote:

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Originally Posted by Programmer_P

I'll blame it on the writers of the string documentation reference article I just linked to at cplusplus.com.

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Unfortunately for you, they did include those operators: comparison operators ;)

Quote:

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Originally Posted by Programmer_P

I meant, why didn't the C++ STL developers involve a class type so they could overload the '==' operator?

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What you want to do is overload operator== for pointer types. If you involve a class type, then you are no longer doing what you set out to do.

Quote:

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Originally Posted by Programmer_P

string - C++ Reference

I don't see any '==' operator...

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It may be hard to find a complete reference, but they exist, and so does operator==.

Quote:

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Originally Posted by the link

template <class charT, class traits, class Alloc>
bool operator==(const basic_string<charT, traits, Alloc>& s1,
const basic_string<charT, traits, Alloc>& s2)

Container String equality. A global function, not a member function.

template <class charT, class traits, class Alloc>
bool operator==(const charT* s1,
const basic_string<charT, traits, Alloc>& s2)

basic_string String equality. A global function, not a member function.

template <class charT, class traits, class Alloc>
bool operator==(const basic_string<charT, traits, Alloc>& s1,
const charT* s2)

basic_string String equality. A global function, not a member function.

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Most references must not cover global functions introduced by the class. :(

Quote:

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Originally Posted by laserlight

Unfortunately for you, they did include those operators: comparison operators ;)

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Ok, but why didn't they put a link to that article on the main C++ string article, which I linked to?

Quote:

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Originally Posted by Programmer_P

Ok, but why didn't they put a link to that article on the main C++ string article, which I linked to?

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They did, but I suppose you can fault them for not making it very prominent, heheh.

Quote:

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Originally Posted by laserlight

They did, but I suppose you can fault them for not making it very prominent, heheh.

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Yeh, its on the sidebar, but I meant why didn't they put it on the main part of the page.
Anyway, ok, I stand corrected...................

Quote:

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Originally Posted by Programmer_P

Ok, but why didn't they put a link to that article on the main C++ string article, which I linked to?

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Well, one persons idea of how documentation should work is not always anothers, that is fer sure. :p

I think the "reference" section of cplusplus.com is intended more as a reference than for truly pedagogical purposes, which it is pretty good for that IMO. Once you have learned something, you will probably still need a reference, but the tutorial or whatever you learned it from may not make a good one. See the difference?

I notice they do have some tutorials, I haven't used them because I kind of prefer books where-ever possible for learning new things. If you live near a city with a public library system, I think you will be pleasantly surprised by the number of beginner C++ books available.

If not, you can probably find a used one on Amazon for ~$10. I've bought a few used books thru amazon affiliates, and tho I always pick the very cheapest one (eg, $0.49 for a $50 title :)) they have all been in excellent condition -- in fact, a couple of them turned out to be brand new.