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Not Just Expert Friendly
Check out this snippet from one of Bjarne Stroustrup’s CppCon keynote slides:
Now take a glance at one of Herb Sutter’s CppCon talk slides:
Bjarne’s talk was titled “Make Simple Tasks Simple” and Herb’s talk was tiled “Back To The Basics!: Modern C++ Style“. Since I abhor unessential complexity, I absolutely love the fact that these two dedicated gentlemen are spearheading the effort to evolve C++ in two directions simultaneously: increasing both expert-friendliness AND novice-friendliness.
By counterbalancing the introduction of advanced features like variadic templates and forwarding references with simpler features like range-for loops, nullptr, and brace-initialization, I think Bjarne and Herb (and perhaps other community members I don’t know about) are marvelously succeeding at the monumental task of herding cats. To understand what I mean, take a look at another one of Herb’s slides:
Do you see that teeny tiny dot at the end of the big arrow down on the lower right edge of the circle? Well, I don’t come anywhere close to qualifying for membership with the cats inside that dot… and I’d speculate that most advanced feature proposals and idiom ideas, whether they are understandable/teachable to mere mortals or not, originate from the really smart cats within that dot.
By gently but doggedly communicating the need for lowering the barriers to entry for potentially new C++ users while still navigating the language forward into unchartered waters, I’m grateful to Herb and Bjarne. Because of these men, the ISO C++ committee actually works – and it is indeed amazing for any committee to “work“.
Stopping The Spew!
Every C++ programmer has experienced at least one, and most probably many, “Template Spew” (TS) moments. You know you’ve triggered a TS moment when, just after hitting the compile button on a program the compiler deems TS-worthy, you helplessly watch an undecipherable avalanche of error messages zoom down your screen at the speed of light. It is rumored that some novices who’ve experienced TS for the very first time have instantaneously entered a permanent catatonic state of unresponsiveness. It’s even said that some poor souls have swan-dived off of bridges to untimely deaths after having seen such carnage.
Note: The graphic image that follows may be highly disturbing. You may want to stop reading this post at this point and continue to waste company time by surfing over to facebook, reddit, etc.
TS occurs when one tries to use a templated class object or function template with a template parameter type that doesn’t provide the behavior “assumed” by the class or function. TS is such a scourge in the C++ world that guru Scott Meyers dedicates a whole item in “Effective STL“, number 49, to handling the trauma associated with deciphering TS gobbledygook.
For those who’ve never seen TS output, here is a woefully contrived example:
The above example doesn’t do justice to the havoc the mighty TS dragon can wreak on the mind because the problem (std::vector<T> requires its template arg to provide a copy assignment function definition) can actually be inferred from a couple of key lines in the sea of TS text.
Ok, enough doom and gloom. Fear not, because help is on the way via C++14 in the form of “concepts lite“. A “concept” is simply a predicate evaluated on a template argument at compile time. If you employ them while writing a template, you inform the compiler of what kind(s) of behavior your template requires from its argument(s). As a use case illustration, behold this slide from Bjarne Stroustrup:
The “concept” being highlighted in this example is “Sortable“. Once the compiler knows that the sort<T> function requires its template argument to be “Sortable“, it checks that the argument type is indeed sortable. If not, the error message it emits will be something short, sweet, and to the point.
The concept of “concepts” has a long and sordid history. A lot of work was performed on the feature during the development of the C++11 specification. However, according to Mr. Stroustrup, the result was overly complicated (concept maps, new syntax, scope & lookup issues). Thus, the C++ standards committee decided to controversially sh*tcan the work:
C++11 attempt at concepts: 70 pages of description, 130 concepts – we blew it!
After regrouping and getting their act together, the committee whittled down the number of pages and concepts to something manageable enough (approximately 7 pages and 13 concepts) to introduce into C++14. Hence, the “concepts lite” label. Hopefully, it won’t be long before the TS dragon is relegated back to the dungeon from whence it came.
C++1y Automatic Type Deduction
The addition, err, redefinition of the auto keyword in C++11 was a great move to reduce code verbosity during the definition of local variables:
In addition to this convenient usage, employing auto in conjunction with the new (and initially weird) function-trailing-return-type syntax is useful for defining function templates that manipulate multiple parameterized types (see the third entry in the list of function definitions below).
In the upcoming C++14 standard, auto will also become useful for defining normal, run-of-the-mill, non-template functions. As the fourth entry below illustrates, we’ll be able to use auto in function definitions without having to use the funky function-trailing-return-type syntax (see the useless, but valid, second entry in the list).
For a more in depth treatment of C++11’s automatic type deduction capability, check out Herb Sutter’s masterful post on the new AAA (Almost Always Auto) idiom.
The Biggest Cheerleader
Herb Sutter is by far the biggest cheerleader for the C++ programming language – even more so than the language’s soft spoken creator, Bjarne Stroustrup. Herb speaks with such enthusiasm and optimism that it’s infectious.
In his talk at the recently concluded GoingNative2013 C++ conference, Herb presented this slide to convey the structure of the ISO C++ Working Group 21 (WG21):
On the left, we have the language core and language evolution working groups. On the right, we have the standard library working group.
But wait! That was the organizational structure as of 18 months ago. As of now, we have this decomposition:
As you can see, there’s a lot of volunteer effort being applied to the evolution of the language – especially in the domain of libraries. In fact, most of the core language features on the left side exist to support the development of the upcoming libraries on the right.
In addition to the forthcoming minor 2014 release of C++, which adds a handful of new features and fixes some bugs/omissions from C++11, the next major release is slated for 2017. Of course, we won’t get all of the features and libraries enumerated on the slide, but the future looks bright for C++.
The biggest challenge for Herb et al will be to ensure the conceptual integrity of the language as a whole remains intact in spite of the ambitious growth plan. The faster the growth, the higher the chance of the wheels falling off the bus.
“The entire system also must have conceptual integrity, and that requires a system architect to design it all, from the top down.” – Fred Brooks
“Who advocates … for the product itself—its conceptual integrity, its efficiency, its economy, its robustness? Often, no one.” – Fred Brooks
I’m not a fan of committees in general, but in this specific case I’m confident that Herb, Bjarne, and their fellow WG21 friends can pull it off. I think they did a great job on C++11 and I think they’ll perform just as admirably in hatching future C++ releases.
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