Legendary C++ Programming Language


1.1.   Legendary C++ programming language

Finally here we are. The legendary C++ programming language which is one of the most used programming languages. It was developed by Bjarne Strostrup born on December 30, 1950. He was the Danish computer scientist, most notable for creation and development of the widely used C++ programming language.
Stroustrup began developing C++ in 1978 but back then it was called C with Classes. He also wrote what many consider to be the standard textbook for the language, The C++ Programming Language, which is now in its third edition. The text has been revised twice because of evolution of C++ programming language.
C++ (pronounced "see plus plus") is a statically typed, free-form, multi-paradigm, compiled, general-purpose programming language. It is regarded as an intermediate-level language, as it comprises a combination of both high-level and low-level language features. Developed by Bjarne Stroustrup starting in 1979 at Bell Labs, it adds object oriented features, such as classes, and other enhancements to the C programming language. Originally named C with Classes, the language was renamed C++ in 1983, as a pun involving the increment operator?
C++ is one of the most popular programming languages and is implemented on a wide variety of hardware and operating system platforms. As an efficient compiler to native code, its application domains include systems software, application software, device drivers, embedded software, high-performance server and client applications, and entertainment software such as video games. Several groups provide both free and proprietary C++ compiler software, including the GNU Project, Microsoft, Intel and Embarcadero Technologies. C++ has greatly influenced many other popular programming languages, most notably C# and Java. Other successful languages such as Objective-C use a very different syntax and approach to adding classes to C.
C++ is also used for hardware design, where the design is initially described in C++, then analyzed, architecturally constrained, and scheduled to create a register-transfer level hardware description language via high-level synthesis.
The language began as enhancements to C, first adding classes, then virtual functions, operator overloading, multiple inheritance, templates, and exception handling among other features. After years of development, the C++ programming language standard was ratified in 1998 as ISO/IEC 14882:1998. The standard was amended by the 2003 technical corrigendum, ISO/IEC 14882:2003. The current standard extending C++ with new features was ratified and published by ISO in September 2011 as ISO/IEC 14882:2011 (informally known as C++11).

1.1.1.                 History

Bjarne Stroustrup began his work on "C with Classes" in 1979. The idea of creating a new language originated from Stroustrup's experience in programming for his Ph.D. thesis. Stroustrup found that Simula had features that were very helpful for large software development, but the language was too slow for practical use, while BCPL was fast but too low-level to be suitable for large software development. When Stroustrup started working in AT&T Bell Labs, he had the problem of analyzing the UNIX kernel with respect to distributed computing. Remembering his Ph.D. experience, Stroustrup set out to enhance the C language with Simula-like features. C was chosen because it was general-purpose, fast, portable and widely used. Besides C and Simula, some other languages that inspired him were ALGOL 68, Ada, CLU and ML. At first, the class, derived class, strong type checking, inlining, and default argument features were added to C via Stroustrup's C++ to C compiler, Cfront. The first commercial implementation of C++ was released on 14 October 1985.
In 1983, the name of the language was changed from C with Classes to C++ (++ being the increment operator in C). New features were added including virtual functions, function name and operator overloading, references, constants, user-controlled free-store memory control, improved type checking, and BCPL style single-line comments with two forward slashes (//). In 1985, the first edition of The C++ Programming Language was released, providing an important reference to the language, since there was not yet an official standard. Release 2.0 of C++ came in 1989 and the updated second edition of The C++ Programming Language was released in 1991. New features included multiple inheritance, abstract classes, static member functions, const member functions, and protected members. In 1990, The Annotated C++ Reference Manual was published. This work became the basis for the future standard. Late feature additions included templates, exceptions, namespaces, new casts, and a Boolean type.
As the C++ language evolved, the standard library evolved with it. The first addition to the C++ standard library was the stream I/O library which provided facilities to replace the traditional C functions such as printf and scanf. Later, among the most significant additions to the standard library, was a large amount of the Standard Template Library.
C++ is sometimes called a hybrid language.
It is possible to write object oriented or procedural code in the same program in C++. This has caused some concern that some C++ programmers are still writing procedural code, but are under the impression that it is object oriented, simply because they are using C++. Often it is an amalgamation of the two. This usually causes most problems when the code is revisited or the task is taken over by another coder.
C++ continues to be used and is one of the preferred programming languages to develop professional applications.

1.1.2.                 Standard library

The 1998 ANSI/ISO C++ standard consists of two parts: the core language and the C++ Standard Library; the latter includes most of the Standard Template Library (STL) and a slightly modified version of the C standard library. Many C++ libraries exist that are not part of the standard, and, using linkage specification, libraries can even be written in languages such as BASIC, C, Fortran, or Pascal. Which of these are supported is compiler-dependent.
The C++ standard library incorporates the C standard library with some small modifications to make it optimized with the C++ language. Another large part of the C++ library is based on the STL. This provides such useful tools as containers (for example vectors and lists), iterators to provide these containers with array-like access and algorithms to perform operations such as searching and sorting. Furthermore (multi)maps (associative arrays) and (multi)sets are provided, all of which export compatible interfaces. Therefore it is possible, using templates, to write generic algorithms that work with any container or on any sequence defined by iterators. As in C, the features of the library are accessed by using the #include directive to include a standard header. C++ provides 105 standard headers, of which 27 are deprecated.
The STL was originally a third-party library from HP and later SGI, before its incorporation into the C++ standard. The main architect behind STL is Alexander Stepanov, who experimented with generic algorithms and containers for many years. When he started with C++, he finally found a language where it was possible to create generic algorithms (e.g. STL sort) that perform even better than e.g. the C standard library qsort, thanks to C++ features like using inlining and compile-time binding instead of function pointers. The standard does not refer to it as "STL", as it is merely a part of the standard library, but many people still use that term to distinguish it from the rest of the library (input/output streams, internationalization, diagnostics, the C library subset, etc.).
Most C++ compilers provide an implementation of the C++ standard library, including the STL. Compiler-independent implementations of the STL, such as STLPort, also exist. Other projects also produce various custom implementations of the C++ standard library and the STL with various design goals.

1.1.3.                 Language features

C++ inherits most of C's syntax. The following is Bjarne Stroustrup's version of the Hello world program that uses the C++ Standard Library stream facility to write a message to standard output:
# include <iostream>

int main()
{
   std::cout << "Hello, world!\n";
}
Within functions that define a non-void return type, failure to return a value before control reaches the end of the function results in undefined behavior (compilers typically provide the means to issue a diagnostic in such a case). The sole exception to this rule is the main function, which implicitly returns a value of zero1.1.   Basic input/output operations
In this lesson we will focus on standard C++ input and output options that will give you the necessary information of successful programming. This input and output commands are not that difficult, quite the opposite in Windows programming (visual programming) you won’t need it at all. C++ input/output operations revolve around the notation of a data stream, where you can insert data into an output stream or extract data from an input stream. In previous example you have used the cout command. This command is the standard output command by the ISO/IEC C++ standard. In that first example you have also used the command cin and that is the complementary input stream from the keyboard. The cout and cin are commands which are defined by the std name space.

1.1.4.                 The keyboard input

To obtain input in a C++ programming language you need to type a command cin, using the extraction operator for a stream, >>. To read two integer values from the keyboard into integer variables n1 and n2, you can write this statement:
std::cin >> n1 >> n2;
Or if you previously typed using namespace std; then just this:
cin >> n1 >> n2;
The extraction operator , > > , “ points ” in the direction that data flows — in this case, from cin to each of the two variables in turn. Any leading whitespace is skipped, and the first integer value you key in is read into n1. This is because the input statement executes from left to right. Any whitespace following num1 is ignored, and the second integer value that you enter is read into n2. There has to be some whitespace between successive values, though, so that they can be differentiated. The stream input operation ends when you press the Enter key, and execution then continues with the next statement. Of course, errors can arise if you key in the wrong data, but I will assume that you always get it right! Floating - point values are read from the keyboard in exactly the same way as integers, and of course, you can mix the two. The stream input and operations automatically deal with variables and data of any of the fundamental types. For example, in the statements,
int n1 = 0, n2 = 0;
double factor = 0.0;
std::cin > > n1 > > factor > > n2;
the last line will read an integer into n1, then a floating - point value into factor , and finally, an integer into n2 .

1.1.5.                 Output to the Command Line

You have already seen output to the command line, but I want to revisit it anyway. Writing information to the display operates in a complementary fashion to input. As you have seen, the standard output stream is called cout , and you use the insertion operator, < < , to transfer data to the output stream. This operator also points in the direction of data movement. You have already used this operator to output a text string between quotes. I can demonstrate the process of outputting the value of a variable with a simple program.

1.1.5.1.                      Example

Now you will write an input/output program so open a new project and name it InputOutput1. After you name the project click OK and be sure to select a Win32 Console Application. In the Win32 Application Wizard click Next and then Finish. Enter a following code:
// InputOutput1.cpp : Defines the entry point for the console application.
//
#include "stdafx.h"
#include <iostream>
using namespace std;
int _tmain(int argc, _TCHAR* argv[])
{
            int a = 5;
            int b = 6;
            cout << a << endl;
            cout << b << endl;
            cout << "You have written an example of input/outpu program."<<endl;
            return 0;
}

If you entered a given code correct than it won’t be an error debugging it. If however, your code is incorrect than you have to check the code manually or look for red underlined errors (syntax errors). After you debug your code press Ctrl+F5 simultaneously on your keyboard if your using the Visual Studio C++. The program should display the following window.
Let’s examine the code a little bit. First of all you have used the following STD libraries: stdafx.h and the iostream. These are the standard libraries defined by the ISO/IEC C++ standard. After that you have used the namespace std which contains the basic commands for input and output. Below the function main you have entered two integers (numbers) that is: a and b. You assigned numbers to them (a = 5, b = 6). Then you used basic command to output or present these numbers, and the following sentence “You have written an example of input/output program.”
1.1.6.                 Escape Sequences
When you write a character string between double quotes, you can include special character sequences called escape sequences in the string. The main function of the escape sequences is that they allow characters to be included in a string that otherwise could not be represented in the string, and the do this by escaping from the default interpretation of the characters. An escape sequence starts by the backslash character \, and the backslash character cues the compiler to interpret the character that follows in a special way.
Here is a list of all escape sequences and their function.
Escape sequence
The function of escape sequence
\a
Sounds a beep
\n
Newline
\'
Single quote
\\
Backslash
\b
Backspace
\t
Tab
\”
Double quote
\?
Question mark

Obviously, if you want to be able to include a backslash or a double quote as a character to appear a string, you must use the appropriate escape sequences to represent them. Otherwise, the backslash would be interpreted as the start of another escape sequence, and the double quote would indicate the end of the character string.

1.1.6.1.   Example of Escape Sequence

Open a new project, name it EscapeSequence and write or copy the following code:
// EscapeSequence.cpp : Defines the entry point for the console application.
//
#include "stdafx.h"
#include <iostream>
#include <iomanip>
using namespace std;
int _tmain(int argc, _TCHAR* argv[])
{
            char newline = '\n'; //NEWLINE ESCAPE SEQUENCE
            cout << newline;     //START ON A NEW LINE
            cout << "\" We\'ll make our escape in sequence\", she said.";
            cout << "\n\tThe program\'s over, it\'s time to make a beep.\a\a";
            cout << newline;        //START ON A NEW LINE
            return 0;
}

The first line in main() defines the variable newline and initializes it with a character defined by the escape sequence for a new line. You can then use newline instead of endl from the standard library. After writing newline to cout , you output a string that uses the escape sequences for a double quote ( \ “ ) and a single quote ( \' ). You don ’ t have to use the escape sequence for a single quote here because the string is delimited by double quotes, and the compiler will recognize a single quote character as just that, and not a delimiter. You must use the escape sequences for the double quotes in the string, though. The string starts with a newline escape sequence followed by a tab escape sequence, so the output line is indented by the tab distance. The string also ends with two instances of the escape sequence for abeep, so you should hear a double beep from your PC ’ s speaker.

1.1.6.1. Operators and operator overloading

Operators that cannot be overloaded
Operator         Symbol
Scope resolution operator      ::
Conditional operator  ?:
dot operator    .
Member selection operator     .*
"sizeof" operator         sizeof
"typeid" operator        typeid
C++ provides more than 35 operators, covering basic arithmetic, bit manipulation, indirection, comparisons, logical operations and others. Almost all operators can be overloaded for user-defined types, with a few notable exceptions such as member access (. and .*) as well as the conditional operator. The rich set of overloadable operators is central to using C++ as a domain-specific language. The overloadable operators are also an essential part of many advanced C++ programming techniques, such as smart pointers. Overloading an operator does not change the precedence of calculations involving the operator, nor does it change the number of operands that the operator uses (any operand may however be ignored by the operator, though it will be evaluated prior to execution). Overloaded "&&" and "||" operators lose their short-circuit evaluation property.

1.1.6.2.Templates

C++ templates enable generic programming. C++ supports both function and class templates. Templates may be parameterized by types, compile-time constants, and other templates. C++ templates are implemented by instantiation at compile-time. To instantiate a template, compilers substitute specific arguments for a template's parameters to generate a concrete function or class instance. Some substitutions are not possible; these are eliminated by an overload resolution policy described by the phrase "Substitution failure is not an error" (SFINAE). Templates are a powerful tool that can be used for generic programming, template metaprogramming, and code optimization, but this power implies a cost. Template use may increase code size, since each template instantiation produces a copy of the template code: one for each set of template arguments. This is in contrast to run-time generics seen in other languages (e.g. Java) where at compile-time the type is erased and a single template body is preserved.
Templates are different from macros: while both of these compile-time language features enable conditional compilation, templates are not restricted to lexical substitution. Templates are aware of the semantics and type system of their companion language, as well as all compile-time type definitions, and can perform high-level operations including programmatic flow control based on evaluation of strictly type-checked parameters. Macros are capable of conditional control over compilation based on predetermined criteria, but cannot instantiate new types, recurse, or perform type evaluation and in effect are limited to pre-compilation text-substitution and text-inclusion/exclusion. In other words, macros can control compilation flow based on pre-defined symbols but cannot, unlike templates, independently instantiate new symbols. Templates are a tool for static polymorphism (see below) and generic programming.
In addition, templates are a compile time mechanism in C++ that is Turing-complete, meaning that any computation expressible by a computer program can be computed, in some form, by a template metaprogram prior to runtime.
In summary, a template is a compile-time parameterized function or class written without knowledge of the specific arguments used to instantiate it. After instantiation, the resulting code is equivalent to code written specifically for the passed arguments. In this manner, templates provide a way to decouple generic, broadly applicable aspects of functions and classes (encoded in templates) from specific aspects (encoded in template parameters) without sacrificing performance due to abstraction.

1.1.6.3. Objects

C++ introduces object-oriented programming (OOP) features to C. It offers classes, which provide the four features commonly present in OOP (and some non-OOP) languages: abstraction, encapsulation, inheritance, and polymorphism. One distinguishing feature of C++ classes compared to classes in other programming languages is support for deterministic destructors, which in turn provide support for the Resource Acquisition is Initialization concept.

1.1.6.4.Encapsulation

Encapsulation is the hiding of information in order to ensure that data structures and operators are used as intended and to make the usage model more obvious to the developer. C++ provides the ability to define classes and functions as its primary encapsulation mechanisms. Within a class, members can be declared as either public, protected, or private in order to explicitly enforce encapsulation. A public member of the class is accessible to any function. A private member is accessible only to functions that are members of that class and to functions and classes explicitly granted access permission by the class ("friends"). A protected member is accessible to members of classes that inherit from the class in addition to the class itself and any friends.
The OO principle is that all of the functions (and only the functions) that access the internal representation of a type should be encapsulated within the type definition. C++ supports this (via member functions and friend functions), but does not enforce it: the programmer can declare parts or all of the representation of a type to be public, and is allowed to make public entities that are not part of the representation of the type. Therefore, C++ supports not just OO programming, but other weaker decomposition paradigms, like modular programming.
It is generally considered good practice to make all data private or protected, and to make public only those functions that are part of a minimal interface for users of the class. This can hide the details of data implementation, allowing the designer to later fundamentally change the implementation without changing the interface in any way.

1.1.6.5.Inheritance

Inheritance allows one data type to acquire properties of other data types. Inheritance from a base class may be declared as public, protected, or private. This access specifier determines whether unrelated and derived classes can access the inherited public and protected members of the base class. Only public inheritance corresponds to what is usually meant by "inheritance". The other two forms are much less frequently used. If the access specifier is omitted, a "class" inherits privately, while a "struct" inherits publicly. Base classes may be declared as virtual; this is called virtual inheritance. Virtual inheritance ensures that only one instance of a base class exists in the inheritance graph, avoiding some of the ambiguity problems of multiple inheritance.
Multiple inheritance is a C++ feature not found in most other languages, allowing a class to be derived from more than one base classes; this allows for more elaborate inheritance relationships. For example, a "Flying Cat" class can inherit from both "Cat" and "Flying Mammal". Some other languages, such as C# or Java, accomplish something similar (although more limited) by allowing inheritance of multiple interfaces while restricting the number of base classes to one (interfaces, unlike classes, provide only declarations of member functions, no implementation or member data). An interface as in C# and Java can be defined in C++ as a class containing only pure virtual functions, often known as an abstract base class or "ABC". The member functions of such an abstract base class are normally explicitly defined in the derived class, not inherited implicitly. C++ virtual inheritance exhibits an ambiguity resolution feature called dominance.

1.1.6.6.  Polymorphism

Polymorphism enables one common interface for many implementations, and for objects to act differently under different circumstances.
C++ supports several kinds of static (compile-time) and dynamic (run-time) polymorphisms. Compile-time polymorphism does not allow for certain run-time decisions, while run-time polymorphism typically incurs a performance penalty.

1.1.6.7.Static polymorphism

Function overloading allows programs to declare multiple functions having the same name (but with different arguments). The functions are distinguished by the number or types of their formal parameters. Thus, the same function name can refer to different functions depending on the context in which it is used. The type returned by the function is not used to distinguish overloaded functions and would result in a compile-time error message.
When declaring a function, a programmer can specify for one or more parameters a default value. Doing so allows the parameters with defaults to optionally be omitted when the function is called, in which case the default arguments will be used. When a function is called with fewer arguments than there are declared parameters, explicit arguments are matched to parameters in left-to-right order, with any unmatched parameters at the end of the parameter list being assigned their default arguments. In many cases, specifying default arguments in a single function declaration is preferable to providing overloaded function definitions with different numbers of parameters.
Templates in C++ provide a sophisticated mechanism for writing generic, polymorphic code. In particular, through the Curiously Recurring Template Pattern, it's possible to implement a form of static polymorphism that closely mimics the syntax for overriding virtual functions. Since C++ templates are type-aware and Turing-complete, they can also be used to let the compiler resolve recursive conditionals and generate substantial programs through template metaprogramming. Contrary to some opinion, template code will not generate a bulk code after compilation with the proper compiler settings.

1.1.6.8. Dynamic polymorphism

Variable pointers (and references) to a base class type in C++ can refer to objects of any derived classes of that type in addition to objects exactly matching the variable type. This allows arrays and other kinds of containers to hold pointers to objects of differing types. Because assignment of values to variables usually occurs at run-time, this is necessarily a run-time phenomenon.
C++ also provides a dynamic_cast operator, which allows the program to safely attempt conversion of an object into an object of a more specific object type (as opposed to conversion to a more general type, which is always allowed). This feature relies on run-time type information (RTTI). Objects known to be of a certain specific type can also be cast to that type with static_cast, a purely compile-time construct that is faster and does not require RTTI.

1.1.3.9. Virtual member functions

Ordinarily, when a function in a derived class overrides a function in a base class, the function to call is determined by the type of the object. A given function is overridden when there exists no difference in the number or type of parameters between two or more definitions of that function. Hence, at compile time, it may not be possible to determine the type of the object and therefore the correct function to call, given only a base class pointer; the decision is therefore put off until runtime. This is called dynamic dispatch. Virtual member functions or methods[31] allow the most specific implementation of the function to be called, according to the actual run-time type of the object. In C++ implementations, this is commonly done using virtual function tables. If the object type is known, this may be bypassed by prepending a fully qualified class name before the function call, but in general calls to virtual functions are resolved at run time.
In addition to standard member functions, operator overloads and destructors can be virtual. A general rule of thumb is that if any functions in the class are virtual, the destructor should be as well. As the type of an object at its creation is known at compile time, constructors, and by extension copy constructors, cannot be virtual. Nonetheless a situation may arise where a copy of an object needs to be created when a pointer to a derived object is passed as a pointer to a base object. In such a case, a common solution is to create a clone() (or similar) virtual function that creates and returns a copy of the derived class when called.
A member function can also be made "pure virtual" by appending it with = 0 after the closing parenthesis and before the semicolon. A class containing a pure virtual function is called an abstract data type. Objects cannot be created from abstract data types; they can only be derived from. Any derived class inherits the virtual function as pure and must provide a non-pure definition of it (and all other pure virtual functions) before objects of the derived class can be created. A program that attempts to create an object of a class with a pure virtual member function or inherited pure virtual member function is ill-formed.

1.1.7.Parsing and processing C++ source code

It is relatively difficult to write a good C++ parser with classic parsing algorithms such as LALR(1).[32] This is partly because the C++ grammar is not LALR. Because of this, there are very few tools for analyzing or performing non-trivial transformations (e.g., refactoring) of existing code. One way to handle this difficulty is to choose a different syntax. More powerful parsers, such as GLR parsers, can be substantially simpler (though slower).
Parsing (in the literal sense of producing a syntax tree) is not the most difficult problem in building a C++ processing tool. Such tools must also have the same understanding of the meaning of the identifiers in the program as a compiler might have. Practical systems for processing C++ must then not only parse the source text, but be able to resolve for each identifier precisely which definition applies (e.g. they must correctly handle C++'s complex scoping rules) and what its type is, as well as the types of larger expressions.
Finally, a practical C++ processing tool must be able to handle the variety of C++ dialects used in practice (such as that supported by the GNU Compiler Collection and that of Microsoft's Visual C++) and implement appropriate analyzers, source code transformers, and regenerate source text. Combining advanced parsing algorithms such as GLR with symbol table construction and program transformation machinery can enable the construction of arbitrary C++ tools.

1.1.7.1.Compatibility


Producing a reasonably standards-compliant C++ compiler has proven to be a difficult task for compiler vendors in general. For many years, different C++ compilers implemented the C++ language to different levels of compliance to the standard, and their implementations varied widely in some areas such as partial template specialization. Recent releases of most popular C++ compilers support almost all of the C++ 1998 standard.
In order to give compiler vendors greater freedom, the C++ standards committee decided not to dictate the implementation of name mangling, exception handling, and other implementation-specific features. The downside of this decision is that object code produced by different compilers is expected to be incompatible. There were, however, attempts to standardize compilers for particular machines or operating systems (for example C++ ABI), though they seem to be largely abandoned now.

1.1.7.2. Exported templates

One particular point of contention is the export keyword, intended to allow template definitions to be separated from their declarations. The first widely available compiler to implement export was Comeau C/C++, in early 2003 (five years after the release of the standard); in 2004, the beta compiler of Borland C++ Builder X was also released with export. Both of these compilers are based on the EDG C++ front end. Other compilers such as GCC do not support it at all. Beginning ANSI C++ by Ivor Horton provides example code with the keyword that will not compile in most compilers, without reference to this problem. Herb Sutter, former convener of the C++ standards committee, recommended that export be removed from future versions of the C++ standard. During the March 2010 ISO C++ standards meeting, the C++ standards committee voted to remove exported templates entirely from C++11, but reserve the keyword for future use.

1.1.7.3.With C

C++ is often considered to be a superset of C, but this is not strictly true. Most C code can easily be made to compile correctly in C++, but there are a few differences that cause some valid C code to be invalid or behave differently in C++.
One commonly encountered difference is that C allows implicit conversion from void* to other pointer types, but C++ does not. Another common portability issue is that C++ defines many new keywords, such as new and class, that may be used as identifiers (e.g. variable names) in a C program.
Some incompatibilities have been removed by the 1999 revision of the C standard (C99), which now supports C++ features such as line comments (//), and mixed declarations and code. On the other hand, C99 introduced a number of new features that C++ did not support, such as variable-length arrays, native complex-number types, designated initializers, and compound literals. However, at least some of the C99-introduced features were included in the subsequent version of the C++ standard, C++11:
  • C99 preprocessor (including variadic macros, wide/narrow literal concatenation, wider integer arithmetic)
  • _Pragma()
  • long long
  • __func__
  • Headers:
    • cstdbool (stdbool.h)
    • cstdint (stdint.h)
    • cinttypes (inttypes.h).

In order to intermix C and C++ code, any function declaration or definition that is to be called from/used both in C and C++ must be declared with C linkage by placing it within an extern "C" {/*...*/} block. Such a function may not rely on features depending on name mangling (i.e., function overloading).
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