On Friday 28 March 2003 02:39 am, Derek Fountain wrote:

Show us the code! My guess is you are actually using instead of <iostream>. For me, compiling:

#include <iostream>

int main( int argc, char *argv[] ) { std::cout << "derek" << "\n"; return 0; }

with:

g++ -o iostream iostream.cpp

works fine.

No need. The code is almost identical you yours. The Part I didn't know to do whas "std::". And the "endl" seems to be a thing of the past as well. Thanks for the help. This should give you an idea of how long it's been since I worked with C++. STH

On Friday 28 March 2003 04:31 am, Mads Martin Jorgensen wrote:

* Steven T. Hatton [Mar 28. 2003 10:27]:

...

No need. The code is almost identical you yours. The Part I didn't know to do whas "std::". And the "endl" seems to be a thing of the past as well.

std::endl still works fine. You gcc have just become more anal with the namespaces.

-- Mads Martin Joergensen, http://mmj.dk

I'm still confused about documentation. What documentation covers the standard C++ libraries in gcc? STH

On Friday 28 March 2003 05:42 am, Derek Fountain wrote:

...

I'm still confused about documentation. What documentation covers the standard C++ libraries in gcc?

How about:

http://gcc.gnu.org/onlinedocs/libstdc++/documentation.html

?

Of course, whether they help or just confuse you even more is a question only you can answer. For STL stuff I have the SGI docs bookmarked:

http://www.sgi.com/tech/stl/

although gcc uses the HP implementation. It's all the same (bugs excluded). Even then I tend to go and look in the header files for what I'm after, just because it's quicker to grep than do a web search.

They seem extraordinarily incomplete. I'm trying to figure out things that should be simple, such as how to work with the string class. How do I create a string type variable within a class, and assign a value to it? STH

On Friday 28 March 2003 07:34 am, Derek Fountain wrote:

...

They seem extraordinarily incomplete.

That's often the nature of free software documentation, I'm afraid. :o( The SGI stuff is OK, though.

$ locate string.h | grep gcc /opt/gcc-3.2/include/c++/3.2/bits/basic_string.h $ less /opt/gcc-3.2/include/c++/3.2/bits/basic_string.h // Components for manipulating sequences of characters -*- C++ -*- ... // ISO C++ 14882: 21 Strings library ... // Documentation? What's that? // Nathan Myers . // ... So, is this the file that answers to <string>?

...

I'm trying to figure out things that should be simple, such as how to work with the string class.

Consider using a toolkit of some sort. The C++ standard library is horrible to work with and should be avoided where possible[*]. The best toolkit on the market at the moment is Qt[*], which isn't just a GUI toolkit, it gives data structures, strings, XML handling and all sorts of other stuff. Extremely well put together, excellent documentation and hundreds of examples. If you're doing GPL software, consider using Qt.

[* My opinion, others will differ.]

Oh, certainly. QT's fantastic, and wonderfully documented.

...

How do I create a string type variable within a class, and assign a value to it?

Does this help show the way?:

#include <string> #include <iostream>

int main( int argc, char *argv[] ) { std::string s;

s = "derek";

std::cout << s << "\n"; return 0; }

The following accomplishes the basic goal, but leaves several questions unanswered: #include <iostream> // cout, cin #include <string> using namespace std; // Thanks Tom Bradley. class HelloClass { public: void sayHello(); void setMessage(char * message="Hello C++ World"); private: string str; }; void HelloClass::setMessage(char * message){ str = message; } void HelloClass::sayHello() { cout << str << endl; } main() { HelloClass h; h.setMessage(); h.sayHello(); return 0; } How would I set HelloClass::str to something within the class definion, or constructor? IOW, how do I initialize member variables of user defined types to default values? STH

On Sunday 30 March 2003 09:54 am, Derek Fountain wrote:

...

How would I set HelloClass::str to something within the class definion, or constructor? IOW, how do I initialize member variables of user defined types to default values?

Just write your constructor like this:

HelloClass::HelloClass() { str = "Default string"; }

Or do I misunderstand the question?

OK, now that I have the name space stuff straightened out, that works for me. I was trying things with /new/ and mixing in the namespace resolution syntax, which wasn't working. At this point, I don't even want to think about why. I also got a compile error when I left out the explicit declaration of the constructor, but that was immediately obvious. The next thing I need to figure out is the difference between class HelloClass { ... private: string str; } and class HelloClass { ... private: string * str; } I know one is a pointer, and the other is simply a class member of type /string/. I just need to figure out how the two differ in behavior. I've discovered places where I was able to declare pointers in classes, but not members of the type referred to by the pointer. I'm pretty sure it has to do with how the constructors of the member types behave, I'm just not sure what exactly is causing the problems. If I can't figure it out, I'll see if I can formulate a good example to demonstrate the problem. This is, IMO, the kind of Hello World that should be a standard example for working with the string class, perhaps with a good example of a pointer to a string being used as well: #include <iostream> // cout, cin #include <string> using namespace std; class HelloClass { public: HelloClass::HelloClass(); void sayHello(); void setMessage(char * message="Hello C++ World. Default setMessage."); private: string str; }; void HelloClass::setMessage(char * message){ str = message; } void HelloClass::sayHello() { cout << str << endl; } HelloClass::HelloClass(){ str = "Hello C++ World. Declared in constructor."; } main() { HelloClass h; h.sayHello(); h.setMessage(); h.sayHello(); h.setMessage("User defined \"Hello World\" message."); h.sayHello(); return 0; }

-- "...our desktop is falling behind stability-wise and feature wise to KDE ...when I went to Mexico in December to the facility where we launched gnome, they had all switched to KDE3." - Miguel de Icaza, March 2003

On Sunday 30 March 2003 04:57 pm, Jerry Feldman wrote: ...

Then to print the string, you may want to create a friend function so that you can do something like:

HelloClass hw("Hello, World!");

cout << hw << endl; This should be in one of your books.

This looks a lot like the MyClass.toString() of Java. I'm not sure I have the best books for learning C++. The Ellis and Stroustrup book seems to be about 50% apology for doing things Stroustrup would rather not have, but for the desire to cooperate with existing C program(mer)s. It's interesting, but certainly doesn't present the language as deftly as K&R does C. K&R is one very well written book. I have Horstmann's 1991 edition. It's probably dated. Pohl's book is likewise a decade old. I'm sure they are all worth reading, but they probably don't provide the best treatment of recent advances, and imporved libraries, etc. They will have to do for now, however.

Let the constructor assign the the string. That does not eliminate the desire for setting a message, but you can also use some overloading such that: hw = "New Value";

For the HelloClass, using a pointer is probably not altogether useful. But, you also need to be aware of some subtle performance issues. But, at this stage, try to concentrate on setting up constructors with optional arguments and default values. Without complexity, look at setting up things like copy constructors: HelloClass::HelloClass(HelloClass &s) { str = s.str; }

Assignment operator, and possibly concatenation. You wil be reinventing the wheel a bit, but you will also be learning. Don't worry too much about efficiency. Once you are experienced in the language, then you can be more efficient.

In any kind of computer programming, the most important issue is to accomplish the task at hand. But, I always try to make my code readable and maintainable. One reason is that I have had to maintain some horrible code (eg. the sources for YACC and LEX). The other reason is that I want those who come behind me not to curse me. In this industry there are always cases where when looking for a job, someone who knows you may be on the hiring side. But even for your own personal code, you might put it down and not look at it for a while.

I place readability very high on my list of priorities. Good structure is also very important. I've wasted a good deal of time debugging problems that arose because I tried to cut corners. Basically I believe in always writing code 'correctly', hense the question about undepricated Hello World. I could have simply turned off the deprication message and continued to march. I also belive in finding a reasonably good solution to a generic problem, and applying it consistently rather than inventing different 'creative solutions' to the same problem. C++ seems to be rife with opportunities to hang yourself with the available rope. One concern I have is to learn 'safe' coding in C++. I know there are all kinds of pitfalls that Java simply doesn't allow you to get near. Most of these have to do with pointers and memory management. I took a look at http://lxr.mozilla.org/seamonkey/source/security/nss/cmd/certcgi/certcgi.c and found myself amazed, horrified, amused and baffled. STH

Steven T. Hatton wrote:

This looks a lot like the MyClass.toString() of Java. I'm not sure I have the best books for learning C++. The Ellis and Stroustrup book seems to be about 50% apology for doing things Stroustrup would rather not have, but for the desire to cooperate with existing C program(mer)s. It's interesting, but certainly doesn't present the language as deftly as K&R does C. K&R is one very well written book. I have Horstmann's 1991 edition. It's probably dated. Pohl's book is likewise a decade old. I'm sure they are all worth reading, but they probably don't provide the best treatment of recent advances, and imporved libraries, etc. They will have to do for now, however.

You might try something like Deitel & Deitel given that you're newer to C++ but already know java. Stroustrup's C++ book is good but a little harder. Ellis and Stroustrup is older, very definitive and very difficult to read. I use it only when I need to know how something really obscure works. -- JDL

I know one is a pointer, and the other is simply a class member of type /string/. I just need to figure out how the two differ in behavior. I've discovered places where I was able to declare pointers in classes, but not members of the type referred to by the pointer. I'm pretty sure it has to do with how the constructors of the member types behave, I'm just not sure what exactly is causing the problems. If I can't figure it out, I'll see if I can formulate a good example to demonstrate the problem.

As you say one is a pointer, and one is a class. The pointer holds an address in memory. It takes 4 bytes (probably, depending on architecture, etc.) and just holds a single number. End of story. The class member is a complete class instance held in memory, taking as much space as the class takes. Potentially that could be many bytes - or even many megabytes. They both work in the same way, only with the pointer you have to dereference it before you can utilise the class instance it points to. That is, you have to add the syntax which says "work with the object this pointer points to, not the pointer itself". Dereferencing is normally done with the -> operator for individual class members, or the * operator for the entire object. When creating a pointer, the compiler doesn't need to know the entire definition of the object. So you can say: class MyClass; class SomeOtherClass { ... private: MyClass* pointer; 'pointer' will just be 4 bytes and the compiler will note the class it's pointing to, but at this stage it doesn't need to know the details of MyClass - just being told there is a class called that is enough. When, elsewhere in the code, 'pointer' is dereferenced, the code at that point will need to know the full definition of MyClass. This might explain your "I can create a pointer but not an object" puzzle. If you want the object, you need to ensure the compiler can see the full definition of the class you're instantiating. You probably need to #include the appropriate header file. -- "...our desktop is falling behind stability-wise and feature wise to KDE ...when I went to Mexico in December to the facility where we launched gnome, they had all switched to KDE3." - Miguel de Icaza, March 2003

On Friday 28 March 2003 11:11 am, O'Smith wrote:

Steven, This is my most basic "hello world" in c++. How does yours differ?

#include

int main() { cout << "Hello World!\n"; return 0; }

Patrick

Perhaps you have deprication messages turned off, or you don't care about them. I understand this will compile. I just want to know what Stallman et al think I /should/ be doing. This is what I get with your code: g++ hello.cpp In file included from /usr/include/g++/backward/iostream.h:31, from hello.cpp:1: /usr/include/g++/backward/backward_warning.h:32:2: warning: #warning This file includes at least one deprecated or antiquated header. Please consider using one of the 32 headers found in section 17.4.1.2 of the C++ standard. Examples include substituting the <X> header for the header for C++ includes, or <sstream> instead of the deprecated header . To disable this warning use -Wno-deprecated. STH

On Sun, 30 Mar 2003 22:34:35 +0800 Derek Fountain wrote:

If you're working with a language as complex as C++, and you really want the details, you need a copy of the standard. It costs money, and isn't free to distribute, but the GCC coders bought a copy and worked to it. If you want to know what Stallman et al were thinking, read the standard. Then you'll know. For most of us, a copy of the Stroustrup book is adequate. I fully concur with Derek. If you are programming in any language, C, C++, Java, COBOL, or even ADA, you should have at least one book to use as a reference as well as some online references to keep track of recent changes as well as compiler differences. I have among my references, the original K&R, K&R 2nd edition, Stroustrup and several more books. If you are a newcomer to C++ or computer programming in general, there are several good (and bad) tutorial books.

-- -- Gerald Feldman Boston Computer Solutions and Consulting ICQ#156300 PGP key id:C5061EA9 PGP Key fingerprint:053C 73EC 3AC1 5C44 3E14 9245 FB00 3ED5 C506 1EA9

On Sun, 30 Mar 2003 11:06:15 -0500 "Steven T. Hatton" wrote:

I have Ellis and Stroustrup's _The Annotated C++ Reference Manual_, as well as _Object-Oriented Programming Using C++_ by Ira Pohl, _Mastering C++_ by Cay Horstmann, and a few others. I guess I'm just used to Java's SDK, and JBuilder. This was my first Java 3D program: JBuilder is an excellent tool, but it is not Java programming per se. You've got some good references. -- -- Gerald Feldman Boston Computer Solutions and Consulting ICQ#156300 PGP key id:C5061EA9 PGP Key fingerprint:053C 73EC 3AC1 5C44 3E14 9245 FB00 3ED5 C506 1EA9