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1. Top results related to what are the function of dictionary in c code

   • What are the benefits of function pointers in C?

     Top Answer

     Answered Jul 19, 2017 · 3 votes

     • Same as regular typdefs, incredibly useful for 2 and 4. Instead of typing the whole thing, you can now use myFuncDef
     • A function declaration for a function that recieves a function pointer. A function that takes a function pointer of 1. would thus look int add2to3(myFuncDef functionPtr);
     • -
     • A function that takes an int and (probably based on that) returns you a function pointer. Using the typedef it would have looked like myFuncDef functionFactory(int n);

     Without typedefs these chains of pointers to pointers could get incredibly long as can be seen in this question: C syntax for functions returning function pointers

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   • What are the pros and cons of using extern variables in C in production code?

     Top Answer

     Answered Jul 11, 2019 · 6 votes

     One can share a variable between files in (at least) four ways. You already mentioned two of them:

     • using extern: it will be a global variable, anyone will be able to modify it, not thread-safe; the use of global variables should be minimized;
     • passing a pointer to the the variable: it will provide read / write access to the variable;
     • passing the value of the variable: provides read-only access to the variable;
     • using an access function.

     The function can be as simple as:

     float read_speed(){ return speed;}-

     If the variable needs to be modified also, another function can be provided:

     void write_speed(float new_speed){ speed = new_speed;}-

     The advantage of using access functions is that it separates the variable from the other files. If needed, you can provide several functions for the same variable, for different needs.

     The cost is that code will increase a little and speed will decrease lightly.

     Compare:

     float read_speed_mph(); // get speed in miles per hourfloat read_speed_mps(); // get speed in meters per second-

     They both return the same speed, expressed in different units. The body of the functions will make the right calculation to provide the correct value, while the variable will remain unmodified.

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     2/5

   • What are the principles of organizing C++ code in Visual Studio?

     Top Answer

     Answered Feb 09, 2016 · 1 votes

     The basic rule is: A project results in a single output file [1].

     If you want to package building blocks into static libraries, create a project for each one.

     Unit test are separate from the code, so it's common to see a "foo" and a "foo test" project side by side.

     With respect to your small building blocks, I use this guideline: If it is closely enough related to be put in the same folder, it is closely enough related to be put in the same project.

     And managing a ton of small projects is incredibly frustrating. They each have a million settings and definitions (under multiple configurations and platforms...) that are a real pain to transfer from one project to the other.

     Property pages are intended to solve this problem. Just define a property page containing related settings and definitions, and it becomes as easy as adding the property page to a new project.

     As each project can pull its settings from multiple property pages, you can group them into logical groups. As an example: a "unit test" property page with all settings related to your unit test framework.

     To create property page in Visual Studio 2015: in the View menu, there is an option "Property Manager". You get a different tree view of your solution, with the projects, then the configurations, and then all the property pages for that project+configuration combination. The context menu for the configuration has an option to create a new property page or to add an existing one.

     [1] Although it is common to have the Release configuration result in foo.dll and Debug configuration in food.dll, so they can exist next to each other without resorting to the Debug/ and Release/ folders. In the General properties, set the TargetName to "$(ProjectName)d" (for Debug configuration) and remove the "$(Configuration)" from the OutputDirectory (for all configurations) to achieve this.

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   • What are the semantics of function pointers with empty parentheses in each C standard?

     Top Answer

     Answered Mar 25, 2018 · 2 votes

     N1570 6.11.6:

     The use of function declarators with empty parentheses (not prototype-format parameter type declarators) is an obsolescent feature.

     This same wording appears in the 1990, 1999, and 2011 editions of the ISO C standard. There has been no change. The word obsolescent says that the feature may be removed in a future edition of the Standard, but so far the committee has not done so. (Function pointer declarations are just one of several contexts where function declarators can appear.)

     The Introduction section of the C standard explains what obsolescent means:

     Certain features are obsolescent, which means that they may be considered for withdrawal in future revisions of this International Standard. They are retained because of their widespread use, but their use in new implementations (for implementation features) or new programs (for language [6.11] or library features [7.31]) is discouraged.

     A call to a function declared with an old-style declarator is still required to pass the correct number and type(s) of arguments (after promotion) as defined by the function's actual definition. A call with incorrect arguments has undefined behavior, which means that the compiler is not required to diagnose the error; the burden is entirely on the programmer.

     This is why prototypes were introduced, so that the compiler could check correctness of arguments.

     On an i386 system with GCC, “extra” arguments passed in a call to an empty-parentheses-type’d function pointer are ignored, because of how stack frames work ...

     Yes, that's well within the bounds of undefined behavior. The worst symptom of undefined behavior is having the program work exactly as you expect it to. It means that you have a bug that hasn't exhibited itself yet, and it will be difficult to track it down.

     You should not depend on that unless you have a very good reason to do so.

     If you change

     int (*fp)() = foo;-

     to

     int (*fp)(int) = foo;-

     the compiler will diagnose the incorrect call.

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   • What are the different between calling constructor and calling function pointer of constructor in C++

     Top Answer

     Answered Jan 28, 2024 · 0 votes

     Calling a constructor and calling a function pointer of a constructor in C++ are very similar in the sense that they are both quite impossible:

     • You cannot call a constructor in C++.
     • You cannot obtain a pointer to a constructor in C++.

     According to the C++ spec about constructors:

     Constructors have no names and cannot be called directly.

     So, in C++, you do not call constructors. The language does that for you when you use the new keyword, when you declare an object on the stack, etc. The expression new MyClass() might look like a constructor invocation, and it does in fact contain a constructor invocation, and so it might be mistaken for a constructor invocation, but that's not what it is; it is a "new expression", which includes, among other things, an invocation of a constructor. But the other things are crucial: you cannot just skip them and directly invoke the constructor.

     Function pointers of constructors do not exist because normally you cannot take the address of a constructor. If you examine the names exported by the DLL, and somehow figure out which name corresponds to the constructor, and use that name to obtain the entry point of that constructor from the DLL, you are cheating: you are doing something which is not normally supported by the language. As a result, you should not attempt to invoke that entry point. A constructor is only supposed to be invoked by the language.

     Also according to the C++ spec:

     A constructor is a special non-static member function of a class.

     (Emphasis mine.)

     A constructor assumes that memory has been allocated, and proceeds to initialize that memory. The language takes care of the memory allocation, but invoking the constructor directly does not. Since a constructor is non-static, it expects an uninitialized this to be passed to it, but you are not allocating any memory and you are not passing anything to the constructor. The result is exactly as expected: a crash.

     And besides, think about it: the constructor could not be internally allocating the memory, because how would it work then if the object was allocated on the stack? And how would it work if the constructor was being invoked by the constructor of a derived class which presumably occupies more memory?

     You can get your DLL to work by using a factory method. A factory method is a public static method which executes new ClassA() and returns the result, or declares ClassA() and returns it by value. Then, obtain the address of the factory method from the DLL, and invoke it.

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2. en.wikipedia.org › wiki › C_(programming_language)C (programming language) - Wikipedia

   en.wikipedia.org › wiki › C_(programming_language)

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   2 days ago · C Programming at Wikibooks. C ( pronounced / ˈsiː / – like the letter c) [6] is a general-purpose computer programming language. It was created in the 1970s by Dennis Ritchie, and remains very widely used and influential. By design, C's features cleanly reflect the capabilities of the targeted CPUs. It has found lasting use in operating ...

   • First appeared: 1972; 51 years ago
   • Stable release: C17, / June 2018; 5 years ago

   • Designed by: Dennis Ritchie

3. www.geeksforgeeks.org › stack-using-linked-list-in-cStack Using Linked List in C - GeeksforGeeks

   www.geeksforgeeks.org › stack-using-linked-list-in-c

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   3 days ago · The following is the algorithm for isEmpty function: Check if the top pointer of the stack is NULL. If NULL, return true, indicating the stack is empty. Otherwise return false indicating the stack is not empty. C Program to Implement a Stack Using Linked List. The below example demonstrates how to implement a stack using a linked list in C. C

4. People also ask

   What is a function in C?

   • In C, all executable code is contained within subroutines (also called "functions", though not in the sense of functional programming ). Function parameters are passed by value, although arrays are passed as pointers, i.e. the address of the first item in the array.

   C (programming language) - Wikipedia

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   What is C programming language used for?

   • C is commonly used on computer architectures that range from the largest supercomputers to the smallest microcontrollers and embedded systems . A successor to the programming language B, C was originally developed at Bell Labs by Ritchie between 1972 and 1973 to construct utilities running on Unix.

   C (programming language) - Wikipedia

   en.wikipedia.org/wiki/C_(programming_language)

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   What is a C library function?

   • Another common set of C library functions are those used by applications specifically targeted for Unix and Unix-like systems, especially functions which provide an interface to the kernel. These functions are detailed in various standards such as POSIX and the Single UNIX Specification .

   C (programming language) - Wikipedia

   en.wikipedia.org/wiki/C_(programming_language)

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   What are the functions of a programming language?

   • One of the most important functions of a programming language is to provide facilities for managing memory and the objects that are stored in memory. C provides three principal ways to allocate memory for objects:

   C (programming language) - Wikipedia

   en.wikipedia.org/wiki/C_(programming_language)

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5. www.geeksforgeeks.org › columnar-transposition-cipherColumnar Transposition Cipher - GeeksforGeeks

   www.geeksforgeeks.org › columnar-transposition-cipher

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   5 days ago · In a transposition cipher, the order of the alphabets is re-arranged to obtain the cipher-text. The message is written out in rows of a fixed length, and then read out again column by column, and the columns are chosen in some scrambled order. Width of the rows and the permutation of the columns are usually defined by a keyword.

6. www.geeksforgeeks.org › mirror-characters-stringMirror characters of a string - GeeksforGeeks

   www.geeksforgeeks.org › mirror-characters-string

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   5 days ago · Using Mapping: Follow the below steps: Firslty, mirror_characters () function takes a string and returns a number N. The first step is to map the characters to the mirrored characters using dictionary comprehension. The second step is to iterate over the characters in the string, starting from position N, and constructing the resulting string.

7. en.wikipedia.org › wiki › C++C++ - Wikipedia

   en.wikipedia.org › wiki › C++

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   1 day ago · 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).

   • Designed by: Bjarne Stroustrup
   • Stable release: C++20 (ISO/IEC 14882:2020), / 15 December 2020; 2 years ago

   • Developer: ISO/IEC JTC 1 (Joint Technical Committee 1) / SC 22 (Subcommittee 22) / WG 21 (Working Group 21)

8. pkg.go.dev › cmd › cgocgo command - cmd/cgo - Go Packages

   pkg.go.dev › cmd › cgo

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   4 days ago · To use cgo write normal Go code that imports a pseudo-package "C". The Go code can then refer to types such as C.size_t, variables such as C.stdout, or functions such as C.putchar. If the import of "C" is immediately preceded by a comment, that comment, called the preamble, is used as a header when compiling the C parts of the package.

9. en.wikipedia.org › wiki › Objective-CObjective-C - Wikipedia

   en.wikipedia.org › wiki › Objective-C

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   5 days ago · Objective-C. Objective-C is a high-level general-purpose, object-oriented programming language that adds Smalltalk -style messaging to the C [3] programming language. Originally developed by Brad Cox and Tom Love in the early 1980s, it was selected by NeXT for its NeXTSTEP operating system.