C++ Question

sleepyhomme · 07-31-2008, 07:07 AM

I am new to C++. I am very confused is there any difference between the 2 blocks of code below

Code:

template<typename T>
void print(const T& var) {
    std::cout << var << std::endl;
}

and

Code:

template<typename T>
void print(const T &var) {
    std::cout << var << std::endl;
}

My question is the & sign (reference-of operator). Any difference between T& var and T &var?...

Thanks for any help!

Nauntilus · 07-31-2008, 08:10 AM

Yes, it should be &var the & is supposed to go before the variable that it is associated with. also, are you using any uncommon namespaces? because instead of using std::cout you could use just cout if you did this at the beginning of the file.

#include <iostream>
using namespace std;

then you could use just cout and it would save you alot of time typing and far less errors

Nauntilus · 07-31-2008, 08:12 AM

What exactly are you trying to do with that code? because I don't think that that is your only problem, it looks like you are wanting to send two variables into your function, but you need to add a semi-colon (

in between them in the function header.

Nylex · 07-31-2008, 08:19 AM

The code looks fine to me, T is not a variable but a type specifier (I'm not sure what the proper term is).

As far as T& var and T &var are concerned, I think they mean the same thing. People do the same with pointers (e.g. int* my_pointer or int *my_pointer).

sleepyhomme · 07-31-2008, 08:20 AM

I am learning C++ through oopweb.com. The text there are quite good so far. The code i asked is copied from the web below.

http://oopweb.com/CPP/Documents/CPPH...-HOWTO-16.html

I juz dun understand it, that's why i post my question here!

Nauntilus · 07-31-2008, 08:26 AM

There is some more user friendly stuff out there to learn C++ I have tried nearly every website and book that you can buy, lol well not EVERY book or website. But, the best one that I have found is called "Object-Oriented Program Development Using C++" the ISBN is 0-619-15966-9. and this was the easiest for me to learn out of myself. I would definitely check it out if I were you, it is only about $30. and it is far less confusing then that website you were on!

sleepyhomme · 07-31-2008, 08:28 AM

Thanks. Let me check whether it's in Safari!

Nylex · 07-31-2008, 08:28 AM

As far as books go, I found Ivor Horton's books to be quite easy to follow.

Nauntilus · 07-31-2008, 08:43 AM

The book I am referring too is actually a college textbook for their first computer science class, and I learned more reading that book then any other book. SO, if you are looking it up on like amazon or half, you might have to go to the text book area.

matthewg42 · 07-31-2008, 10:01 AM

I thought that this sort of difference was analagous to the difference between:

Code:

char* c;

and

Code:

char *c;

...which makes no difference to the compiled result. For simple statements I think the difference is only really stylistic.

dmail · 07-31-2008, 01:21 PM

That is correct matthewg42, the reasons for using one form or another normally boil down to the idea of cleanliness when declaring pointers. for example

Code:

char *c,d,e;
//compared to:
char* c,d,e;

Yet this argument is mute really for references as they must be seated when declared.
char a = 56;
char &c,d = a;//invalid

sleepyhomme I have had a look at the reference docs which you are using as a learning aid and would have to reiterate the point that they are not a good learning source. I found a number of incorrect statements and facts, in addition his logic for the function 'zap' is just plain stupid.
See the following for a recommended reading.
http://www.parashift.com/c++-faq-lite/
http://www.mindview.net/Books/TICPP/...ngInCPP2e.html

sleepyhomme · 07-31-2008, 11:05 PM

OH~ I have also started to read the C++ FAQ last night.
Thank you so much for your recommendation!!!

ta0kira · 08-03-2008, 06:40 PM

It's all in your style of code. I personally place pointer and reference qualifiers next to the variable name because they're associated with the variable, not the type. As was implied above, you get a pointer and an object doing this:

Code:

int* A, B;

but two pointers doing this:

Code:

int *A, *B;

It makes no difference which because the C++ ISO is too freaking huge as it is without arbitrary whitespace restrictions. You could even do this:

Code:

int*A,*B;

which many developers do. Use a style that makes sense to you, but be prepared to learn new styles if you ever plan to work with other developers.
ta0kira

sleepyhomme · 08-03-2008, 11:21 PM

I get it, man. Thank you