All of the Following Are Functions of Art Exceptã¢â‹
Modern C++: A Love/Hate Story
From an Intermediate'south Bespeak of View
It'south non just nigh operation!
Recently, I more frequently hear many say "C++ is merely about performance!". Is that it? I mean. It'south great to learn a performant¹ programming linguistic communication, but is it enough to prefer one language over another? And then, why non C, for instance. For me, personally, C++ is more than that—then much more.
For some C++ developers, it's somehow like beingness part of a cult or a religion. The matter, for many others, is that they love C++, but they cannot give a reason why. I used to have the same trouble, until I began to realize that in that location are many expert reasons to dearest C++, including:
- It's, of class, a very performant language. Non only because information technology compiles into machine lawmaking or STL is highly optimized, only it's due to the fact that modern C++ compilers are getting so smart that optimized C++ codes can easily compete expert C codes in speed.²
- Information technology'due south curtailed, yet productive. I of the most beautiful concepts in C++ is that anything other than primitive types is just a
class. There are nointerfaceorabstruseclasses in a particular fashion.³ All the varieties in abstract data types come from a single keyword,class.⁴ - It's powerful. I'chiliad not talking almost a low-level programming language that gives you the ultimate power of pointers. Information technology's a general purpose language equipped with all the tools you need to express what's in your listen. If you believe that C++ is simply good for system programming, just take a look at GitHub projects to see the broad range of fields that it has been used for.
- Information technology has a nice interaction with the OS, since all widely used Bone'southward are written in C or C++. It allows to utilize arrangement resources more efficiently.
- It's a mature programming linguistic communication. There are so many (by and large open up source) libraries around, and information technology has a large customs that its members humbly provide gratuitous tutorials and answers to your questions.
Merely the story does non end hither.
Y'all don't know C++!
Before moving forrad, I'd like to advise y'all to read "C++ Common Noesis", an splendid book written by Stephen Dewhurst virtually common idioms and mistakes near modern C++. Somewhere in the Preface, he states,
… I was engaged in conversation with a group of well-known C++ experts at a conference. There was a full general mantle or depression among these experts that modern C++ is so complex that the "average" programmer can no longer understand it.
So, the experts blame it for being too complex and not understandable. Yet, I think the language is not guilty by itself, but it'southward becuase often there'southward more than just one mode to solve a problem in C++ and unexperienced programmers unremarkably get dislocated almost which one is the best⁵. For example, to implement Strategy pattern, should someone use policy-based blueprint, or inheritance, or lambda functions, or even function pointers? It'due south a lack of knowledge about how to use language features.
I don't intend to go besides deep well-nigh design problems hither⁶, but in the following sections, I'm going to accost some of the near problematic idioms that every C++ programmer needs to concern in his career.
Templates are not templates!
One of the major differences betwixt C++ and the other OO programming languages is that templates in C++ are not basically codes. The standard specifies that the templates are instantiated⁷ by the compiler just when they're first used. Not agreement C++ templates and using them like the fashion they work in C# or Java, put the developer in a big problem.
This odd principle has made templates one of the most poweful features of the language. Templates make possible to write generic codes, as other OO programming languages does, and as well, allow another avant-garde feature of the linguistic communication, called meta programming. However, meta programming requires expertise and a good understanding of other principles like SFINAE.⁸
Also, information technology must be noted that meta programming is a technique that should not exist overused. Outset, it makes the code hard to understand and can cause more hurt rather than benefit. Second, it can easily push the compiler to its limits by significantly increasing retentivity usage and compile time.
Beware of raw pointers!
Nowadays, most modern programming languages benefit from a garbage collector at their runtime system. Garbage collectors are responsible for managing allocated memory for reference types, i.e., class objects. C++ lacks a garbage collector and uses a more than avant-garde principle called RAII, instead.⁹
In the garbage collected OO languages, objects are typically constructed with a new keyword (or a like arroyo), and the programmer doesn't need to worry almost the object destruction. Although C++ supports manual object lifetime direction using new and delete keywords, but information technology'southward considered a very bad do. Also, in C++, there's no bespeak to allocate an object on the heap, only when,
- The object size is unknown at kickoff, such as arrays and vectors.
- The object is besides large to be allocated on the stack.
- The object is intended to be passed to another thread in concurrent applications — however, there are workarounds to avoid it.
- Someone needs to employ runtime polymorphism, as unfortunately C++ requires object pointers for that.
Having said that, the programmer is encouraged to employ make_unique and make_shared functions for the heap allotment, whenever needed.
STL is a part of the language!
Although information technology'southward usually misbelieved, STL is not just a collection of data structures and algorithms written by expert compiler constructors — not anymore. In modern C++, the linguistic communication is getting more and more than tied to it.¹⁰
Just take a look at the standards. In C++11, there's a strict connectedness betwixt range-based for loops and iterators, and also, uniform initialization and initializer_list. And, there volition be more with upcoming standards. So, the developer is intended to learn STL well and use information technology regularly.
Avoid virtual as much equally yous tin!
When I was reading the well known GoF book, "Pattern Patterns", I was more curious about a single phrase, "Adopt composition over inheritance." Well, hopefully information technology must be but a design determination, I idea. But today, I run across that virtual polymorphism is the most hated characteristic of the C++ language — and it'south not difficult to understand why. First, it works only on object pointers, and second, the virtual function call is very slow, compared to the straight function call.¹¹
The rages over virtual functions are so loftier that I'd expect a big revolution anytime. Simply till that day, I suggest to avoid them equally much as yous tin. In that location are a handful of techniques to extend class behaviors, such equally policies, CRTP, and also composition. The skilful thing about the composition is that it works in runtime. So, it'd be meliorate to prefer composition over inheritance when runtime polymorphism is required.
Functions are not evil!
C++ is rather a multi-paradigm language than just a pure OO language. You are free to use structural, object-oriented and functional paradigms at the aforementioned time. So, when you only need a function, just define a function and don't carp encapsulating information technology in a class as it's mutual in other fully OO languages, like Java. Employ namespaces to categorize functions whenever needed.
Really, in my feel, functions and lambda functions can fifty-fifty lead to a clearer design in many applications which crave composable behaviors, and the blazon deduction works more intuitively with part templates.
Larn blazon deduction rules; and learn them well!
Every C++ programmer is pretty familiar with function overloading and determining which 1's chosen against passed arguments, I guess. The type deduction is very similar for template parameters and auto keyword, except that they obey more circuitous rules.¹²
Without having a good understanding of the blazon deduction rules, information technology'due south almost impossible to empathise modern C++ anymore. Besides, with C++xiv and C++17 standards being published, these rules are increasingly important to understand.
Use const and final; they're not only decorators!
Everyone can recall the time when macros were very popular for defining constants. It was believed that inlining characteristic of the macros makes the lawmaking a lot faster. Only mod compilers are fashion smarter than earlier, right?
With const yous give the compiler a hint that the value (or the reference) is non meant to exist inverse, so that the compiler can generate more efficient codes treating information technology. Just it'south not the finish of the story. It too prevents unexpected behaviors caused by sudden changes, which becomes more of import when writing concurrent applications. So, do consider using const, especially when handing over a reference to a class fellow member. And by the fashion, try not to utilise const_cast for the same reason.¹³
The last keyword is very much like const, except that it prevents a grade to be inherited or a virtual function to be overridden past kid classes. Its usage might be a little less obvious, but use it wherever appropriate.
The less known mutable keyword is also important to be noted here, because information technology behaves differently when used for class members and lambda functions. When used with a class, it denotes that a field doesn't impact the external visible state of the class, which merely ways that it's safe to modify a mutable field without worrying about changing the object'southward behavior, fifty-fifty if it's defined as const. On the other hand, decorating a lambda role, the mutable keyword removes the const qualification from parameters captured by copy.
Give the ownership away!
Move semantics are ane of the revolutionary changes in C++. Both move constructors and move operators eliminate a lot of unnecessary copies during assignments and passing arguments, leading to a more efficient code. Though, learning the the deviation between lvalue and rvalue concepts might be a footling confusing at first, but it'due south worth it.
However, motility semantics are not just about optimization. They really come up in handy when dealing with concurrency. Keeping shared states is ane of the biggest challenges in writing concurrent applications equally it requires concerning mutex, expressionless lock, etc. It'd be a lot easier to brand a copy or hand the ownership over with movement semantics if information technology's not needed anymore.
What's Adjacent
C++ linguistic communication is evolving very rapidly that makes it hard to follow all the changes up. This article tries to accost some of the significant issues that most programmers are dealing with them near modernistic C++, but it's non nigh enough. Any developer should take his/her time to read excellent textbooks provided by experts — some of them referenced here—to fully sympathize the right fashion to write a software in C++.
¹ Some English speakers may non like word performant, just I'thousand using it considering it's adequate among software developers.
² See Matt Godbolt's talk at CppCon 2017, "What Has My Compiler Done for Me Lately? Unbolting the Compiler's Lid"
³ Think of struct equally a course that all its members are public by default. Also, an interface is merely a class that contains no data members and all its methods are public and pure virtual.
⁴ I don't heed union, considering it'due south gradually getting depracated when the time goes by. Information technology's one of the C left-overs from the old by.
⁵ The word best is somewhat ambiguous here. It commonly means fastest execution among developers, merely also clearest and nigh adequate.
⁶ There are some nice literatures around, e.thou., "Modern C++ Design" by Andrei Alexandrescu, "Effective Modernistic C++" by Scott Meyers, and the Stephen Dewhurst's book.
⁷ Template instantiation is not coordinating to form instantiation. It means the compiler generates the actual lawmaking for a template.
⁸ For more information read "C++ Templates" past David Vandevoorde, and Nicolai Josuttis.
⁹ At that place are C++ libraries that mimic garbage collection, but as I said, it's not a part of the language or its runtime.
¹⁰ Really, I hate it, but this is the way it works.
¹¹ Calling a virtual function requires two retention lookups. Showtime to load virtual table, and second to load virtual part's address. However, the cost of virtual functions isn't actually the lookup of a function pointer in the virtual table, but that the indirect leap usually cannot be branch-predicted.
¹² Meet Scott Meyers's talk at CppCon 2014, "C++ Blazon Deduction and Why You lot Care"
¹³ On the other manus, volatile is the nearly misinterpreted keyword in C++. The life would be easier if yous forget nearly it completely.
Source: https://alirus.medium.com/modern-c-a-love-hate-story-937fe0e0aa77
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