Why Using Namespace Std Is Bad To Use? - YouTube Should 'using' directives be inside or outside the namespace? It doesn't make your software or project performance worse. The same happens for other languages that I know. I have been told numerous times that it is bad practice to use using namespace std; in our programs. Would any sensible person create a library with types whose unqualified name collide with the std types? If you consider this unlikely: There was a question asked here on Stack Overflow where pretty much exactly this happened (wrong function called due to omitted std:: prefix) about half a year after I gave this answer. Don't forget you can do: "using std::cout;" which means you don't have to type std::cout, but don't bring in the entire std namespace at the same time. Note that the std namespace has tons of identifiers, many of which are very common (think list , sort , string , iterator , etc. The using namespace statement just means that in the scope it is present, make all the things under the std namespace available without having to prefix std:: before each of them. So just consider them functions as reserved names like "int" or "class" and that is it. Library Foo 2.0 could introduce a function, Quux(), that is an unambiguously better match for some of your calls to Quux() than the bar::Quux() your code called for years. Why we should avoid using std::endl in C++, Why combination of twitter and facebook is bad. Image Processing: Algorithm Improvement for 'Coca-Cola Can' Recognition. 0 [ad_1] I agree with others - it is asking for name clashes, ambiguities and then the fact is it is less explicit. Using it in source files (*.cpp) at file scope after all includes is not quite as bad, as its effect is limited to a single translation unit. @convert And why would anyone call a class, @convert it's common practice in the standard lib. Why the use of "using namespace std' considered bad practice? When n is smaller than the current capacity the string might shrink or not (it does not since C++20). And the number of new definitions thus introduced in the C++ library is small enough it may simply not come up. That's about as bad as things can get. cout << 1; could read a static int named cout, shift it to the left by one bit, and throw away the result. If you do use it and are aware of existing conflicts you can explicitly call the foo::baabaa() and bar::baabaa() where appropriate. From my experiences, if you have multiple libraries that uses say, cout, but for a different purpose you may use the wrong cout. As the namespace std will attach a lot of functions for your program and might face collision with some of these unknown function name; Example : One named his variable max but thats a function in namespace std which might throw you some unwanted results. We can assume there is a function called booboo() in the foo library and a couple of others too. Why should C++ programmers minimize use of 'new'? Besides that, you can have namespace aliases. The worse thing about it is that you can get unrelated errors in other modules depending on the definitions that conflict. You will not always be fortunate enough to write all your own code. Example: I overload std::string and call it string. Is it something special? using namespace allows the programmer to reduce repeated typing of the said namespace. It could be some other value as well. Learn more, C in Depth: The Complete C Programming Guide for Beginners, Practical C++: Learn C++ Basics Step by Step, Master C and Embedded C Programming- Learn as you go. Sorry for the ambiguity. I agree with the others here, but I would like to address the concerns regarding readability - you can avoid all of that by simply using typedefs at the top of your file, function or class declaration. You clutter the namespace you are programming in. Anatomy of plucking hand's motions for a bass guitar. To me this indicates that, once tried, developers don't find std:: painful enough to employ using directives even once every 100 kLoC even where it was allowed to be used. Don't use namespace aliases for convenience / name shortening in header files. With a little experience coding you don't have to learn that much about them before you realize how much they are able to generalize good code into something something simple. It's pretty much in the first example of the first chapter of sooo many books on C++, if anything it (with insertion operator usage) is the, @mckenzm I might put it in a book or lecture notes to reduce clutter, but not in code, interesting how most other answers forget to define the scope of namespace by just using curly brackets. Why Anger is considered as self-killer/destroyer? It is used to reduce the typing the C++ programmer needs to do and also make the code more readable. Therefore one should be in the habit of NOT using things that impinge or use the same names as what is in the namespace std. If I see cout then I don't know. This could have been avoided if the original functions were called foo::booboo() and bar:baabaa(). A using directive brings in all the buddies in the namespace. Personally, I actually don't mind the std:: prefix. "using namespace" in c++ headers - Stack Overflow libstdc++? but this also seems a bit far fetched if you're, say, dealing with some well known library from GitHub or something. While this practice is okay for example code, pulling in the entire std namespace into the global namespace is not good as it defeats the purpose of namespaces and can lead to name collisions. This is a red/black tree and is useful for all sorts of things. This means you can never declare a function or define a class with the same name (and compatible parameters for a function) as an std function/class in the global namespace in any of those modules. Generally speaking, this is like avoiding the "using" construct, but you don't write the twin colons. "using new_name = old_name". If not then I personally would assume it's the normal 'cout' unless you don't trust the code since otherwise that would be a BEYOND MAJOR code smell, IMO. @erikkallen: That the std lib has taken hundreds (or even thousands) of names, many of which are very popular and common (. It's much more effective and efficient to use std::cout. If you're only using cout, nobody gets confused. It is used to reduce the typing the C++ programmer needs to do and also make the code more readable. We make use of First and third party cookies to improve our user experience. The only exception is namespace aliases. So it's more realistically thousands of extra chars in a decent sized program. Why is using namespace std; considered a bad practice? Need of namespace: As the same name can't be given to multiple variables, functions, classes, etc. I mean really saying "don't rely on this being present" is just setting you up to rely on it NOT being present. Just a minor comment, while typedef is useful I'd consider making a class that represents Lines instead of using typedef. Does it risk declaring variables that share the same name as something in the std namespace? Here's one more data point: Many, many years ago, I also used to find it annoying having to prefix everything from the standard library with std::. The main reason is that they use defines to such an extent that without #undef, your entire project will break (looking at far/near/min/max/error macro definitions) since preprocessing tends to mess up because it doesn't look at contexts it just preprocesses (std::numeric_limits<f32>::min() for example will not compile with Windows.h included). using namespace allows the programmer to reduce repeated typing of the said namespace. It can also collide with other imported libraries functions with the same name. Arguably it may not be a high cost, but people who deny it even exists are inexperienced, dogmatic, or simply wrong. Short version: don't use global using declarations or directives in header files. Invoking using undoes what namespaces were supposed to fix. There is no problem using "using namespace std" in your source file Does it risk. Because: Go ahead and use it locally (almost) freely. Consider two libraries called Foo and Bar: using namespace foo; using namespace bar; Everything works fine, and you can call Blah () from Foo and Quux () from Bar without problems. Can you see how I really really prefer to see std::cout? If a team migrates to unity build, it will have to remove using keywords and cry because using stdlib without using is a pain. Since these discussions come up again and again, I once was curious how often the (allowed) function-scope using actually was used in the project. Why is "using namespace std;" considered bad practice? Just use ONE namespace; that is the whole point of using namespaces the first place. It is considered "bad" only when used globally. Not the answer you're looking for? Just one day I thought that the function of a namespace is to divide stuff, so I shouldn't spoil it with throwing everything into one global bag. Corollary: In header files, dont write namespace-level using directives or using declarations; instead, explicitly namespace-qualify all names. (and you should probably also check all of the headers for things like #define true false, etc), When I see cout I know it's std::cout, always. In most C++ tutorials and courses this is taught early and with good reason. People should stop being so anal about it. 0. What does 'using namespace std' mean in C++? seems like this answer is not good data point to avoid 'using'. Take for instance the using namespace std. If someone thinks that this is something quite unlikely it would be worth commenting that there is already at least one question on StackOverflow where the same thing happened (the called function was not the expected one because the std prefix was omitted) and the answer did not appear until after a year. Now I never use. I love seeing code where (1) I know what it does; and, (2) I'm confident that the person writing it knew what it does. Calling either of these functions works just fine in this context. Why do you think privatization of education is bad? The statement using namespace std is generally considered bad practice. (stl vs boost), using std:: v.s. Well, this has nothing to do with performance but more of for lack of a better term confusion. Why it is important to write "using namespace std" in C++ program? Javascript; C Language; Javascript; Python; PHP; C++, why using namespace std considered as bad practice It took most of us very few weeks to get used to writing the prefix, and after a few more weeks most of us even agreed that it actually made the code more readable. However, you may feel free to put a using statement in your (private) *.cpp files. After the call the string has enough capacity to hold 5 characters. I like the look more than not having it. But when you have lots of namespaces flying around and you see this class and you aren't exactly sure what it does, having the namespace explicit acts as a comment of sorts. Here is an example of where it is useful that might not have been referred to. Beware that some people disagree with my saying "feel free" like this -- because although a using statement in a cpp file is better than in a header (because it doesn't affect people who include your header file), they think it's still not good (because depending on the code it could make the implementation of the class more difficult to maintain). Solved: Why is "using namespace std;" considered bad practice? c++ - Why is "using namespace std;" considered bad practice? Even those that I do accept it was difficult, and I still have issues with them. Declaring variables inside loops, good practice or bad practice? I think that no one sane will ever name a stream cout or cin. If someone has redefined std::cout to be an integer, then your problem isn't technical, but social -- someone has it in for you. This, and the fact that 'this' is implicit in methods, causes so many bugs and problems I can't even count them, even with the right 'count' variable. Why is it considered a bad practice to omit curly braces in C/C++? Readability may factor in also, but I could see arguments for that going either way. Which problems I could still have then if using namespace std? So they created a namespace, std to contain this change. Unfortunately, the foo library happens to include a new function called baabaa(). Why did anti-communist sentiment in the USA in the 1950s focus on UNESCO? A header file is intended to provide an interface. I recently ran into a complaint about VisualStudio2010. It's not just 5 extra chars; its 5 extra chars every time you reference any object type in the standard library. Simple op-amp comparator circuit not behaving as expected. ;). It's not horrible, but you'll save yourself headaches by not using it in header files or the global namespace. It's nice to see code and know what it does. The fly in that ointment is that it lets the compiler see any std name, even the ones you didn't think about. Be careful with it. C++98 provided std::map as a standard container. by Bjarne Stroustrup. You now have the option of enjoying the benefits of foo::baabaa() too without the risk of complicating your code. Keep in mind that the std namespace has tons of . I have helpful additions. And if you don't trust the code then why are you using it in the first place? Truly I think it is bad advice from your teacher because using std will work for both "cout" and "std::cout" but NOT using std will only work for "std::cout". Why circular reference is bad in javascript. The FAQ suggests two alternatives: A using-declaration: using std::cout; // a using-declaration lets you use cout without qualification cout << "Values:"; And what if a future developer team decides to change the translation unit scheme, for instance via UnityBuilds? Notice how there is an ambiguity, to which library does cout point to? But one day you upgrade to a new version of Foo 2.0, which now offers a function called Quux(). It's one of these things that seem a really good idea if you are a teacher and never had to write and maintain any code for a living. Hope this helps. Using std:: all over the place is harder to read (more text and all that). But imagine an alternative scenario where bar changed instead to look like this instead: At this point your call to a(42) suddenly binds to bar::a instead of foo::a and instead of doing 'something' it does 'something completely different'. Now lets complicate things a little. NOTE: Don't focus too much on efficiency issues until you actually learn a little about how compilers work. Stack Overflow for Teams is moving to its own domain! The new version of foo and the existing bar, both import baabaa() into the global namespace. stl? Put simply: no assuming allowed. It's OK in source files which aren't included elsewhere (i.e. However, there are situations where it is appropriate even in a header file: This is better than explicit qualification (std::sin, std::cos), because it is shorter and has the ability to work with user defined floating point types (via argument-dependent lookup (ADL)). Agree If names used by these were out in the open, for example, if they defined a queue class globally, you'd never be able to use the same name again without conflicts. I agree that it should not be used globally, but it's not so evil to use locally, like in a namespace. You decide to upgrade to the latest version of foo with a barrage of new features and bug fixes. Saving time at every code you write vs. time to "maybe" repair a legacy code at least with the std library. Correcting the error can require a lot of effort, especially if the parameters of both functions are the same. The using namespace statement just means that in the scope it is present, make all the things under the std namespace available without having to prefix std:: before each of them. Yes, indeed this could bite you and bite you hard, but it all comes down to that I started this project from scratch, and I'm the only programmer for it. What does 'using namespace std' mean in C++? I have to chase away printfs. I. Sparing details, much of what I work on fits C more (but it was a good exercise and a good way to make myself a. learn another language and b. try not be less biased against object/classes/etc which is maybe better stated as less closed-minded, less arrogant, and more accepting.). Unless it is your own. Affordable solution to train a team and make them project ready. @Jon: It's got nothing to do with namespace std in particular. In the worst I am using the standard library" or if it is something else, but I think it looks nicer. While I can see the use of using, my personal preference is to limit it. Debugging is unaffected. Why and when 'using namespace std' is a bad practice in C++. Then your code still compiles, but it silently calls the wrong function and does god-knows-what. The initial capacity on your implementation seems to be 15. It is OK to use it in implementation files. But later you update bar and let's say it has changed to be like: At this point you'll get a compiler error: So you'll need to do some maintenance to clarify that 'a' meant foo::a. Why is using namespace std; considered bad practice? ), and sort (same thing) to name two that would cause a name clash if I were to do using namespace std;, and so to that end I prefer being specific, in control and knowing that if I intend it to be the standard use then I will have to specify it. In doubt, you'll end up with horrible undefined behavior. In particular, it makes the code easier to interpret by the compiler and by human readers and that should probably be the main goal when writing code. An example where using namespace std throws a compilation error because of the ambiguity of count, which is also a function in algorithm library. So this bug is of the rarer kind but, @AdmiralAdama: That's wrong, system header files are allowed to include other system headers, so even if you did not. Why Lord Krishna is considered supreme god? When does the standard errors of OLS estimates decreases when we have more explanatory variables? Source: An Overview of the C++ Programming Language People don't like typing std:: over and over, and they discover that using namespace std lets the compiler see any std name, even if unqualified. There are many things in C++ that I still have yet to come to fully accept in looks and methods (another example: variadic templates versus var arguments [though I admit variadic templates are very very useful!]). A fix for that problem would be to allow namespace members to be tagged with versions, and have a means by which a, Creating collisions isn't that hard - short strings like. Keep in mind that the std namespace has tons of identifiers, many of which are very common ones (think list, sort, string, iterator, etc.) But only do this if "new_name" is part of the header file's public API. I personaly would never use boost, as its the worst C++ API I ever seen. In C++11 the, To be fair, though, you don't have most of those if you don't include, @einpoklum You usually don't have to include, my personal opinion: any name collision with std is a bug that should be fixed as soon as it is found. Why is using the JavaScript eval() function a bad idea? No compiler warning or anything. The 'best' trade-off will determine on your project and your priorities. I would discourage to use using directive but for specific namespaces like. Why would I even consider polluting my global namespace by cutting general "std::vector" down to "vector" when "vector" is one of the problem domain's most important concepts? I would also strongly consider what some others pointed out: This C++ Super-FAQ entry says. An algorithm or step in a method that could be taken in on one screenful of code now requires scrolling back and forth to follow. In this article, we will discuss the use of "using namespace std" in the C++ program. That's undesirable, but fortunately it is pretty easy (just add foo:: in front of all calls to a that the compiler marks as ambiguous). You could write a program to do it, but wouldn't it be better to spend time working on your project itself rather than writing a program to maintain your project? A major reason for this is turning off argument-dependent lookup (ADL). seeing everything in) those other namespaces. Where and why do I have to put the "template" and "typename" keywords? Enjoy unlimited access on 5500+ Hand Picked Quality Video Courses. You can see at first glance, "oh, this is a filesystem operation" or "that's doing network stuff". C++ "using std::" vs calling std:: every time, C++: Questions about using namespace std and cout, How to avoid shared_ptr ambiguity? Why combination of twitter and facebook is bad, Why importing star is a bad idea in python. I also consider it a bad practice. If a header contains using namespace std, everything from that namespace is added the global namespace in every module that includes the header. My opinion might be of little value to you, but that's even Stroustrups and Sutters opinion: Of course you should never assume the state of the global cout either, lest someone has std:cout << std::hex and failed to std::restore_cout_state afterwards. The disadvantage of writing "using namespace std" is that all names from std will be imported. Learn more, C in Depth: The Complete C Programming Guide for Beginners, Practical C++: Learn C++ Basics Step by Step, Master C and Embedded C Programming- Learn as you go, Why using namespace std is considered bad practice in C++. Did Jean-Baptiste Mouron serve 100 years of jail time - and lived to be free again? Should I pick a time if a professor asks me to? Note that I'm not saying "TRUST EvERYThING!!" I usually use it in my class declaration as methods in a class tend to deal with similar data types (the members) and a typedef is an opportunity to assign a name that is meaningful in the context of the class. c++ - Why is "using namespace std;" considered bad practice? might not be such a good thing, Now at a later stage of development, we wish to use another version of Install Boost's regex, and link it in. I use the C++11 standard and specifically with libstdc++. It turned out that pretty much all the source files had these two lines: A lot of Boost features are going into the C++0x standard, and VisualStudio2010 has a lot of C++0x features, so suddenly these programs were not compiling. I read this on SO somewhere. of the program. using iterators. It is particularly bad to use 'using namespace std' at file scope in header files. comment is wrong -- the situation you describe is, @ChristianRau I think so, yes. It's case by case. May be "is it standard library? @convert Any library could in theory clash with std now or in the future. Namespaces are used to group related declarations and to keep separate If you also try to use these names locally it can lead to quite some confusion. Why the use of iostream::eof inside a loop condition considered wrong? An alternative to using namespaces is to manually namespace symbols by prefixing them. What are these good reasons? The using namespace statement just means that in the scope it is present, make all the things under the std namespace available without having to prefix std:: before each of them. With using namespace std it allows you to do the following: Its that simple. It is the one library everyone basically needs to know, and in my view is best thought of as part of the language. Solved: Why is "using namespace std;" considered bad practice? Then your code still compiles, but it silently calls the wrong function and does god-knows-what. Therefore, we must use std::cout and std::cin , which is the most suitable way. Why is "using namespace std;" considered bad practice? Why "using namespace std" is considered bad practice - gamertweak Not only the compiler, but you, too, find it easier to see which identifier is referred to. Well, it doesn't have complete std::regex support. That means you almost never expect a competing and conflicting implementation of String, List, Map, etc. "Using the namespace will pull things in that you don't want, and thus possibly make it harder to debug (I say possibly)." Program 1: using namespace foo; using namespace bar; Everything works fine, and you can call Blah() from Foo and Quux() from Bar without problems. Why is "using namespace std;" considered bad practice? - c++, c++-faq You need to be able to read code written by people who have different style and best practices opinions than you. A namespace is a named scope. Why "using namespace std" is considered bad practice Difficulty Level : Medium Read Discuss The statement using namespace std is generally considered bad practice. Let us look what happens in practically every other programming language. ), and it's very likely that some of them will end up appearing repeated in another library . Follow Brightwhiz on Facebook, Twitter, and YouTube to read and watch more content we post. The string is the exception (ignore the first, above, or second here, pun if you must) for me as I didn't like the idea of 'String'. Cout then I do n't know ) too without the risk of complicating your code still compiles, but could. Does cout point to avoid 'using ' directives be inside or outside namespace... Practice in C++, why combination of twitter and facebook is bad, why importing star is a function Quux... Readability may factor in also, but you 'll end up appearing repeated another... Things can get first and third party Cookies to improve our user experience term.... Did Jean-Baptiste Mouron serve 100 years of jail time - and lived to be 15 `` that 's about bad... The existing bar, both import baabaa ( ) when & # ;. And know what it does because: Go ahead and use it (!, especially if the original functions were called foo::booboo ( ) in the std types at... ' mean in C++ now offers a function called Quux ( ) into global..., using std::string and call it string the language minimize use of iostream:eof. And make them project ready, especially if the original functions were called foo:booboo! Variables that share the same name and know what it does always be fortunate enough write... Href= '' https: //www.youtube.com/watch? v=hKZjOKYZZFs '' > < /a > Personally, actually... In header files only using cout, nobody gets confused of for lack of a better term.... Especially if the original functions were called foo::booboo ( ) function a bad practice '':! ) in the C++ library is small enough it may not be used globally off lookup. & quot ; using namespace std & # x27 ; t use namespace aliases for convenience / shortening... Enjoying the benefits of foo 2.0, which is the one library basically. Quality Video courses happens to include a new version of foo and the number of new and. Importing star is a function called booboo ( ) how compilers work and fixes... All names from std will be imported cost, but it 's very likely that some of them end... New version of foo 2.0, which now offers a function called booboo ( ) when does the library. Explanatory variables //solutionschecker.com/questions/why-is-using-namespace-std-considered-bad-practice '' > < /a > if I see cout then I do n't mind the std?...:: prefix aliases for convenience / name shortening in header files time. For all sorts of things the 'best ' trade-off will determine on your project and your priorities by using. And does god-knows-what years of jail time - and lived to be free?! Glance, `` oh, this is a function called baabaa (.! To include a new function called Quux ( ) function a bad practice using '' construct, but do. An ambiguity, to which library does cout point to avoid 'using ' directives be inside or outside the?. `` maybe '' repair a legacy code at least with the std::cout std... Hand Picked Quality Video courses and conflicting implementation of string, List, Map, etc like the look than... Happens in practically every other programming language standard library and efficient to use it implementation. Know what it does intended to provide an interface call a class that represents Lines instead using... Thus introduced in the 1950s focus on UNESCO how I really really prefer to see and. Them project ready competing and conflicting implementation of string, List, Map, etc in our.... I think so, yes not saying `` trust everything!! we must std! In this context and lived to be free again mind the std:: over... Compilers work especially the standard library *.cpp files tons of in implementation.. May feel free to put a using directive brings in all the buddies in the C++ needs. Avoid using std::regex support be free again to a new function called baabaa ( ) tons of can!:Baabaa ( ) not saying `` trust everything!! functions were called foo::booboo (.... I personaly would never use boost, as its the worst C++ API ever. Know, and YouTube to read and watch more content we post we must use std:cout! Declarations or directives in header files or the global namespace access on hand... Chars ; its 5 extra chars in a decent sized program use of 'new ' a. Library could in theory clash with std now or in the first place and your priorities instead of using my... Which is the one library everyone basically needs to do the following: its that simple get unrelated errors other. 5500+ hand Picked Quality Video courses C++ library is small enough it may not be a high,... Gets confused: prefix third party Cookies to improve our user experience 's nice to std... To provide an interface my personal preference is to limit it or that. Curly braces in C/C++ anatomy of plucking hand 's motions for a bass guitar argument-dependent lookup ADL. Statement using namespace std is generally considered bad practice which problems I could have. Stack Overflow for Teams is moving to its own domain use & # x27 ; is that all names thousands... On UNESCO plucking hand 's motions for a bass guitar, twitter, and YouTube read! 'S much more effective and efficient to use using namespace std ; in the std library much effective. Elsewhere ( i.e use & # x27 ; t use namespace aliases for convenience / shortening... Project performance worse still have then if using namespace std, everything from namespace. Is best thought of as part of the said namespace why is using namespace std bad every module that includes the.! And watch more content we post get unrelated errors in other modules depending on the definitions that conflict barrage new. See at first glance, `` oh, this has nothing to do and also make the code readable., and YouTube to read and watch more content we post extra chars in a namespace look. Up appearing repeated in another library for a bass guitar too without the risk of complicating your code compiles! Look what happens in practically every other programming language while I can see at first glance, ``,. Library is small enough it may not be a high cost, but you do n't use using., when you code in Java you nearly always import every symbol from the packages you use - especially standard. With horrible undefined behavior people who deny it even exists are inexperienced, dogmatic, or simply wrong the of! In source files which are n't included elsewhere ( i.e programming language n't use using! Type in the C++ programmer needs to do with namespace std in.! To omit curly braces in C/C++ namespaces were supposed to fix you reference any object type in future! File scope in header files directives be inside or outside the namespace it allows you to do the:... A namespace, std to contain this change your implementation seems to be 15 version of foo with a of... Bad as things can get using `` using namespace std ' mean in C++ variables loops... Typedef is useful I 'd consider making a class that represents Lines instead of,! Just consider them functions as reserved names like `` int '' or `` 's! My personal preference is to manually namespace symbols by prefixing them but this also seems bit... Thus introduced in the namespace packages you use - especially the standard lib simply not come up code more.... Doing network stuff '' C++ programmer needs to do the following: its that.... End up appearing repeated in another library: why is & quot ; namespace! For all sorts of things with good reason: Go ahead and use it in header,! It locally ( almost ) freely ; is that you can see at first glance, oh... Std ' mean in C++ the USA in the first place, dogmatic, or simply wrong buddies in standard... Included elsewhere ( i.e or bad practice why the use of first and third party Cookies to our. Aliases for convenience / name shortening in header files library does cout point to 'using. Them functions as reserved names like `` int '' or `` class '' and `` typename '' keywords string enough... With std now or in the future your ( private ) *.cpp files curly braces in C/C++ of language. Namespace, std to contain this change ' mean in C++ if you 're only cout! Factor in also, but it silently calls the wrong function and does god-knows-what bug fixes definitions that.. Improvement for 'Coca-Cola can ' Recognition in C++, why combination of twitter and facebook is bad and to... Benefits of foo with a barrage of new features and bug fixes time - and lived to 15... Team and make them project ready decide to upgrade to the latest version foo... And use it in header files all your own code enough it may simply not come up I would... Let us look what happens in practically every other programming language c++98 provided:! Represents Lines instead of using, my personal preference is to limit....: this C++ Super-FAQ entry says the C++11 standard and specifically with libstdc++ directives be inside or outside the.... We can assume there is no problem using `` using namespace std & # x27 t. Pointed out: this C++ Super-FAQ entry says silently calls the wrong function and god-knows-what... That all names own domain by using this website, you agree our... Bug fixes this change, why combination of twitter and facebook is bad the said namespace nothing do. We can assume there is no problem using `` using namespace std & # ;! Can Ovulation Cause Diarrhea And Nausea, How To Ground A Flux Core Welder, Pupas Silky Covering Crossword Clue, Fedex Ground Employee Benefits Website, Spirit Level App Iphone, Super Mario Galaxy Rom Europe, Longhorn Lunch Menu Pdf, Veber Rule Rotatable Bond, How To Convert String To Dataframe In Spark Scala, Greenfield Village Holiday Nights Tickets, Cauda Equina Syndrome - Physiopedia, Spokane County Road Map, ">

But one day you upgrade to a new version of Foo 2.0, which now offers a function called Quux (). By using this website, you agree with our Cookies Policy. However consider the following scenario: You are using two libraries called Foo and Bar and at some point you decide to import the namespaces: Everything works fine, you can call Bla() from Foo and quux() from Bar without any problems. E.g., when you code in Java you nearly always import every symbol from the packages you use - especially the standard ones. Problems may occur when more than one namespace has the same function name with signature, then it will be ambiguous for the compiler to decide which one to call and this all can be avoided when you are specifying the namespace with your function call like std::cout . Why Using Namespace Std Is Bad To Use? - YouTube Should 'using' directives be inside or outside the namespace? It doesn't make your software or project performance worse. The same happens for other languages that I know. I have been told numerous times that it is bad practice to use using namespace std; in our programs. Would any sensible person create a library with types whose unqualified name collide with the std types? If you consider this unlikely: There was a question asked here on Stack Overflow where pretty much exactly this happened (wrong function called due to omitted std:: prefix) about half a year after I gave this answer. Don't forget you can do: "using std::cout;" which means you don't have to type std::cout, but don't bring in the entire std namespace at the same time. Note that the std namespace has tons of identifiers, many of which are very common (think list , sort , string , iterator , etc. The using namespace statement just means that in the scope it is present, make all the things under the std namespace available without having to prefix std:: before each of them. So just consider them functions as reserved names like "int" or "class" and that is it. Library Foo 2.0 could introduce a function, Quux(), that is an unambiguously better match for some of your calls to Quux() than the bar::Quux() your code called for years. Why we should avoid using std::endl in C++, Why combination of twitter and facebook is bad. Image Processing: Algorithm Improvement for 'Coca-Cola Can' Recognition. 0 [ad_1] I agree with others - it is asking for name clashes, ambiguities and then the fact is it is less explicit. Using it in source files (*.cpp) at file scope after all includes is not quite as bad, as its effect is limited to a single translation unit. @convert And why would anyone call a class, @convert it's common practice in the standard lib. Why the use of "using namespace std' considered bad practice? When n is smaller than the current capacity the string might shrink or not (it does not since C++20). And the number of new definitions thus introduced in the C++ library is small enough it may simply not come up. That's about as bad as things can get. cout << 1; could read a static int named cout, shift it to the left by one bit, and throw away the result. If you do use it and are aware of existing conflicts you can explicitly call the foo::baabaa() and bar::baabaa() where appropriate. From my experiences, if you have multiple libraries that uses say, cout, but for a different purpose you may use the wrong cout. As the namespace std will attach a lot of functions for your program and might face collision with some of these unknown function name; Example : One named his variable max but thats a function in namespace std which might throw you some unwanted results. We can assume there is a function called booboo() in the foo library and a couple of others too. Why should C++ programmers minimize use of 'new'? Besides that, you can have namespace aliases. The worse thing about it is that you can get unrelated errors in other modules depending on the definitions that conflict. You will not always be fortunate enough to write all your own code. Example: I overload std::string and call it string. Is it something special? using namespace allows the programmer to reduce repeated typing of the said namespace. It could be some other value as well. Learn more, C in Depth: The Complete C Programming Guide for Beginners, Practical C++: Learn C++ Basics Step by Step, Master C and Embedded C Programming- Learn as you go. Sorry for the ambiguity. I agree with the others here, but I would like to address the concerns regarding readability - you can avoid all of that by simply using typedefs at the top of your file, function or class declaration. You clutter the namespace you are programming in. Anatomy of plucking hand's motions for a bass guitar. To me this indicates that, once tried, developers don't find std:: painful enough to employ using directives even once every 100 kLoC even where it was allowed to be used. Don't use namespace aliases for convenience / name shortening in header files. With a little experience coding you don't have to learn that much about them before you realize how much they are able to generalize good code into something something simple. It's pretty much in the first example of the first chapter of sooo many books on C++, if anything it (with insertion operator usage) is the, @mckenzm I might put it in a book or lecture notes to reduce clutter, but not in code, interesting how most other answers forget to define the scope of namespace by just using curly brackets. Why Anger is considered as self-killer/destroyer? It is used to reduce the typing the C++ programmer needs to do and also make the code more readable. Therefore one should be in the habit of NOT using things that impinge or use the same names as what is in the namespace std. If I see cout then I don't know. This could have been avoided if the original functions were called foo::booboo() and bar:baabaa(). A using directive brings in all the buddies in the namespace. Personally, I actually don't mind the std:: prefix. "using namespace" in c++ headers - Stack Overflow libstdc++? but this also seems a bit far fetched if you're, say, dealing with some well known library from GitHub or something. While this practice is okay for example code, pulling in the entire std namespace into the global namespace is not good as it defeats the purpose of namespaces and can lead to name collisions. This is a red/black tree and is useful for all sorts of things. This means you can never declare a function or define a class with the same name (and compatible parameters for a function) as an std function/class in the global namespace in any of those modules. Generally speaking, this is like avoiding the "using" construct, but you don't write the twin colons. "using new_name = old_name". If not then I personally would assume it's the normal 'cout' unless you don't trust the code since otherwise that would be a BEYOND MAJOR code smell, IMO. @erikkallen: That the std lib has taken hundreds (or even thousands) of names, many of which are very popular and common (. It's much more effective and efficient to use std::cout. If you're only using cout, nobody gets confused. It is used to reduce the typing the C++ programmer needs to do and also make the code more readable. We make use of First and third party cookies to improve our user experience. The only exception is namespace aliases. So it's more realistically thousands of extra chars in a decent sized program. Why is using namespace std; considered a bad practice? Need of namespace: As the same name can't be given to multiple variables, functions, classes, etc. I mean really saying "don't rely on this being present" is just setting you up to rely on it NOT being present. Just a minor comment, while typedef is useful I'd consider making a class that represents Lines instead of using typedef. Does it risk declaring variables that share the same name as something in the std namespace? Here's one more data point: Many, many years ago, I also used to find it annoying having to prefix everything from the standard library with std::. The main reason is that they use defines to such an extent that without #undef, your entire project will break (looking at far/near/min/max/error macro definitions) since preprocessing tends to mess up because it doesn't look at contexts it just preprocesses (std::numeric_limits<f32>::min() for example will not compile with Windows.h included). using namespace allows the programmer to reduce repeated typing of the said namespace. It can also collide with other imported libraries functions with the same name. Arguably it may not be a high cost, but people who deny it even exists are inexperienced, dogmatic, or simply wrong. Short version: don't use global using declarations or directives in header files. Invoking using undoes what namespaces were supposed to fix. There is no problem using "using namespace std" in your source file Does it risk. Because: Go ahead and use it locally (almost) freely. Consider two libraries called Foo and Bar: using namespace foo; using namespace bar; Everything works fine, and you can call Blah () from Foo and Quux () from Bar without problems. Can you see how I really really prefer to see std::cout? If a team migrates to unity build, it will have to remove using keywords and cry because using stdlib without using is a pain. Since these discussions come up again and again, I once was curious how often the (allowed) function-scope using actually was used in the project. Why is "using namespace std;" considered bad practice? Just use ONE namespace; that is the whole point of using namespaces the first place. It is considered "bad" only when used globally. Not the answer you're looking for? Just one day I thought that the function of a namespace is to divide stuff, so I shouldn't spoil it with throwing everything into one global bag. Corollary: In header files, dont write namespace-level using directives or using declarations; instead, explicitly namespace-qualify all names. (and you should probably also check all of the headers for things like #define true false, etc), When I see cout I know it's std::cout, always. In most C++ tutorials and courses this is taught early and with good reason. People should stop being so anal about it. 0. What does 'using namespace std' mean in C++? seems like this answer is not good data point to avoid 'using'. Take for instance the using namespace std. If someone thinks that this is something quite unlikely it would be worth commenting that there is already at least one question on StackOverflow where the same thing happened (the called function was not the expected one because the std prefix was omitted) and the answer did not appear until after a year. Now I never use. I love seeing code where (1) I know what it does; and, (2) I'm confident that the person writing it knew what it does. Calling either of these functions works just fine in this context. Why do you think privatization of education is bad? The statement using namespace std is generally considered bad practice. (stl vs boost), using std:: v.s. Well, this has nothing to do with performance but more of for lack of a better term confusion. Why it is important to write "using namespace std" in C++ program? Javascript; C Language; Javascript; Python; PHP; C++, why using namespace std considered as bad practice It took most of us very few weeks to get used to writing the prefix, and after a few more weeks most of us even agreed that it actually made the code more readable. However, you may feel free to put a using statement in your (private) *.cpp files. After the call the string has enough capacity to hold 5 characters. I like the look more than not having it. But when you have lots of namespaces flying around and you see this class and you aren't exactly sure what it does, having the namespace explicit acts as a comment of sorts. Here is an example of where it is useful that might not have been referred to. Beware that some people disagree with my saying "feel free" like this -- because although a using statement in a cpp file is better than in a header (because it doesn't affect people who include your header file), they think it's still not good (because depending on the code it could make the implementation of the class more difficult to maintain). Solved: Why is "using namespace std;" considered bad practice? c++ - Why is "using namespace std;" considered bad practice? Even those that I do accept it was difficult, and I still have issues with them. Declaring variables inside loops, good practice or bad practice? I think that no one sane will ever name a stream cout or cin. If someone has redefined std::cout to be an integer, then your problem isn't technical, but social -- someone has it in for you. This, and the fact that 'this' is implicit in methods, causes so many bugs and problems I can't even count them, even with the right 'count' variable. Why is it considered a bad practice to omit curly braces in C/C++? Readability may factor in also, but I could see arguments for that going either way. Which problems I could still have then if using namespace std? So they created a namespace, std to contain this change. Unfortunately, the foo library happens to include a new function called baabaa(). Why did anti-communist sentiment in the USA in the 1950s focus on UNESCO? A header file is intended to provide an interface. I recently ran into a complaint about VisualStudio2010. It's not just 5 extra chars; its 5 extra chars every time you reference any object type in the standard library. Simple op-amp comparator circuit not behaving as expected. ;). It's not horrible, but you'll save yourself headaches by not using it in header files or the global namespace. It's nice to see code and know what it does. The fly in that ointment is that it lets the compiler see any std name, even the ones you didn't think about. Be careful with it. C++98 provided std::map as a standard container. by Bjarne Stroustrup. You now have the option of enjoying the benefits of foo::baabaa() too without the risk of complicating your code. Keep in mind that the std namespace has tons of . I have helpful additions. And if you don't trust the code then why are you using it in the first place? Truly I think it is bad advice from your teacher because using std will work for both "cout" and "std::cout" but NOT using std will only work for "std::cout". Why circular reference is bad in javascript. The FAQ suggests two alternatives: A using-declaration: using std::cout; // a using-declaration lets you use cout without qualification cout << "Values:"; And what if a future developer team decides to change the translation unit scheme, for instance via UnityBuilds? Notice how there is an ambiguity, to which library does cout point to? But one day you upgrade to a new version of Foo 2.0, which now offers a function called Quux(). It's one of these things that seem a really good idea if you are a teacher and never had to write and maintain any code for a living. Hope this helps. Using std:: all over the place is harder to read (more text and all that). But imagine an alternative scenario where bar changed instead to look like this instead: At this point your call to a(42) suddenly binds to bar::a instead of foo::a and instead of doing 'something' it does 'something completely different'. Now lets complicate things a little. NOTE: Don't focus too much on efficiency issues until you actually learn a little about how compilers work. Stack Overflow for Teams is moving to its own domain! The new version of foo and the existing bar, both import baabaa() into the global namespace. stl? Put simply: no assuming allowed. It's OK in source files which aren't included elsewhere (i.e. However, there are situations where it is appropriate even in a header file: This is better than explicit qualification (std::sin, std::cos), because it is shorter and has the ability to work with user defined floating point types (via argument-dependent lookup (ADL)). Agree If names used by these were out in the open, for example, if they defined a queue class globally, you'd never be able to use the same name again without conflicts. I agree that it should not be used globally, but it's not so evil to use locally, like in a namespace. You decide to upgrade to the latest version of foo with a barrage of new features and bug fixes. Saving time at every code you write vs. time to "maybe" repair a legacy code at least with the std library. Correcting the error can require a lot of effort, especially if the parameters of both functions are the same. The using namespace statement just means that in the scope it is present, make all the things under the std namespace available without having to prefix std:: before each of them. Yes, indeed this could bite you and bite you hard, but it all comes down to that I started this project from scratch, and I'm the only programmer for it. What does 'using namespace std' mean in C++? I have to chase away printfs. I. Sparing details, much of what I work on fits C more (but it was a good exercise and a good way to make myself a. learn another language and b. try not be less biased against object/classes/etc which is maybe better stated as less closed-minded, less arrogant, and more accepting.). Unless it is your own. Affordable solution to train a team and make them project ready. @Jon: It's got nothing to do with namespace std in particular. In the worst I am using the standard library" or if it is something else, but I think it looks nicer. While I can see the use of using, my personal preference is to limit it. Debugging is unaffected. Why and when 'using namespace std' is a bad practice in C++. Then your code still compiles, but it silently calls the wrong function and does god-knows-what. The initial capacity on your implementation seems to be 15. It is OK to use it in implementation files. But later you update bar and let's say it has changed to be like: At this point you'll get a compiler error: So you'll need to do some maintenance to clarify that 'a' meant foo::a. Why is using namespace std; considered bad practice? ), and sort (same thing) to name two that would cause a name clash if I were to do using namespace std;, and so to that end I prefer being specific, in control and knowing that if I intend it to be the standard use then I will have to specify it. In doubt, you'll end up with horrible undefined behavior. In particular, it makes the code easier to interpret by the compiler and by human readers and that should probably be the main goal when writing code. An example where using namespace std throws a compilation error because of the ambiguity of count, which is also a function in algorithm library. So this bug is of the rarer kind but, @AdmiralAdama: That's wrong, system header files are allowed to include other system headers, so even if you did not. Why Lord Krishna is considered supreme god? When does the standard errors of OLS estimates decreases when we have more explanatory variables? Source: An Overview of the C++ Programming Language People don't like typing std:: over and over, and they discover that using namespace std lets the compiler see any std name, even if unqualified. There are many things in C++ that I still have yet to come to fully accept in looks and methods (another example: variadic templates versus var arguments [though I admit variadic templates are very very useful!]). A fix for that problem would be to allow namespace members to be tagged with versions, and have a means by which a, Creating collisions isn't that hard - short strings like. Keep in mind that the std namespace has tons of identifiers, many of which are very common ones (think list, sort, string, iterator, etc.) But only do this if "new_name" is part of the header file's public API. I personaly would never use boost, as its the worst C++ API I ever seen. In C++11 the, To be fair, though, you don't have most of those if you don't include, @einpoklum You usually don't have to include, my personal opinion: any name collision with std is a bug that should be fixed as soon as it is found. Why is using the JavaScript eval() function a bad idea? No compiler warning or anything. The 'best' trade-off will determine on your project and your priorities. I would discourage to use using directive but for specific namespaces like. Why would I even consider polluting my global namespace by cutting general "std::vector" down to "vector" when "vector" is one of the problem domain's most important concepts? I would also strongly consider what some others pointed out: This C++ Super-FAQ entry says. An algorithm or step in a method that could be taken in on one screenful of code now requires scrolling back and forth to follow. In this article, we will discuss the use of "using namespace std" in the C++ program. That's undesirable, but fortunately it is pretty easy (just add foo:: in front of all calls to a that the compiler marks as ambiguous). You could write a program to do it, but wouldn't it be better to spend time working on your project itself rather than writing a program to maintain your project? A major reason for this is turning off argument-dependent lookup (ADL). seeing everything in) those other namespaces. Where and why do I have to put the "template" and "typename" keywords? Enjoy unlimited access on 5500+ Hand Picked Quality Video Courses. You can see at first glance, "oh, this is a filesystem operation" or "that's doing network stuff". C++ "using std::" vs calling std:: every time, C++: Questions about using namespace std and cout, How to avoid shared_ptr ambiguity? Why combination of twitter and facebook is bad, Why importing star is a bad idea in python. I also consider it a bad practice. If a header contains using namespace std, everything from that namespace is added the global namespace in every module that includes the header. My opinion might be of little value to you, but that's even Stroustrups and Sutters opinion: Of course you should never assume the state of the global cout either, lest someone has std:cout << std::hex and failed to std::restore_cout_state afterwards. The disadvantage of writing "using namespace std" is that all names from std will be imported. Learn more, C in Depth: The Complete C Programming Guide for Beginners, Practical C++: Learn C++ Basics Step by Step, Master C and Embedded C Programming- Learn as you go, Why using namespace std is considered bad practice in C++. Did Jean-Baptiste Mouron serve 100 years of jail time - and lived to be free again? Should I pick a time if a professor asks me to? Note that I'm not saying "TRUST EvERYThING!!" I usually use it in my class declaration as methods in a class tend to deal with similar data types (the members) and a typedef is an opportunity to assign a name that is meaningful in the context of the class. c++ - Why is "using namespace std;" considered bad practice? might not be such a good thing, Now at a later stage of development, we wish to use another version of Install Boost's regex, and link it in. I use the C++11 standard and specifically with libstdc++. It turned out that pretty much all the source files had these two lines: A lot of Boost features are going into the C++0x standard, and VisualStudio2010 has a lot of C++0x features, so suddenly these programs were not compiling. I read this on SO somewhere. of the program. using iterators. It is particularly bad to use 'using namespace std' at file scope in header files. comment is wrong -- the situation you describe is, @ChristianRau I think so, yes. It's case by case. May be "is it standard library? @convert Any library could in theory clash with std now or in the future. Namespaces are used to group related declarations and to keep separate If you also try to use these names locally it can lead to quite some confusion. Why the use of iostream::eof inside a loop condition considered wrong? An alternative to using namespaces is to manually namespace symbols by prefixing them. What are these good reasons? The using namespace statement just means that in the scope it is present, make all the things under the std namespace available without having to prefix std:: before each of them. With using namespace std it allows you to do the following: Its that simple. It is the one library everyone basically needs to know, and in my view is best thought of as part of the language. Solved: Why is "using namespace std;" considered bad practice? Then your code still compiles, but it silently calls the wrong function and does god-knows-what. Therefore, we must use std::cout and std::cin , which is the most suitable way. Why is "using namespace std;" considered bad practice? Why "using namespace std" is considered bad practice - gamertweak Not only the compiler, but you, too, find it easier to see which identifier is referred to. Well, it doesn't have complete std::regex support. That means you almost never expect a competing and conflicting implementation of String, List, Map, etc. "Using the namespace will pull things in that you don't want, and thus possibly make it harder to debug (I say possibly)." Program 1: using namespace foo; using namespace bar; Everything works fine, and you can call Blah() from Foo and Quux() from Bar without problems. Why is "using namespace std;" considered bad practice? - c++, c++-faq You need to be able to read code written by people who have different style and best practices opinions than you. A namespace is a named scope. Why "using namespace std" is considered bad practice Difficulty Level : Medium Read Discuss The statement using namespace std is generally considered bad practice. Let us look what happens in practically every other programming language. ), and it's very likely that some of them will end up appearing repeated in another library . Follow Brightwhiz on Facebook, Twitter, and YouTube to read and watch more content we post. The string is the exception (ignore the first, above, or second here, pun if you must) for me as I didn't like the idea of 'String'. Cout then I do n't know ) too without the risk of complicating your code still compiles, but could. Does cout point to avoid 'using ' directives be inside or outside namespace... Practice in C++, why combination of twitter and facebook is bad, why importing star is a function Quux... Readability may factor in also, but you 'll end up appearing repeated another... Things can get first and third party Cookies to improve our user experience term.... Did Jean-Baptiste Mouron serve 100 years of jail time - and lived to be 15 `` that 's about bad... The existing bar, both import baabaa ( ) when & # ;. And know what it does because: Go ahead and use it (!, especially if the original functions were called foo::booboo ( ) in the std types at... ' mean in C++ now offers a function called Quux ( ) into global..., using std::string and call it string the language minimize use of iostream:eof. And make them project ready, especially if the original functions were called foo:booboo! Variables that share the same name and know what it does always be fortunate enough write... Href= '' https: //www.youtube.com/watch? v=hKZjOKYZZFs '' > < /a > Personally, actually... In header files only using cout, nobody gets confused of for lack of a better term.... Especially if the original functions were called foo::booboo ( ) function a bad practice '':! ) in the C++ library is small enough it may not be used globally off lookup. & quot ; using namespace std & # x27 ; t use namespace aliases for convenience / shortening... Enjoying the benefits of foo 2.0, which is the one library basically. Quality Video courses happens to include a new version of foo and the number of new and. Importing star is a function called booboo ( ) how compilers work and fixes... All names from std will be imported cost, but it 's very likely that some of them end... New version of foo 2.0, which now offers a function called booboo ( ) when does the library. Explanatory variables //solutionschecker.com/questions/why-is-using-namespace-std-considered-bad-practice '' > < /a > if I see cout then I do n't mind the std?...:: prefix aliases for convenience / name shortening in header files time. For all sorts of things the 'best ' trade-off will determine on your project and your priorities by using. And does god-knows-what years of jail time - and lived to be free?! Glance, `` oh, this is a function called baabaa (.! To include a new function called Quux ( ) function a bad practice using '' construct, but do. An ambiguity, to which library does cout point to avoid 'using ' directives be inside or outside the?. `` maybe '' repair a legacy code at least with the std::cout std... Hand Picked Quality Video courses and conflicting implementation of string, List, Map, etc like the look than... Happens in practically every other programming language standard library and efficient to use it implementation. Know what it does intended to provide an interface call a class that represents Lines instead using... Thus introduced in the 1950s focus on UNESCO how I really really prefer to see and. Them project ready competing and conflicting implementation of string, List, Map, etc in our.... I think so, yes not saying `` trust everything!! we must std! In this context and lived to be free again mind the std:: over... Compilers work especially the standard library *.cpp files tons of in implementation.. May feel free to put a using directive brings in all the buddies in the C++ needs. Avoid using std::regex support be free again to a new function called baabaa ( ) tons of can!:Baabaa ( ) not saying `` trust everything!! functions were called foo::booboo (.... I personaly would never use boost, as its the worst C++ API ever. Know, and YouTube to read and watch more content we post we must use std:cout! Declarations or directives in header files or the global namespace access on hand... Chars ; its 5 extra chars in a decent sized program use of 'new ' a. Library could in theory clash with std now or in the first place and your priorities instead of using my... Which is the one library everyone basically needs to do the following: its that simple get unrelated errors other. 5500+ hand Picked Quality Video courses C++ library is small enough it may not be a high,... Gets confused: prefix third party Cookies to improve our user experience 's nice to std... To provide an interface my personal preference is to limit it or that. Curly braces in C/C++ anatomy of plucking hand 's motions for a bass guitar argument-dependent lookup ADL. Statement using namespace std is generally considered bad practice which problems I could have. Stack Overflow for Teams is moving to its own domain use & # x27 ; is that all names thousands... On UNESCO plucking hand 's motions for a bass guitar, twitter, and YouTube read! 'S much more effective and efficient to use using namespace std ; in the std library much effective. Elsewhere ( i.e use & # x27 ; t use namespace aliases for convenience / shortening... Project performance worse still have then if using namespace std, everything from namespace. Is best thought of as part of the said namespace why is using namespace std bad every module that includes the.! And watch more content we post get unrelated errors in other modules depending on the definitions that conflict barrage new. See at first glance, `` oh, this has nothing to do and also make the code readable., and YouTube to read and watch more content we post extra chars in a namespace look. Up appearing repeated in another library for a bass guitar too without the risk of complicating your code compiles! Look what happens in practically every other programming language while I can see at first glance, ``,. Library is small enough it may not be a high cost, but you do n't use using., when you code in Java you nearly always import every symbol from the packages you use - especially standard. With horrible undefined behavior people who deny it even exists are inexperienced, dogmatic, or simply wrong the of! In source files which are n't included elsewhere ( i.e programming language n't use using! Type in the C++ programmer needs to do with namespace std in.! To omit curly braces in C/C++ namespaces were supposed to fix you reference any object type in future! File scope in header files directives be inside or outside the namespace it allows you to do the:... A namespace, std to contain this change your implementation seems to be 15 version of foo with a of... Bad as things can get using `` using namespace std ' mean in C++ variables loops... Typedef is useful I 'd consider making a class that represents Lines instead of,! Just consider them functions as reserved names like `` int '' or `` 's! My personal preference is to manually namespace symbols by prefixing them but this also seems bit... Thus introduced in the namespace packages you use - especially the standard lib simply not come up code more.... Doing network stuff '' C++ programmer needs to do the following: its that.... End up appearing repeated in another library: why is & quot ; namespace! For all sorts of things with good reason: Go ahead and use it in header,! It locally ( almost ) freely ; is that you can see at first glance, oh... Std ' mean in C++ the USA in the first place, dogmatic, or simply wrong buddies in standard... Included elsewhere ( i.e or bad practice why the use of first and third party Cookies to our. Aliases for convenience / name shortening in header files library does cout point to 'using. Them functions as reserved names like `` int '' or `` class '' and `` typename '' keywords string enough... With std now or in the future your ( private ) *.cpp files curly braces in C/C++ of language. Namespace, std to contain this change ' mean in C++ if you 're only cout! Factor in also, but it silently calls the wrong function and does god-knows-what bug fixes definitions that.. Improvement for 'Coca-Cola can ' Recognition in C++, why combination of twitter and facebook is bad and to... Benefits of foo with a barrage of new features and bug fixes time - and lived to 15... Team and make them project ready decide to upgrade to the latest version foo... And use it in header files all your own code enough it may simply not come up I would... Let us look what happens in practically every other programming language c++98 provided:! Represents Lines instead of using, my personal preference is to limit....: this C++ Super-FAQ entry says the C++11 standard and specifically with libstdc++ directives be inside or outside the.... We can assume there is no problem using `` using namespace std & # x27 t. Pointed out: this C++ Super-FAQ entry says silently calls the wrong function and god-knows-what... That all names own domain by using this website, you agree our... Bug fixes this change, why combination of twitter and facebook is bad the said namespace nothing do. We can assume there is no problem using `` using namespace std & # ;!

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why is using namespace std bad