8 ms·

Bjarne Stroustrup Discusses C++

49 points by DmitryNovikov 13y ago

fhd2 13y ago
I'm sort of a C++/Stroustrup fan I guess, but this confused me: > C isn’t simpler for C-style programming than C++ is [...] Is Stroustrup really arguing that C is not simpler than C++? How can it not be simpler? C++ is essentially C with a ton of features added on top.
- deletes 13y ago
  C is not simpler as C++ as you can program( with a few minor differences ) in C++ using C style. In that case both are equally complex.
  - Sharlin 13y ago
    His point is that actually you don't want to write plain C - you want to pick some C++ features that considerably reduce the complexity of your code.
    - bstamour 13y ago
      Correct. Even if you simply changed all of your dynamic arrays to std::vectors, the code you write is now simpler, easier to reason about, and pretty much memory leak-free.
  - barrkel 13y ago
    Your statement that, effectively, C++ can do everything C can, plus more, has the direct logical implication that C++ is absolutely more complex, not equally complex. (FWIW, I don't fully agree with even that statement. C++ makes using e.g. enums with bitmasks much harder than C.)
- recentdarkness 13y ago
  He's just saying that if you write C in C++ it's as 'simple' as C itself. > C++ is essentially C with a ton of features added on top. You would just not use those 'ton of features on top'
  - fhd2 13y ago
    Even unused code arguably adds to the overall complexity. But maybe that's what he meant, yeah.
    - saurik 13y ago
      Unused code adds to the complexity of a project you manage. However, you did not write the compiler: you are writing a program using the compiler. You don't have any unused code: you just have access to features you will choose not to use.
- sz4kerto 13y ago
  The complexity of feature set of a language does not translate to complexity of programming in the given language. That's because if the problem is complex, then it might be easier to learn the more complex language features than solving the problem with simple language features.
  - fhd2 13y ago
    "Simple" and "easy" mean two very different things [1]. [1] http://www.johndcook.com/blog/2011/11/11/simple-versus-easy/ http://www.johndcook.com/blog/2011/11/11/simple-versus-easy/
- stephen_g 13y ago
  Those added features make for simpler code - I mean, almost anything that does string handling or requires dynamic arrays is way easier to do in C++.
  - Sharlin 13y ago
    Indeed. A simple language leads to complex code. And code complexity is the thing that needs to be avoided, not language complexity. You could write a Turing-complete language with a single instruction, for instance "subtract and branch if negative", and it would probably be the simplest language in the world, but writing anything nontrivial in it would be horribly complicated.
- eliasmacpherson 13y ago
  That whole paragraph is ridiculous. I'm commenting but really I should abstain because I feel I am lowering the tone with yet another great religious debate: C vs. C++. "No. C isn’t simpler for C-style programming than C++ is, nor “closer to the hardware,” nor indeed more efficient. I have yet to see a program that can be written better in C than in C++. I don’t believe such a program could exist. By “better” I mean smaller, more efficient, or more maintainable." Firstly, I'm sure what he's writing there is predicated on the C++ STL being available, the use of which will in turn increase compilation times, because there's a lot of templated code to compile. I cannot see how you would implement strlen or malloc in C++ (EDIT: as efficiently and/or) more efficiently than C, particularly when you take casting void into account. It's not a far stretch then to imagine writing drivers and so on, where idiomatic C++ would be a distraction compared to C. In the above his metrics, smaller, more efficient, more maintainable - I can't see any features that C++ has that will allow them to be proven true. Any program that has to interact with a C library - Stroustroup would suggest library then to be wrapped to make it behave according to C++ style - if so - if the code is just calling a few library functions, C will be shorter and better by all his metrics. The most convincing is maintainability, but C++ has many more ways to skin a cat than C, so where C had the overhead of understanding someone else's data structure, C++ pretty much does too.
  - stinos 13y ago
    [note: I use both C and C++ heavily, and I think you are interpreting Bjarne wrong here] the use of which will in turn increase compilation times sure, but that does not makes anything he says about it less true. You could even argue it has nothing to do with the discuession at all. I cannot see how you would implement strlen or malloc in C++ more efficiently than C He says "C is not more efficient" which means "C++ is as effecient, or more efficient". Which in turns means you are right, and he does not imply you are not (that's the "as efficient" part). Yeeha, you're both right, no need to start a war. Stroustroup would suggest library then to be wrapped to make it behave according to C++ style I'd rather think he'd suggest the library should have been written in C++ in the first place. Which is definitely shorter and better by his metrics. The most convincing is maintainability which again comes down to the "as efficient" part then.
stephen_g 13y ago
I know what he means about teaching - I do a lot of systems (embedded) stuff, and love (well written) C++, but the course I did on it at Uni was awful. If that had been my only exposure to C++, I never would have wanted to touch it again!
azov 13y ago
For the sake of balance, here is Yossi Kreinin's list of things that are wrong with C++: http://yosefk.com/c++fqa/defective.html http://yosefk.com/c++fqa/defective.html PS. One of my biggest gripes with C++ is the lack of uniformity. Not only the language itself has insane learning curve, every project does so many trivial and not-so-trivial things differently that it's like learning another language each time you dive into a new codebase. From code formatting, documentation, and source tree layout to error handling, libraries and build system - for something so huge and complicated as C++ there's an amazing number of batteries not included. Even the things that are supposed to be standard in theory are often not so in practice. Damn, there's still custom string classes in the APIs of many popular libraries - almost two decades after std::string and STL! PPS. And yes, there's a difference between having consistent conventions and trying to be perfect for everybody and everything.
- stinos 13y ago
  or as bjarne points out in the article There can be no programming language that is perfect for everybody and for everything. C++ doesn’t try to be everything for everybody, but it is rather good at the tasks for which it was designed – mostly systems programming, software infrastructure, and resource-constrained applications and Don’t just say “I want a GUI library” or “there is no proper support for task-based concurrency” or whatever. We know that.
  - pkolaczk 13y ago
    Yet, most operating systems have been written in pure C, resource constrained applications are still being written mostly in pure C or eventually C with classes (and mobile apps are not resource constrained apps anymore), and enterprise software infrastructure is written in a wide range of languages ranging from C, through Java to even Python. What C++ is mostly used for are games and desktop GUIs... :D
    - cageface 13y ago
      What C++ is mostly used for are games and desktop GUIs... Hardly. Just about every interesting native application is written in C++. Chrome, Photoshop, Cubase, Ableton Live, AutoCad, Java, V8, any AAA video game, etc. Whether you like C++ or not the fact remains that if you want to write an application of any complexity that really pushes the hardware it's just about your only reasonable choice. Maybe people still write kernels in C but kernels really aren't that complex compared to the applications they run.
nkurz 13y ago
Stroustrup says: The real novelty here is the return statement: Note that I return a potentially huge vector by value. In C++98, that would typically cause the copy of all elements of res, potentially many thousands of elements. That would be a serious performance bug. In C++11, vector has a “move constructor,” so that rather than copying elements, the representation of res (merely three pointers) is “stolen” for use in the caller and an empty vector is left behind. After all, we are just about to return from find_all() and won’t be able to use res again. Thus, returning a vector by value costs at most six word assignments independently of the number of elements. Move constructors is a simple facility available to every programmer and used by all standard-library containers implemented as handles. This allows us to return large objects from a function without messing around with memory management (explicitly) using pointers and free store. Are most C++ programmers excited by this? Is the idea that people should start writing code depending on this behind the scenes behaviour, or that we now have a way to speed up poorly written code? It feels like an awful lot of effort to avoid returning a pointer. And if I were actually worried about the performance, I wouldn't feel comfortable just hoping it happened. Is there any confirmation by the compiler that it handled this in the way the programmer wanted?
- detrino 13y ago
  The alternative to returning a vector by value would more likely be passing an empty vector by reference and then adding elements to it, then returning void. Returning a pointer instead (or unique_ptr) would be replacing value semantics with reference semantics which would be less efficient and inconsistent in interface. That's what move semantics bring to C++, consistent interfaces and efficiency.
  - textminer 13y ago
    I've basically freshly come to C++ in a work environment, and C++11 is all I've learned so far. Range-for loops and smart pointers and move semantics are wonderful. I still haven't adopted to a perfect idiom for calling functions, though: It's straightforward if I call a function and it returns a single object with move semantics. But what if I want to mutate multiple things with a function call (say, go through a vector and throw out indexes below a certain threshold, updating an unordered_map so as to specify the names and locations of certain columns). Do I return one, while changing the other by reference? Do I return a pair or a struct that only exists for me to quickly unpack? Do I make the function void and change both by reference?
z3phyr 13y ago
There are languages specially groomed to replace C++, like D and Rust, but they might never; Not in this decade. The day LLVM gets rewritten in Rust, that day Rust barely starts replacing C++.....

49 points by DmitryNovikov 13y ago

fhd2 13y ago

I'm sort of a C++/Stroustrup fan I guess, but this confused me: > C isn’t simpler for C-style programming than C++ is [...] Is Stroustrup really arguing that C is not simpler than C++? How can it not be simpler? C++ is essentially C with a ton of features added on top.

deletes 13y ago
C is not simpler as C++ as you can program( with a few minor differences ) in C++ using C style. In that case both are equally complex.
- Sharlin 13y ago
  His point is that actually you don't want to write plain C - you want to pick some C++ features that considerably reduce the complexity of your code.
  - bstamour 13y ago
    Correct. Even if you simply changed all of your dynamic arrays to std::vectors, the code you write is now simpler, easier to reason about, and pretty much memory leak-free.
- barrkel 13y ago
  Your statement that, effectively, C++ can do everything C can, plus more, has the direct logical implication that C++ is absolutely more complex, not equally complex. (FWIW, I don't fully agree with even that statement. C++ makes using e.g. enums with bitmasks much harder than C.)
recentdarkness 13y ago
He's just saying that if you write C in C++ it's as 'simple' as C itself. > C++ is essentially C with a ton of features added on top. You would just not use those 'ton of features on top'
- fhd2 13y ago
  Even unused code arguably adds to the overall complexity. But maybe that's what he meant, yeah.
  - saurik 13y ago
    Unused code adds to the complexity of a project you manage. However, you did not write the compiler: you are writing a program using the compiler. You don't have any unused code: you just have access to features you will choose not to use.
sz4kerto 13y ago
The complexity of feature set of a language does not translate to complexity of programming in the given language. That's because if the problem is complex, then it might be easier to learn the more complex language features than solving the problem with simple language features.
- fhd2 13y ago
  "Simple" and "easy" mean two very different things [1]. [1] http://www.johndcook.com/blog/2011/11/11/simple-versus-easy/ http://www.johndcook.com/blog/2011/11/11/simple-versus-easy/
stephen_g 13y ago
Those added features make for simpler code - I mean, almost anything that does string handling or requires dynamic arrays is way easier to do in C++.
- Sharlin 13y ago
  Indeed. A simple language leads to complex code. And code complexity is the thing that needs to be avoided, not language complexity. You could write a Turing-complete language with a single instruction, for instance "subtract and branch if negative", and it would probably be the simplest language in the world, but writing anything nontrivial in it would be horribly complicated.
eliasmacpherson 13y ago
That whole paragraph is ridiculous. I'm commenting but really I should abstain because I feel I am lowering the tone with yet another great religious debate: C vs. C++. "No. C isn’t simpler for C-style programming than C++ is, nor “closer to the hardware,” nor indeed more efficient. I have yet to see a program that can be written better in C than in C++. I don’t believe such a program could exist. By “better” I mean smaller, more efficient, or more maintainable." Firstly, I'm sure what he's writing there is predicated on the C++ STL being available, the use of which will in turn increase compilation times, because there's a lot of templated code to compile. I cannot see how you would implement strlen or malloc in C++ (EDIT: as efficiently and/or) more efficiently than C, particularly when you take casting void into account. It's not a far stretch then to imagine writing drivers and so on, where idiomatic C++ would be a distraction compared to C. In the above his metrics, smaller, more efficient, more maintainable - I can't see any features that C++ has that will allow them to be proven true. Any program that has to interact with a C library - Stroustroup would suggest library then to be wrapped to make it behave according to C++ style - if so - if the code is just calling a few library functions, C will be shorter and better by all his metrics. The most convincing is maintainability, but C++ has many more ways to skin a cat than C, so where C had the overhead of understanding someone else's data structure, C++ pretty much does too.
- stinos 13y ago
  [note: I use both C and C++ heavily, and I think you are interpreting Bjarne wrong here] the use of which will in turn increase compilation times sure, but that does not makes anything he says about it less true. You could even argue it has nothing to do with the discuession at all. I cannot see how you would implement strlen or malloc in C++ more efficiently than C He says "C is not more efficient" which means "C++ is as effecient, or more efficient". Which in turns means you are right, and he does not imply you are not (that's the "as efficient" part). Yeeha, you're both right, no need to start a war. Stroustroup would suggest library then to be wrapped to make it behave according to C++ style I'd rather think he'd suggest the library should have been written in C++ in the first place. Which is definitely shorter and better by his metrics. The most convincing is maintainability which again comes down to the "as efficient" part then.

stephen_g 13y ago

I know what he means about teaching - I do a lot of systems (embedded) stuff, and love (well written) C++, but the course I did on it at Uni was awful. If that had been my only exposure to C++, I never would have wanted to touch it again!

azov 13y ago

For the sake of balance, here is Yossi Kreinin's list of things that are wrong with C++: http://yosefk.com/c++fqa/defective.html http://yosefk.com/c++fqa/defective.html PS. One of my biggest gripes with C++ is the lack of uniformity. Not only the language itself has insane learning curve, every project does so many trivial and not-so-trivial things differently that it's like learning another language each time you dive into a new codebase. From code formatting, documentation, and source tree layout to error handling, libraries and build system - for something so huge and complicated as C++ there's an amazing number of batteries not included. Even the things that are supposed to be standard in theory are often not so in practice. Damn, there's still custom string classes in the APIs of many popular libraries - almost two decades after std::string and STL! PPS. And yes, there's a difference between having consistent conventions and trying to be perfect for everybody and everything.

stinos 13y ago
or as bjarne points out in the article There can be no programming language that is perfect for everybody and for everything. C++ doesn’t try to be everything for everybody, but it is rather good at the tasks for which it was designed – mostly systems programming, software infrastructure, and resource-constrained applications and Don’t just say “I want a GUI library” or “there is no proper support for task-based concurrency” or whatever. We know that.
- pkolaczk 13y ago
  Yet, most operating systems have been written in pure C, resource constrained applications are still being written mostly in pure C or eventually C with classes (and mobile apps are not resource constrained apps anymore), and enterprise software infrastructure is written in a wide range of languages ranging from C, through Java to even Python. What C++ is mostly used for are games and desktop GUIs... :D
  - cageface 13y ago
    What C++ is mostly used for are games and desktop GUIs... Hardly. Just about every interesting native application is written in C++. Chrome, Photoshop, Cubase, Ableton Live, AutoCad, Java, V8, any AAA video game, etc. Whether you like C++ or not the fact remains that if you want to write an application of any complexity that really pushes the hardware it's just about your only reasonable choice. Maybe people still write kernels in C but kernels really aren't that complex compared to the applications they run.

nkurz 13y ago

Stroustrup says: The real novelty here is the return statement: Note that I return a potentially huge vector by value. In C++98, that would typically cause the copy of all elements of res, potentially many thousands of elements. That would be a serious performance bug. In C++11, vector has a “move constructor,” so that rather than copying elements, the representation of res (merely three pointers) is “stolen” for use in the caller and an empty vector is left behind. After all, we are just about to return from find_all() and won’t be able to use res again. Thus, returning a vector by value costs at most six word assignments independently of the number of elements. Move constructors is a simple facility available to every programmer and used by all standard-library containers implemented as handles. This allows us to return large objects from a function without messing around with memory management (explicitly) using pointers and free store. Are most C++ programmers excited by this? Is the idea that people should start writing code depending on this behind the scenes behaviour, or that we now have a way to speed up poorly written code? It feels like an awful lot of effort to avoid returning a pointer. And if I were actually worried about the performance, I wouldn't feel comfortable just hoping it happened. Is there any confirmation by the compiler that it handled this in the way the programmer wanted?

detrino 13y ago
The alternative to returning a vector by value would more likely be passing an empty vector by reference and then adding elements to it, then returning void. Returning a pointer instead (or unique_ptr) would be replacing value semantics with reference semantics which would be less efficient and inconsistent in interface. That's what move semantics bring to C++, consistent interfaces and efficiency.
- textminer 13y ago
  I've basically freshly come to C++ in a work environment, and C++11 is all I've learned so far. Range-for loops and smart pointers and move semantics are wonderful. I still haven't adopted to a perfect idiom for calling functions, though: It's straightforward if I call a function and it returns a single object with move semantics. But what if I want to mutate multiple things with a function call (say, go through a vector and throw out indexes below a certain threshold, updating an unordered_map so as to specify the names and locations of certain columns). Do I return one, while changing the other by reference? Do I return a pair or a struct that only exists for me to quickly unpack? Do I make the function void and change both by reference?

z3phyr 13y ago

There are languages specially groomed to replace C++, like D and Rust, but they might never; Not in this decade. The day LLVM gets rewritten in Rust, that day Rust barely starts replacing C++.....