Has the STL changed much? - c++

I'm wanting to become conversant in the use of the Standard Template Library. If I come across a general reference or beginner's guide published around 1995-97, can I rely on the information in it? How much has STL changed in the last dozen years?

Yes! There are new additions. The TR1 update is now implemented in most environments.
Your older book is still useful to learn the basics. But you will want to find a reference for TR1 to learn about some very useful new features. In a couple of areas, the new features are preferred over older ones. (What comes to mind is bind1st and bind2nd functionality is fully encapsulated in the more general bind construct.)
In addition, there are the boost libraries. (boost.org) Boost is a a collection of libraries, some are very useful, others are obscure. Some of the features in TR1 came from boost, so there is some overlap. There is at least one good book about Boost out there.

Not a whole lot, if at all. The current standard was published in 1998.
cplusplus.com has a more up-to-date reference, which you can compare for yourself.
I'd recommend also that you get a copy of Scott Meyers' Effective STL.

I like the SGI reference to the STL
http://www.sgi.com/tech/stl
Which includes a set of resource for further reading
http://www.sgi.com/tech/stl/other_resources.html
I think that this documentation was done by the crater of the STL (could bee wrong on that).
But the STL has not changed since it was made official.
The new additions for TR1 are currently not officially available but will be part of the new standard. Though you can grab them via boost. Which is another set of libraries you should look at.

Related

Did Boost::algorithms get subsumed into standard libraries?

Starting in C++11 (I think) a lot of Boost functionality was available in the STL, or in an extension TR1 (again, if memory serves).
I'm struggling to tell specifically which things were and were not included in C++11 and later versions (and in MSVC++ versions).
Specifically this very old question about joining vector<string> has a nice Boost-based answer: https://stackoverflow.com/a/6334153/197229.
I don't want to add boost dependency to my project so - is this functionality now available in standard libraries?
boost::algorithm::join is not part of the C++ standard library. (nor something with equivalent functionality).
More generally, sometimes things are implemented in Boost.Algorithm and then proposed for standardization (Boyer-Moore, for example), and sometimes I implement things that have been added to the standard library in Boost.Algorithm for people who can't/won't use the latest C++ version (any_of, for example).
boost::algorithm::join has not made its way into the standard library as of yet. There is an open paper (N3594) to have it added to the library, but it is sitting in the Library Evolution working group currently.
You'll either need to use one of the other implementations from that Q&A pair or include boost.

The very first implementation of STL

I am very interested in seeing the very first implementation of C++ Standard Template Library. Well, it is for historical reasons. I am curious to see how the library evolved throughout the time.
What is the first version (implementation) of STL that is officially available? When and where it was published? How can I get it?
You can follow along with the development of Stepanov's thinking on generic programming at the site he's set up to collect his papers:
http://www.stepanovpapers.com/

Have I used STL? Or not?

I'm confused about some of the documentation at cplusplus.com. Have I used the standard template library with either of these two lines of code?
for (std::string::const_iterator it = str.begin(); l < data.size; ++it, ++l)
and
tile_tag(): distance(std::numeric_limits<int>::max()), dir(unknown_direction), used(false)
See:
http://www.cplusplus.com/reference/string/string/begin/
and
http://www.cplusplus.com/reference/std/limits/numeric_limits/
If I have used STL, how can I modify them to do what they do without STL?
Thanks!
EDIT: I guess this is OUR definition of STL: http://www.sgi.com/tech/stl/stl_index_cat.html
I don't see const_iterator...but I do see max. But is that the max I used?
Yes, you used it, since std::string alone is "part of the STL", but, more importantly, you are using the iterators, which are a distinctive trait of the STL.
Now, for the mandatory purists part: the STL was a library published by SGI and developed mainly by Alexander Stepanov. What I think you are referring to is "the part of the SGI STL which was later included into the standard with some minor modifications", i.e. all the generic containers/algorithms/iterators stuff.
The usage of the term "STL" for this stuff is tolerated, what is plain wrong, instead, is calling "STL" the whole C++ standard library (which includes a lot of other stuff, e.g. iostreams, locale, the library inherited from C, ...).
If I have used STL, how can I modify them to do what they do without STL?
Why would you want to do that? Anyhow, you have several options, that span from rewriting such classes and algorithms from scratch to using simpler data structures (e.g. C strings) reimplementing only the algorithms you need. Anyway, they both imply reinventing the wheel (and probably reinventing a square wheel), so I'd advise you against doing this unless you have a compelling reason.
EDIT: I guess this is OUR definition of STL: http://www.sgi.com/tech/stl/stl_index_cat.html
Are you sure? Almost no one today uses the SGI STL, generally you use the (more or less) equivalent portion of your C++ standard library (that, by the way, is what you are doing in your code, since you are getting everything from the std namespace).
I don't see const_iterator...
const_iterator is a typedef member of basic_string<char>, you find it in its page.
but I do see max. But is that the max I used?
No, it's not it, your max is not a global function, but a member of the std::numeric_limits template class. Such class do not come from the STL.
Does your code include the namespace std? Then yes, you have used the Standard library. How you can you modify your code to not use the Standard library? Why on earth would you want to? Implementations must provide it- that's why it's called Standard. But if you're truly insane and feel the need to not use it, then ... look up the documentation on what those functions and classes do and write your own replacement.
You have used the STL std::string and std::numeric_limits. I don't know why you would want to avoid using STL (perhaps homework?). You could use old style C strings with a char* and the macro definition MAX_INT from C limits.
What is this "STL" you speak of?
There was this thing that SGI developed in the mid 90s. Yeah, that's 15+ years ago. Older than the previous C++ standard. Back in the days when compilers like Turbo C++ and Borland C++ were best-of-breed; when people used the phrase "C with classes" unironically and without derision; when the idea of compiling C++ primarily by first cross-compiling to C was finally being abandoned; when exceptions were (at least in this context!) a new idea.
They called it "STL" for "standard template library", and they were doing a bunch of neat things with templates and developing new idioms. For its time, it was pretty revolutionary. So much so, in fact, that almost all of its stuff got officially accepted into the standard library with the 1999 standardization of the language. (Similarly, lots of Boost stuff - although nowhere near all; Boost is huge - has been added to the std namespace in the new standard.)
And that's where it died.
Unless you are specifically referring to a few oddball things like std::iota or lexicographical_compare_3way, it is not appropriate to speak of "the STL", and it hasn't been appropriate to speak of "the STL" for twelve years. That's an eternity in computer science terms. (But, hell, I still seem to keep hearing about new installations of Visual C++ 6.0, and some people using even older compilers...)
You're using the standard library of the C++ language. I guess you could write "SC++L" if you like, but that's a bit awkward, isn't it? I mean, no sane Java programmer would ever refer to the SJL, nor any Pythonista to the SPL. Why would you need jargon to talk about using the standard library of the language you are using?
This is what you're supposed to do by default, after all. Could you imagine writing code in C without malloc, strlen et. al.? Avoiding std::string in C++ would be just as silly. Sure, maybe you want to use C++ as a systems programming language. But really, the kinds of applications where you absolutely have to squeeze out every cycle (keep in mind that using std::string is often more efficient than naive string algorithms, and difficult to beat with hard work, because of the simple algorithmic benefits of caching the string length count and possibly over-allocating memory or keeping a cache for short strings) are generally not ones that involve string processing.
(Take it from me - I have several years' experience as a professional mobile game developer, dating to when phones were much, much less powerful: the standard approach to string processing is to redesign everything to need as little of it as possible. And even when you do have to assemble - and line-wrap - text, it was usually not worth optimizing anyway because the time the code spends on that is dwarfed by the time it takes to actually blit the characters to screen.)
"STL" can mean a number of things.
Formally, the name "STL" was only ever used for the library developed by Stepanov, and which is now hosted by SGI. The library consisted, roughly speaking, of containers (vector, list, deque, map, set and all those), iterators and algorithms (and a few other bits and pieces, such as allocators)
This library was adopted and adapted into the C++ standard library when the language was standardized in 1998. In this process, a number of changes were made: corners were cut, components were left out, in order to keep the library small, and to make it easy to swallow for the committee members. A number of changes in order for it to better interoperate with the rest of the standard library, or with the language itself, and certain parts of the existing standard library were modified to become a bit more STL-like.
Today, it's really not very useful to discuss the original STL. So when most C++ developers say "STL", they mean "the part of the C++ standard library that was created when the STL was adopted into the standard". In other words, all the container classes, the iterators and the algorithms in the standard library, are commonly called "STL", simply because they look a lot like the "original" STL, and they're a lot more relevant today than the original library.
But this also means that the term has become rather fluffy and vague. The std::string class was not a part of the original STL. But it was modifed to behave "STL-like". For example, it was given iterators, so that it can be used with the STL algorithms. Should it be considered a part of the STL? Maybe, maybe not.
And to forther confuse matters, the STL became fashionable after it was adopted into the language. Suddenly, people started talking about "STL-style". The Boost libraries, for example, are generally written in a very STL-like way, and some Boost libs have been adopted into the standard library in C++11. So should they now be considered part of the STL?
Probably not, but you could make a pretty good case that they should: that they follow the spirit of the STL, and if Stepanov had thought of them when he write the original STL library, maybe he'd have included them.
Except for a few purists, who think that everyone is better off if the term "STL" is used exclusively to refer to something that no one ever actually needs to refer to (the SGI library), and if we have no way to refer to the standard library subset that it spawned, pretty much any C++ developer can agree that if you've used the standard library containers OR the standard library iterators OR the standard library algorithms, then you have used the STL.
In your code I see an iterator. So yes, you've used at least a small corner of the STL.
But why does it matter?

Boost library acceptance in industry

I have seen lots of people suggesting the Boost library on Stack Overflow, so I am also thinking of learning it. But today I came across this link: http://google-styleguide.googlecode.com/svn/trunk/cppguide.xml#Boost
I wanted to know about its acceptance in industry at a broader level. My current company also doesn't allow me to use this so I am confused whether to look into this or not.
Parts of Boost library is currently being accepted into the Standard library for C++0x and it is regarded as one of the top libs with a high industry acceptance. I'm actually unaware of any other library getting accepted into the C++ Standard Library on such a large scale.
"Ten Boost libraries are already included in the C++ Standards Committee's Library Technical Report (TR1) and will be in the new C++0x Standard now being finalized. C++0x will also include several more Boost libraries in addition to those from TR1. More Boost libraries are proposed for TR2."
You should definately look into this. Don't go by Google or any other large institution. They generally have to work to a subset of any complex language like C++. Hence, they'll have restrictions on which parts they can use so that it's easier to hire and train engineers to use the code base.
Additionally, Boost leverages many aspects of the higher forms of functionality within C++, case in point template meta-programming. Boost provides for a safer, though bulkier, form of functions as first class objects. They add in a more powerful "bind" which works so well with the standard library that I'd be lost without it. Finally, they have in place tuples and hash tables, both fundamental datatypes in modern development libraries.
In short, I really can't name one reason why you wouldn't want to look at Boost, even just to learn something. It's peer reviewed and largely platform independent. The source code is a treasure trove of information and more advanced programming techniques.
I think the who is using boost web page speaks for itself. Notably: Adobe, McAfee, and Real Networks probably qualify as industry.
My current company also does not allow me
to use [boost]. So I am confused whether
to look into it or not.
You might want to dig a little further and find out why. As others have said, Boost is a fantastically useful set of open source and peer reviewed libraries of extremely high quality. Look at their development LOC chart for an idea how long and how much $$ it would cost your company to reinvent the wheel.

Why is the Loki library not more widely used?

The Loki library implements some very widely used concepts (smart pointer, visitor, factory, etc.). The associated book "Modern C++ Design" is often mentioned, but the library itself is not widely used. Why is that?
Most developers seem to prefer Boost. In particular, why do people often decide to use Boost's smart pointers rather than Loki's?
Loki is a research/proof-of-concept sort of thing. Alexandrescu pushes new ideas, other people adopt those for real world. Also boost::shared_ptr is almost literally in TR1.
Loki's suffers from being a good library touching on several functional areas (template metaprogamming support with a few specific applications: smart pointers, singletons, function objects, scope guards etc.), whereas boost is a collection of many libraries typically exhaustively covering each functional area and much more highly tuned for portability (first).
When 9 birds out of 10 can be killed with the same stone, many people just start with boost and fill in the gaps with third party libraries. It's very hard to compete with boost if you overlap. Because you won't overlap with much of boost, people will download/install boost anyway to get the other functionality, so unless you nail an area that boost is weak at - and the difference is significant to the project, they'll "settle" for boost there too.
Further, Alexandrescu made repeated attempts to get Loki included in boost, and some of the key boost authors just weren't cooperative. My personal view is that they want the more complete but much less user-friendly MPL to have more "market share": as authors of the library and the hard-copy books that are the only decent documentation (in stark contrast with most other boost libraries which have excellent online documentation), they do quite well out of this.
If anyone is offended by and disagrees with this analysis, I'm all ears.
Another practical issue with extremely parameterised code is that in large projects where different developers/teams work independently, they'll often end up using subtly different instantiations of the same template pretty arbitrarily. This makes it harder to pass values between those subsystems: the receiver may need to:
be parameterised (i.e. templated, and hence inline, which introduces compilation dependencies and slower builds in enterprise-scale systems)
provide some minimal coverage for all possible instantiations (e.g. checking error codes and expecting/handling exceptions)
working through some compile-time to run-time hand-over based on an abstract base accessor with implementations for each instantiation) which compromises some of the performance benefits of parameterisation
This is all possible, but it takes a great programmer to navigate the terrain.
You want to use a library that the next programmer is going to know and that is going to be well supported in the future - so you pick a major lib.
Because it's a major lib lots of people use it, so it becomes the default choice.
I actually prefer Loki's way of doing things and I have contributed to Loki myself a Decorator pattern which now sits in the tracker because the project as far as I know is no longer maintained.
I use boost shared_pointer just because it will be the standard very soon, I may dislike the fact that I can't customize it to act exactly the way I want it to act but I have to live with it.
Usage of the standard library is important as it keeps the code maintainable by other programmers. If it's open source and you want to experiment go ahead and use Loki. No one is stopping you.
Actually Windows Vista uses some of Loki's features.
I am guessing they are not using the redundant implementations of smart pointers and visitors.
Speaking as someone who's used quite a bit of the Boost library, and also looked at Loki more than once, the biggest problem was the sparsity of documentation. Also, Loki uses some of the hairiest bits of C++ templates. Exciting stuff, but also rather daunting.
I used Loki once for a little tool (basically an interpreter) and actually liked it. My coworkers were less enthusiastic about the library, so its use remained constrained to this small sub-project.