Hello again awesome team of coders......
I know using (preprocessor?) 'using namespace std;' gives same result that 'std::count/std::cin' but since I noticed both syntax are used in books I wonder what is consider 'best practice' on this regard?
Also noticed that some code editors (like atom, for example) default to 'std::...' syntax even if 'using namespace std' has been specified so I'm curious about what should be the more appropriate?
Thanks.
Never put a "using namespace" directive in a header file, in the global namespace. That's the best practice. I prefer not to use "using namespace" at all, but that's more a matter of personal preference.
thanks.
It's not considered a good practice to be `using namespace` because of how C++ does overload resolution and you may get unintentional results if you're using a function that's defined in more than one namespace.
Instead, it's typically accepted to enumerate your `using`s so you'd type:
To this end, anyone reading your code can now know _exactly_ what functions you're importing from the namespace.Code:using std::vector;
using std::string;
using std::cout;
/* ... */
Edit:
The worst was when I was trying to read some code and they did this:
Good luck looking up where each function comes from!Code:using namespace folly;
using namespace std;
using namespace proxygen;
Accepted by whom?Quote:
Instead, it's typically accepted to enumerate your `using`s so you'd type:
IMO enumerating your using statements in the global space should be avoided as well. Keep all of your using statements as local as possible and prefer properly scoping the namespace with the scope resolution operator::.
Jim
I don't think there is really a best practice about this. The only hard rule was written in this thread here.
Like stated earlier it can be a personal preference, and the rules of name lookup can force your hand. Programs will also look like crap if you convince yourself that one shortcut is better than another shortcut.Quote:
Never put a "using namespace" directive in a header file, in the global namespace. That's the best practice.
I don't really mind using namespace statements, but the only stance I can advocate for is doing what you have to do to get name resolution to work. You'll get into an internet argument if you care about this too much.
Yeah, never do it in a header file in global namespace, it can mess things up, but otherwise... I'd stick to using it as locally as I could, but as long as you know it won't screw you - you're probably fine.
using namespace std; always seemed like an easy cop-out for existing programs which suddenly had to deal with namespace aware compilers.
An easy one-line fix, and your programs still compiled.
But new code should take a much more refined approach to namespaces, especially when you have multiple namespaces in use at the same time.
Sure, having to write
std::cout << "hello world" << std::endl;
is a PITA, but no one is ever going to be in any doubt as to what you meant.
using std::cout; might be a comfortable half-way point if you use a lot of one particular aspect of a particular namespace.
Quote:
using std::cout; might be a comfortable half-way point if you use a lot of one particular aspect of a particular namespace.
Yeah, that was my thinking as well. Writing the entire name of something is incredibly annoying but the `using` stuff can help. Especially when your library is like 7 namespaces deep.
If you have "long" namespaces then you might be better off considering a namespace alias rather than the using statements.
Jim
My biggest gripe is that heavy usage of a library makes namespaces less than desirable. But that's obviously incredibly subjective.
Another thing that can sway a new coder one way or the other is
text books and colleges. Some of Deitel's older C++ books used to teach std::
prefix throughout. Their newer versions all teach using namespace std; as the
"standard", as they say. Not a major thing - but it can prevent some students new
to the language learning about other ways to include namespace objects into their
programs.
Why, are there C++ programmers out there who doubt whatQuote:
Originally Posted by Salem
cout << "hello world" << endl;
means?
I think Salem was talking about from a programmers "too much to type" sort
of way, being having to put the std:: prefix before every namespace object etc. :)
On a side note, so this is pretty much offtopic... I found plenty of people that didn't quite know what std::endl does, so there's that.Quote:
no one is ever going to be in any doubt as to what you meant
It doesn't just add new-line to the stream, it also flushes it, which may degrade performance if looped over... Which is why I use it only where I want to both - add a new-line character and flush immediately. "hello world\n" is shorter to write anyway. ;)
So yes, no doubt which endl is used here, if there are many, but there may be superficial knowledge on what it does anyway. ;)
/offtopic.