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Function Table
In computer science, a dispatch table is a table of pointers or memory addresses to functions or methods. Use of such a table is a common technique when implementing late binding in object-oriented programming. Perl implementation The following shows one way to implement a dispatch table in Perl, using a hash to store references to code (also known as function pointers). # Define the table using one anonymous code-ref and one named code-ref my %dispatch = ( "-h" => sub , "-g" => \&say_goodbye ); sub say_goodbye # Fetch the code ref from the table, and invoke it my $sub = $dispatch; print $sub ? $sub->() : "unknown argument\n"; Running this Perl program as perl greet -h will produce "hello", and running it as perl greet -g will produce "goodbye". JavaScript implementation Following is a demo of implementing dispatch table in JavaScript: var thingsWeCanDo = ; var doSomething = function(doWhat) Virtual method tables In object-oriented programming langua ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Computer Science
Computer science is the study of computation, automation, and information. Computer science spans theoretical disciplines (such as algorithms, theory of computation, information theory, and automation) to Applied science, practical disciplines (including the design and implementation of Computer architecture, hardware and Computer programming, software). Computer science is generally considered an area of research, academic research and distinct from computer programming. Algorithms and data structures are central to computer science. The theory of computation concerns abstract models of computation and general classes of computational problem, problems that can be solved using them. The fields of cryptography and computer security involve studying the means for secure communication and for preventing Vulnerability (computing), security vulnerabilities. Computer graphics (computer science), Computer graphics and computational geometry address the generation of images. Progr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Virtual Method
In object-oriented programming, in languages such as C++, and Object Pascal, a virtual function or virtual method is an inheritable and overridable function or method for which dynamic dispatch is facilitated. This concept is an important part of the (runtime) polymorphism portion of object-oriented programming (OOP). In short, a virtual function defines a target function to be executed, but the target might not be known at compile time. Most programming languages, such as JavaScript, PHP and Python, treat all methods as virtual by default and do not provide a modifier to change this behavior. However, some languages provide modifiers to prevent methods from being overridden by derived classes (such as the ''final'' keyword in Java and PHP). Purpose The concept of the virtual function solves the following problem: In object-oriented programming, when a derived class inherits from a base class, an object of the derived class may be referred to via a pointer or reference of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Code Reading
''Code Reading'' ({{ISBN, 0-201-79940-5) is a 2003 software development book written by Diomidis Spinellis. The book is directed to programmers who want to improve their code reading abilities. It discusses specific techniques for reading code written by others and outlines common programming concepts. The code examples used in the book are taken from real-life software and uses C to illustrate basic concepts. Excerpts from prominent open-source code systems like the Apache Web server, the hsqldb Java relational database engine, the NetBSD Unix distribution, the Perl language, the Tomcat application server, and the X Window System are presented. The book inaugurated Addison-Wesley's Effective Software Development Series, edited by Scott Meyers, and received the 2004 Software Development Productivity Award in the “Technical Books” category. It has been translated into Chinese, Greek, Japanese, Korean, Polish, and Russian. See also * Code review Code review (sometimes refer ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Diomidis Spinellis
Diomidis D. Spinellis ( el, Διομήδης Δ. Σπινέλλης; 2 February 1967, Athens) is a Greece, Greek computer science academic and author of the books ''Code Reading'', ''Code Quality'', ''Beautiful Architecture'' (co-author) and ''Effective Debugging''. Education Spinellis holds a Master of Engineering degree in Software Engineering and a Doctor of Philosophy, Ph.D. in Computer Science both from Imperial College London. His PhD was supervised by Susan Eisenbach and Sophia Drossopoulou. Career and research He is a professor at the Department of Management Science and Technology at the Athens University of Economics and Business, and a member of the ''IEEE Software'' editorial board, contributing the Tools of the Trade column. Since 2014, he is also editor-in-chief of ''IEEE Software''. Spinellis is a four-time winner of the International Obfuscated C Code Contest in 1988, 1990, 1991 and 1995. He is also a committer in the FreeBSD project, and author of a number of popu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Branch Table
In computer programming, a branch table or jump table is a method of transferring program control (Branch (computer science), branching) to another part of a program (or a different program that may have been dynamically loaded) using a table of branch or jump Instruction (computer science), instructions. It is a form of multiway branch. The branch table construction is commonly used when programming in assembly language but may also be generated by compilers, especially when implementing optimized switch statements whose values are densely packed together. Typical implementation A branch table consists of a serial list of unconditional branch instructions that is branched into using an Offset (computer science), offset created by multiple (mathematics), multiplying a sequential index by the instruction length (the number of bytes in memory occupied by each branch instruction). It relies on the fact that machine code Instruction (computer science), instructions for branching have a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Virtual Method Table
In computer programming, a virtual method table (VMT), virtual function table, virtual call table, dispatch table, vtable, or vftable is a mechanism used in a programming language to support dynamic dispatch (or run-time method binding). Whenever a class defines a virtual function (or method), most compilers add a hidden member variable to the class that points to an array of pointers to (virtual) functions called the virtual method table. These pointers are used at runtime to invoke the appropriate function implementations, because at compile time it may not yet be known if the base function is to be called or a derived one implemented by a class that inherits from the base class. There are many different ways to implement such dynamic dispatch, but use of virtual method tables is especially common among C++ and related languages (such as D and C#). Languages that separate the programmatic interface of objects from the implementation, like Visual Basic and Delphi, also te ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Class (computer Science)
In object-oriented programming, a class is an extensible program-code-template for creating objects, providing initial values for state (member variables) and implementations of behavior (member functions or methods). In many languages, the class name is used as the name for the class (the template itself), the name for the default constructor of the class (a subroutine that creates objects), and as the type of objects generated by instantiating the class; these distinct concepts are easily conflated. Although, to the point of conflation, one could argue that is a feature inherent in a language because of its polymorphic nature and why these languages are so powerful, dynamic and adaptable for use compared to languages without polymorphism present. Thus they can model dynamic systems (i.e. the real world, machine learning, AI) more easily. When an object is created by a constructor of the class, the resulting object is called an instance of the class, and the member variabl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Compiler
In computing, a compiler is a computer program that translates computer code written in one programming language (the ''source'' language) into another language (the ''target'' language). The name "compiler" is primarily used for programs that translate source code from a high-level programming language to a low-level programming language (e.g. assembly language, object code, or machine code) to create an executable program. Compilers: Principles, Techniques, and Tools by Alfred V. Aho, Ravi Sethi, Jeffrey D. Ullman - Second Edition, 2007 There are many different types of compilers which produce output in different useful forms. A ''cross-compiler'' produces code for a different CPU or operating system than the one on which the cross-compiler itself runs. A ''bootstrap compiler'' is often a temporary compiler, used for compiling a more permanent or better optimised compiler for a language. Related software include, a program that translates from a low-level language to a h ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Programming Language
A programming language is a system of notation for writing computer programs. Most programming languages are text-based formal languages, but they may also be graphical. They are a kind of computer language. The description of a programming language is usually split into the two components of syntax (form) and semantics (meaning), which are usually defined by a formal language. Some languages are defined by a specification document (for example, the C programming language is specified by an ISO Standard) while other languages (such as Perl) have a dominant implementation that is treated as a reference. Some languages have both, with the basic language defined by a standard and extensions taken from the dominant implementation being common. Programming language theory is the subfield of computer science that studies the design, implementation, analysis, characterization, and classification of programming languages. Definitions There are many considerations when defini ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pointer (computer Programming)
In computer science, a pointer is an object in many programming languages that stores a memory address. This can be that of another value located in computer memory, or in some cases, that of memory-mapped computer hardware. A pointer ''references'' a location in memory, and obtaining the value stored at that location is known as ''dereferencing'' the pointer. As an analogy, a page number in a book's index could be considered a pointer to the corresponding page; dereferencing such a pointer would be done by flipping to the page with the given page number and reading the text found on that page. The actual format and content of a pointer variable is dependent on the underlying computer architecture. Using pointers significantly improves performance for repetitive operations, like traversing iterable data structures (e.g. strings, lookup tables, control tables and tree structures). In particular, it is often much cheaper in time and space to copy and dereference pointers th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Function Pointer
A function pointer, also called a subroutine pointer or procedure pointer, is a pointer that points to a function. As opposed to referencing a data value, a function pointer points to executable code within memory. Dereferencing the function pointer yields the referenced function, which can be invoked and passed arguments just as in a normal function call. Such an invocation is also known as an "indirect" call, because the function is being invoked ''indirectly'' through a variable instead of ''directly'' through a fixed identifier or address. Function pointers can be used to simplify code by providing a simple way to select a function to execute based on run-time values. Function pointers are supported by third-generation programming languages (such as PL/I, COBOL, Fortran, dBASE dBL, and C) and object-oriented programming languages (such as C++, C#, and D). Simple function pointers The simplest implementation of a function (or subroutine) pointer is as a variable containi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Associative Array
In computer science, an associative array, map, symbol table, or dictionary is an abstract data type that stores a collection of (key, value) pairs, such that each possible key appears at most once in the collection. In mathematical terms an associative array is a function with ''finite'' domain. It supports 'lookup', 'remove', and 'insert' operations. The dictionary problem is the classic problem of designing efficient data structures that implement associative arrays. The two major solutions to the dictionary problem are hash tables and search trees..Dietzfelbinger, M., Karlin, A., Mehlhorn, K., Meyer auf der Heide, F., Rohnert, H., and Tarjan, R. E. 1994"Dynamic Perfect Hashing: Upper and Lower Bounds". SIAM J. Comput. 23, 4 (Aug. 1994), 738-761. http://portal.acm.org/citation.cfm?id=182370 In some cases it is also possible to solve the problem using directly addressed arrays, binary search trees, or other more specialized structures. Many programming languages include ass ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
