text stringlengths 1 500 | source stringlengths 31 152 |
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e run-time environment) as a result of evaluating the main function, is an integer. The keyword void as a parameter list indicates that the main function takes no arguments.
The opening curly brace indicates the beginning of the code that defines the main function.
The next line of the program is a statement that calls... | https://en.wikipedia.org/wiki/C_(programming_language) |
tf function is passed (i.e. provided with) a single argument, which is the address of the first character in the string literal "hello, world\n". The string literal is an unnamed array set up automatically by the compiler, with elements of type char and a final NULL character (ASCII value 0) marking the end of the arra... | https://en.wikipedia.org/wiki/C_(programming_language) |
n is a standard escape sequence that C translates to a newline character, which, on output, signifies the end of the current line. The return value of the printf function is of type int, but it is silently discarded since it is not used. (A more careful program might test the return value to check that the printf funct... | https://en.wikipedia.org/wiki/C_(programming_language) |
ion. According to the C99 specification and newer, the main function (unlike any other function) will implicitly return a value of 0 upon reaching the } that terminates the function. The return value of 0 is interpreted by the run-time system as an exit code indicating successful execution of the function.
== Data ty... | https://en.wikipedia.org/wiki/C_(programming_language) |
scal. There are built-in types for integers of various sizes, both signed and unsigned, floating-point numbers, and enumerated types (enum). Integer type char is often used for single-byte characters. C99 added a Boolean data type. There are also derived types including arrays, pointers, records (struct), and union... | https://en.wikipedia.org/wiki/C_(programming_language) |
empts to ensure type correctness of most expressions, but the programmer can override the checks in various ways, either by using a type cast to explicitly convert a value from one type to another, or by using pointers or unions to reinterpret the underlying bits of a data object in some other way.
Some find C's declar... | https://en.wikipedia.org/wiki/C_(programming_language) |
eir use: "declaration reflects use".)
C's usual arithmetic conversions allow for efficient code to be generated, but can sometimes produce unexpected results. For example, a comparison of signed and unsigned integers of equal width requires a conversion of the signed value to unsigned. This can generate unexpected re... | https://en.wikipedia.org/wiki/C_(programming_language) |
ress or location of an object or function in memory. Pointers can be dereferenced to access data stored at the address pointed to, or to invoke a pointed-to function. Pointers can be manipulated using assignment or pointer arithmetic. The run-time representation of a pointer value is typically a raw memory address (... | https://en.wikipedia.org/wiki/C_(programming_language) |
ns including pointers can be type-checked at compile time. Pointer arithmetic is automatically scaled by the size of the pointed-to data type.
Pointers are used for many purposes in C. Text strings are commonly manipulated using pointers into arrays of characters. Dynamic memory allocation is performed using pointer... | https://en.wikipedia.org/wiki/C_(programming_language) |
implemented as dynamically allocated struct objects linked together using pointers. Pointers to other pointers are often used in multi-dimensional arrays and arrays of struct objects. Pointers to functions (function pointers) are useful for passing functions as arguments to higher-order functions (such as qsort or bs... | https://en.wikipedia.org/wiki/C_(programming_language) |
rencing a null pointer value is undefined, often resulting in a segmentation fault. Null pointer values are useful for indicating special cases such as no "next" pointer in the final node of a linked list, or as an error indication from functions returning pointers. In appropriate contexts in source code, such as for... | https://en.wikipedia.org/wiki/C_(programming_language) |
as the NULL macro defined by several standard headers or, since C23 with the constant nullptr. In conditional contexts, null pointer values evaluate to false, while all other pointer values evaluate to true.
Void pointers (void *) point to objects of unspecified type, and can therefore be used as "generic" data point... | https://en.wikipedia.org/wiki/C_(programming_language) |
c on them allowed, although they can easily be (and in many contexts implicitly are) converted to and from any other object pointer type.
Careless use of pointers is potentially dangerous. Because they are typically unchecked, a pointer variable can be made to point to any arbitrary location, which can cause undesirab... | https://en.wikipedia.org/wiki/C_(programming_language) |
nter arithmetic; the objects they point to may continue to be used after deallocation (dangling pointers); they may be used without having been initialized (wild pointers); or they may be directly assigned an unsafe value using a cast, union, or through another corrupt pointer. In general, C is permissive in allowing ... | https://en.wikipedia.org/wiki/C_(programming_language) |
Some other programming languages address these problems by using more restrictive reference types.
=== Arrays ===
Array types in C are traditionally of a fixed, static size specified at compile time. The more recent C99 standard also allows a form of variable-length arrays. However, it is also possible to allocate... | https://en.wikipedia.org/wiki/C_(programming_language) |
arrays are always accessed (in effect) via pointers, array accesses are typically not checked against the underlying array size, although some compilers may provide bounds checking as an option. Array bounds violations are therefore possible and can lead to various repercussions, including illegal memory accesses, cor... | https://en.wikipedia.org/wiki/C_(programming_language) |
ays, but rather relies on recursion within the type system to declare arrays of arrays, which effectively accomplishes the same thing. The index values of the resulting "multi-dimensional array" can be thought of as increasing in row-major order. Multi-dimensional arrays are commonly used in numerical algorithms (main... | https://en.wikipedia.org/wiki/C_(programming_language) |
n early versions of C the bounds of the array must be known fixed values or else explicitly passed to any subroutine that requires them, and dynamically sized arrays of arrays cannot be accessed using double indexing. (A workaround for this was to allocate the array with an additional "row vector" of pointers to the co... | https://en.wikipedia.org/wiki/C_(programming_language) |
s allocation of a two-dimensional array on the heap and the use of multi-dimensional array indexing for accesses (which can use bounds-checking on many C compilers):
And here is a similar implementation using C99's Auto VLA feature:
=== Array–pointer interchangeability ===
The subscript notation x[i] (where x design... | https://en.wikipedia.org/wiki/C_(programming_language) |
x + i points to is not the base address (pointed to by x) incremented by i bytes, but rather is defined to be the base address incremented by i multiplied by the size of an element that x points to. Thus, x[i] designates the i+1th element of the array.
Furthermore, in most expression contexts (a notable exception is a... | https://en.wikipedia.org/wiki/C_(programming_language) |
es that an array is never copied as a whole when named as an argument to a function, but rather only the address of its first element is passed. Therefore, although function calls in C use pass-by-value semantics, arrays are in effect passed by reference.
The total size of an array x can be determined by applying sizeo... | https://en.wikipedia.org/wiki/C_(programming_language) |
ment of an array A, as in n = sizeof A[0]. Thus, the number of elements in a declared array A can be determined as sizeof A / sizeof A[0]. Note, that if only a pointer to the first element is available as it is often the case in C code because of the automatic conversion described above, the information about the full ... | https://en.wikipedia.org/wiki/C_(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:
Static memory allocation: space for the object is provided in the binary at compile-time; these objects have an extent (or lifetime) as long as the binary which conta... | https://en.wikipedia.org/wiki/C_(programming_language) |
atically freed and reusable after the block in which they are declared is exited.
Dynamic memory allocation: blocks of memory of arbitrary size can be requested at run-time using library functions such as malloc from a region of memory called the heap; these blocks persist until subsequently freed for reuse by calling ... | https://en.wikipedia.org/wiki/C_(programming_language) |
For example, static memory allocation has little allocation overhead, automatic allocation may involve slightly more overhead, and dynamic memory allocation can potentially have a great deal of overhead for both allocation and deallocation. The persistent nature of static objects is useful for maintaining state informa... | https://en.wikipedia.org/wiki/C_(programming_language) |
either static memory or heap space, and dynamic memory allocation allows convenient allocation of objects whose size is known only at run-time. Most C programs make extensive use of all three.
Where possible, automatic or static allocation is usually simplest because the storage is managed by the compiler, freeing the ... | https://en.wikipedia.org/wiki/C_(programming_language) |
ange in size at runtime, and since static allocations (and automatic allocations before C99) must have a fixed size at compile-time, there are many situations in which dynamic allocation is necessary. Prior to the C99 standard, variable-sized arrays were a common example of this. (See the article on C dynamic memory a... | https://en.wikipedia.org/wiki/C_(programming_language) |
ed consequences, the dynamic allocation functions return an indication (in the form of a null pointer value) when the required storage cannot be allocated. (Static allocation that is too large is usually detected by the linker or loader, before the program can even begin execution.)
Unless otherwise specified, static ... | https://en.wikipedia.org/wiki/C_(programming_language) |
only if an initial value is explicitly specified; otherwise they initially have indeterminate values (typically, whatever bit pattern happens to be present in the storage, which might not even represent a valid value for that type). If the program attempts to access an uninitialized value, the results are undefined. Ma... | https://en.wikipedia.org/wiki/C_(programming_language) |
allocation has to be synchronized with its actual usage in any program to be reused as much as possible. For example, if the only pointer to a heap memory allocation goes out of scope or has its value overwritten before it is deallocated explicitly, then that memory cannot be recovered for later reuse and is essential... | https://en.wikipedia.org/wiki/C_(programming_language) |
subsequently, leading to unpredictable results. Typically, the failure symptoms appear in a portion of the program unrelated to the code that causes the error, making it difficult to diagnose the failure. Such issues are ameliorated in languages with automatic garbage collection.
== Libraries ==
The C programming lan... | https://en.wikipedia.org/wiki/C_(programming_language) |
file. Each library typically has a header file, which contains the prototypes of the functions contained within the library that may be used by a program, and declarations of special data types and macro symbols used with these functions. For a program to use a library, it must include the library's header file, and ... | https://en.wikipedia.org/wiki/C_(programming_language) |
library").
The most common C library is the C standard library, which is specified by the ISO and ANSI C standards and comes with every C implementation (implementations which target limited environments such as embedded systems may provide only a subset of the standard library). This library supports stream input and ... | https://en.wikipedia.org/wiki/C_(programming_language) |
.h) specify the interfaces for these and other standard library facilities.
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... | https://en.wikipedia.org/wiki/C_(programming_language) |
es available. Libraries are often written in C because C compilers generate efficient object code; programmers then create interfaces to the library so that the routines can be used from higher-level languages like Java, Perl, and Python.
=== File handling and streams ===
File input and output (I/O) is not part of th... | https://en.wikipedia.org/wiki/C_(programming_language) |
tdio.h). File handling is generally implemented through high-level I/O which works through streams. A stream is from this perspective a data flow that is independent of devices, while a file is a concrete device. The high-level I/O is done through the association of a stream to a file. In the C standard library, a buff... | https://en.wikipedia.org/wiki/C_(programming_language) |
ent waiting for slower devices, for example a hard drive or solid-state drive. Low-level I/O functions are not part of the standard C library but are generally part of "bare metal" programming (programming that is independent of any operating system such as most embedded programming). With few exceptions, implementatio... | https://en.wikipedia.org/wiki/C_(programming_language) |
nts with undefined behavior or possibly erroneous expressions, with greater rigor than that provided by the compiler.
Automated source code checking and auditing tools exist, such as Lint. A common practice is to use Lint to detect questionable code when a program is first written. Once a program passes Lint, it is the... | https://en.wikipedia.org/wiki/C_(programming_language) |
actually be errors. MISRA C is a proprietary set of guidelines to avoid such questionable code, developed for embedded systems.
There are also compilers, libraries, and operating system level mechanisms for performing actions that are not a standard part of C, such as bounds checking for arrays, detection of buffer ove... | https://en.wikipedia.org/wiki/C_(programming_language) |
algrind and linking with libraries containing special versions of the memory allocation functions can help uncover runtime errors in memory usage.
== Uses ==
=== Rationale for use in systems programming ===
C is widely used for systems programming in implementing operating systems and embedded system applications.... | https://en.wikipedia.org/wiki/C_(programming_language) |
so system-specific features (e.g. Control/Status Registers, I/O registers) can be configured and used with code written in C – it allows fullest control of the platform it is running on.
The code generated after compilation does not demand many system features, and can be invoked from some boot code in a straightforwar... | https://en.wikipedia.org/wiki/C_(programming_language) |
or the target processor, and consequently there is a low run-time demand on system resources – it is fast to execute.
With its rich set of operators, the C language can use many of the features of target CPUs. Where a particular CPU has more esoteric instructions, a language variant can be constructed with perhaps int... | https://en.wikipedia.org/wiki/C_(programming_language) |
to overlay structures onto blocks of binary data, allowing the data to be comprehended, navigated and modified – it can write data structures, even file systems.
The language supports a rich set of operators, including bit manipulation, for integer arithmetic and logic, and perhaps different sizes of floating point num... | https://en.wikipedia.org/wiki/C_(programming_language) |
and without too many features that generate extensive target code – it is comprehensible.
C has direct control over memory allocation and deallocation, which gives reasonable efficiency and predictable timing to memory-handling operations, without any concerns for sporadic stop-the-world garbage collection events – it ... | https://en.wikipedia.org/wiki/C_(programming_language) |
oc and free; a more sophisticated mechanism with arenas; or a version for an OS kernel that may suit DMA, use within interrupt handlers, or integrated with the virtual memory system.
Depending on the linker and environment, C code can also call libraries written in assembly language, and may be called from assembly lan... | https://en.wikipedia.org/wiki/C_(programming_language) |
n conjunction with other high-level languages, with calls both to C and from C supported – it interoperates well with other high-level code.
C has a very mature and broad ecosystem, including libraries, frameworks, open source compilers, debuggers and utilities, and is the de facto standard. It is likely the drivers al... | https://en.wikipedia.org/wiki/C_(programming_language) |
se another language.
=== Used for computationally-intensive libraries ===
C enables programmers to create efficient implementations of algorithms and data structures, because the layer of abstraction from hardware is thin, and its overhead is low, an important criterion for computationally intensive programs. For exa... | https://en.wikipedia.org/wiki/C_(programming_language) |
ly written in C. Many languages support calling library functions in C, for example, the Python-based framework NumPy uses C for the high-performance and hardware-interacting aspects.
=== Games ===
Computer games are often built from a combination of languages. C has featured significantly, especially for those game... | https://en.wikipedia.org/wiki/C_(programming_language) |
uage ===
C is sometimes used as an intermediate language by implementations of other languages. This approach may be used for portability or convenience; by using C as an intermediate language, additional machine-specific code generators are not necessary. C has some features, such as line-number preprocessor directiv... | https://en.wikipedia.org/wiki/C_(programming_language) |
's shortcomings have prompted the development of other C-based languages specifically designed for use as intermediate languages, such as C--. Also, contemporary major compilers GCC and LLVM both feature an intermediate representation that is not C, and those compilers support front ends for many languages including C.... | https://en.wikipedia.org/wiki/C_(programming_language) |
erpreters of other programming languages are often implemented in C. For example, the reference implementations of Python, Perl, Ruby, and PHP are written in C.
=== Once used for web development ===
Historically, C was sometimes used for web development using the Common Gateway Interface (CGI) as a "gateway" for info... | https://en.wikipedia.org/wiki/C_(programming_language) |
speed, stability, and near-universal availability. It is no longer common practice for web development to be done in C, and many other web development languages are popular. Applications where C-based web development continues include the HTTP configuration pages on routers, IoT devices and similar, although even he... | https://en.wikipedia.org/wiki/C_(programming_language) |
ar web servers, Apache HTTP Server and Nginx, are both written in C. These web servers interact with the operating system, listen on TCP ports for HTTP requests, and then serve up static web content, or cause the execution of other languages handling to 'render' content such as PHP, which is itself primarily written i... | https://en.wikipedia.org/wiki/C_(programming_language) |
cations ===
C has also been widely used to implement end-user applications. However, such applications can also be written in newer, higher-level languages.
== Limitations ==
the power of assembly language and the convenience of ... assembly language
While C has been popular, influential and hugely successful, it has... | https://en.wikipedia.org/wiki/C_(programming_language) |
leaks and dangling pointers.
The use of pointers and the direct manipulation of memory means corruption of memory is possible, perhaps due to programmer error, or insufficient checking of bad data.
There is some type checking, but it does not apply to areas like variadic functions, and the type checking can be triviall... | https://en.wikipedia.org/wiki/C_(programming_language) |
s a burden on the programmer to consider all possible outcomes, to protect against buffer overruns, array bounds checking, stack overflows, memory exhaustion, and consider race conditions, thread isolation, etc.
The use of pointers and the run-time manipulation of these means there may be two ways to access the same da... | https://en.wikipedia.org/wiki/C_(programming_language) |
ages are not possible in C. FORTRAN is considered faster.
Some of the standard library functions, e.g. scanf or strncat, can lead to buffer overruns.
There is limited standardisation in support for low-level variants in generated code, for example: different function calling conventions and ABI; different structure pa... | https://en.wikipedia.org/wiki/C_(programming_language) |
of these options may be handled with the preprocessor directive #pragma, and some with additional keywords e.g. use __cdecl calling convention. The directive and options are not consistently supported.
String handling using the standard library is code-intensive, with explicit memory management required.
The language ... | https://en.wikipedia.org/wiki/C_(programming_language) |
gainst inappropriate use of language features, which may lead to unmaintainable code. In particular, the C preprocessor can hide troubling effects such as double evaluation and worse. This facility for tricky code has been celebrated with competitions such as the International Obfuscated C Code Contest and the Underh... | https://en.wikipedia.org/wiki/C_(programming_language) |
ongjmp standard library functions have been used to implement a try-catch mechanism via macros.
For some purposes, restricted styles of C have been adopted, e.g. MISRA C or CERT C, in an attempt to reduce the opportunity for bugs. Databases such as CWE attempt to count the ways C etc. has vulnerabilities, along with r... | https://en.wikipedia.org/wiki/C_(programming_language) |
checks which may generate warnings to help identify many potential bugs.
== Related languages ==
C has both directly and indirectly influenced many later languages such as C++ and Java. The most pervasive influence has been syntactical; all of the languages mentioned combine the statement and (more or less recogniza... | https://en.wikipedia.org/wiki/C_(programming_language) |
s radically.
Several C or near-C interpreters exist, including Ch and CINT, which can also be used for scripting.
When object-oriented programming languages became popular, C++ and Objective-C were two different extensions of C that provided object-oriented capabilities. Both languages were originally implemented as so... | https://en.wikipedia.org/wiki/C_(programming_language) |
iginally named "C with Classes") was devised by Bjarne Stroustrup as an approach to providing object-oriented functionality with a C-like syntax. C++ adds greater typing strength, scoping, and other tools useful in object-oriented programming, and permits generic programming via templates. Nearly a superset of C, C++ n... | https://en.wikipedia.org/wiki/C_(programming_language) |
erset of C that permits object-oriented programming using a hybrid dynamic/static typing paradigm. Objective-C derives its syntax from both C and Smalltalk: syntax that involves preprocessing, expressions, function declarations, and function calls is inherited from C, while the syntax for object-oriented features was o... | https://en.wikipedia.org/wiki/C_(programming_language) |
== See also ==
Compatibility of C and C++
Comparison of Pascal and C
Comparison of programming languages
International Obfuscated C Code Contest
List of C-family programming languages
List of C compilers
== Notes ==
== References ==
== Sources ==
Ritchie, Dennis M. (March 1993). "The Development of the C Languag... | https://en.wikipedia.org/wiki/C_(programming_language) |
history". www.bell-labs.com. Retrieved March 29, 2022.
Ritchie, Dennis M. (1993). "The Development of the C Language". The Second ACM SIGPLAN Conference on History of Programming Languages (HOPL-II). ACM. pp. 201–208. doi:10.1145/154766.155580. ISBN 0-89791-570-4. Archived from the original on April 11, 2019. Retrieved... | https://en.wikipedia.org/wiki/C_(programming_language) |
110362-8.
== Further reading ==
Plauger, P.J. (1992). The Standard C Library (1 ed.). Prentice Hall. ISBN 978-0131315099. (source)
Banahan, M.; Brady, D.; Doran, M. (1991). The C Book: Featuring the ANSI C Standard (2 ed.). Addison-Wesley. ISBN 978-0201544336. (free)
Feuer, Alan R. (1985). The C Puzzle Book (1 ed.). ... | https://en.wikipedia.org/wiki/C_(programming_language) |
929. (archive)
King, K.N. (2008). C Programming: A Modern Approach (2 ed.). W. W. Norton. ISBN 978-0393979503. (archive)
Griffiths, David; Griffiths, Dawn (2012). Head First C (1 ed.). O'Reilly. ISBN 978-1449399917.
Perry, Greg; Miller, Dean (2013). C Programming: Absolute Beginner's Guide (3 ed.). Que. ISBN 978-078975... | https://en.wikipedia.org/wiki/C_(programming_language) |
(2 ed.). Manning. ISBN 978-1617295812. (free)
== External links ==
ISO C Working Group official website
ISO/IEC 9899, publicly available official C documents, including the C99 Rationale
"C99 with Technical corrigenda TC1, TC2, and TC3 included" (PDF). Archived (PDF) from the original on October 25, 2007. (3.61 MB)... | https://en.wikipedia.org/wiki/C_(programming_language) |
In computer programming, a programming idiom, code idiom or simply idiom is a code fragment having a semantic role which recurs frequently across software projects. It often expresses a special feature of a recurring construct in one or more programming languages, frameworks or libraries. This definition is rooted in t... | https://en.wikipedia.org/wiki/Programming_idiom |
rn in code, which is represented in implementation by contiguous or scattered code snippets. Generally speaking, a programming idiom's semantic role is a natural language expression of a simple task, algorithm, or data structure that is not a built-in feature in the programming language being used, or, conversely, the ... | https://en.wikipedia.org/wiki/Programming_idiom |
anguage and how to use them is an important part of gaining fluency in that language. It also helps to transfer knowledge in the form of analogies from one language or framework to another. Such idiomatic knowledge is widely used in crowdsourced repositories to help developers overcome programming barriers.
Mapping co... | https://en.wikipedia.org/wiki/Programming_idiom |
common patterns and idioms, developers can create mental models and schemata that help them quickly understand and navigate new code. Furthermore, by mapping these idioms to idiosyncrasies and specific use cases, developers can ensure that they are applying the correct approach and not overgeneralizing it.
One way to ... | https://en.wikipedia.org/wiki/Programming_idiom |
d to be adapted or modified to fit a particular project or development team. This can help ensure that developers are working with a shared understanding of best practices and can make informed decisions about when to use established idioms and when to adapt them to fit their specific needs.
A common misconception is t... | https://en.wikipedia.org/wiki/Programming_idiom |
iosyncrasy. An idiom implies the semantics of some code in a programming language has similarities to other languages or frameworks. For example, an idiosyncratic way to manage dynamic memory in C would be to use the C standard library functions malloc and free, whereas idiomatic refers to manual memory management as r... | https://en.wikipedia.org/wiki/Programming_idiom |
both cases, the semantics of the code are intelligible to developers familiar with C or C++, once the idiomatic or idiosyncratic rationale is exposed to them. However, while idiomatic rationale is often general to the programming domain, idiosyncratic rationale is frequently tied to specific API terminology.
== Exam... | https://en.wikipedia.org/wiki/Programming_idiom |
s between a known language and a new one.
It has several implementations, among them the code fragments for C++:
For Java:
=== Inserting an element in an array ===
This idiom helps developers understand how to manipulate collections in a given language, particularly inserting an element x at a position i in a list s... | https://en.wikipedia.org/wiki/Programming_idiom |
on
Embedded SQL
Idiom
== References ==
== External links ==
programming-idioms.org shows short idioms implementations in most mainstream languages.
C++ programming idioms from Wikibooks. | https://en.wikipedia.org/wiki/Programming_idiom |
In computer science, reflective programming or reflection is the ability of a process to examine, introspect, and modify its own structure and behavior.
== Historical background ==
The earliest computers were programmed in their native assembly languages, which were inherently reflective, as these original architectu... | https://en.wikipedia.org/wiki/Reflective_programming |
-level compiled languages such as ALGOL, COBOL, Fortran, Pascal, and C, this reflective ability largely disappeared until new programming languages with reflection built into their type systems appeared.
Brian Cantwell Smith's 1982 doctoral dissertation introduced the notion of computational reflection in procedural pr... | https://en.wikipedia.org/wiki/Reflective_programming |
mmers make generic software libraries to display data, process different formats of data, perform serialization and deserialization of data for communication, or do bundling and unbundling of data for containers or bursts of communication.
Effective use of reflection almost always requires a plan: A design framework, e... | https://en.wikipedia.org/wiki/Reflective_programming |
riented code. For example, it assists languages such as Java to operate well in networks by enabling libraries for serialization, bundling and varying data formats. Languages without reflection such as C are required to use auxiliary compilers for tasks like Abstract Syntax Notation to produce code for serialization an... | https://en.wikipedia.org/wiki/Reflective_programming |
nt can monitor the execution of an enclosure of code and can modify itself according to a desired goal of that enclosure. This is typically accomplished by dynamically assigning program code at runtime.
In object-oriented programming languages such as Java, reflection allows inspection of classes, interfaces, fields an... | https://en.wikipedia.org/wiki/Reflective_programming |
new objects and invocation of methods.
Reflection is often used as part of software testing, such as for the runtime creation/instantiation of mock objects.
Reflection is also a key strategy for metaprogramming.
In some object-oriented programming languages such as C# and Java, reflection can be used to bypass member ... | https://en.wikipedia.org/wiki/Reflective_programming |
n-public property. It is also possible to find non-public methods of classes and types and manually invoke them. This works for project-internal files as well as external libraries such as .NET's assemblies and Java's archives.
== Implementation ==
A language that supports reflection provides a number of features av... | https://en.wikipedia.org/wiki/Reflective_programming |
ties to:
Discover and modify source-code constructions (such as code blocks, classes, methods, protocols, etc.) as first-class objects at runtime.
Convert a string matching the symbolic name of a class or function into a reference to or invocation of that class or function.
Evaluate a string as if it were a source-cod... | https://en.wikipedia.org/wiki/Reflective_programming |
nstruct.
These features can be implemented in different ways. In MOO, reflection forms a natural part of everyday programming idiom. When verbs (methods) are called, various variables such as verb (the name of the verb being called) and this (the object on which the verb is called) are populated to give the context of ... | https://en.wikipedia.org/wiki/Reflective_programming |
y which the current verb was eventually called, performing tests on callers()[0] (the command invoked by the original user) allows the verb to protect itself against unauthorised use.
Compiled languages rely on their runtime system to provide information about the source code. A compiled Objective-C executable, for exa... | https://en.wikipedia.org/wiki/Reflective_programming |
hods (or selectors for these methods) compiled into the program. In a compiled language that supports runtime creation of functions, such as Common Lisp, the runtime environment must include a compiler or an interpreter.
Reflection can be implemented for languages without built-in reflection by using a program transfor... | https://en.wikipedia.org/wiki/Reflective_programming |
ected control flow paths through an application, potentially bypassing security measures. This may be exploited by attackers. Historical vulnerabilities in Java caused by unsafe reflection allowed code retrieved from potentially untrusted remote machines to break out of the Java sandbox security mechanism. A large scal... | https://en.wikipedia.org/wiki/Reflective_programming |
the most exploited.
== Examples ==
The following code snippets create an instance foo of class Foo and invoke its method PrintHello. For each programming language, normal and reflection-based call sequences are shown.
=== Common Lisp ===
The following is an example in Common Lisp using the Common Lisp Object System... | https://en.wikipedia.org/wiki/Reflective_programming |
at a TFoo class has been declared in a unit called Unit1:
=== eC ===
The following is an example in eC:
=== Go ===
The following is an example in Go:
=== Java ===
The following is an example in Java:
=== JavaScript ===
The following is an example in JavaScript:
=== Julia ===
The following is an example in Jul... | https://en.wikipedia.org/wiki/Reflective_programming |
used:
=== Perl ===
The following is an example in Perl:
=== PHP ===
The following is an example in PHP:
=== Python ===
The following is an example in Python:
=== R ===
The following is an example in R:
=== Ruby ===
The following is an example in Ruby:
=== Xojo ===
The following is an example using Xojo:
=... | https://en.wikipedia.org/wiki/Reflective_programming |
ilers)
Self-modifying code
Type introspection
typeof
== References ==
=== Citations ===
=== Sources ===
== Further reading ==
Ira R. Forman and Nate Forman, Java Reflection in Action (2005), ISBN 1-932394-18-4
Ira R. Forman and Scott Danforth, Putting Metaclasses to Work (1999), ISBN 0-201-43305-2
== External... | https://en.wikipedia.org/wiki/Reflective_programming |
-Oriented Programming
Brian Foote's pages on Reflection in Smalltalk
Java Reflection API Tutorial from Oracle | https://en.wikipedia.org/wiki/Reflective_programming |
In computer science, extensible programming is a style of computer programming that focuses on mechanisms to extend the programming language, compiler, and runtime system (environment). Extensible programming languages, supporting this style of programming, were an active area of work in the 1960s, but the movement was... | https://en.wikipedia.org/wiki/Extensible_programming |
ement ==
The first paper usually associated with the extensible programming language movement is M. Douglas McIlroy's 1960 paper on macros for high-level programming languages. Another early description of the principle of extensibility occurs in Brooker and Morris's 1960 paper on the compiler-compiler. The peak of the... | https://en.wikipedia.org/wiki/Extensible_programming |
as essentially a post mortem. The Forth was an exception, but it went essentially unnoticed.
=== Character of the historical movement ===
As typically envisioned, an extensible language consisted of a base language providing elementary computing facilities, and a metalanguage able to modify the base language. A progr... | https://en.wikipedia.org/wiki/Extensible_programming |
nique used in the movement was macro definition. Grammar modification was also closely associated with the movement, resulting in the eventual development of adaptive grammar formalisms. The Lisp language community remained separate from the extensible language community, apparently because, as one researcher observed,... | https://en.wikipedia.org/wiki/Extensible_programming |
age. ... this can be seen very easily from the fact that Lisp has been used as an extendible language for years.
At the 1969 conference, Simula was presented as an extensible language.
Standish described three classes of language extension, which he named paraphrase, orthophrase, and metaphrase (otherwise paraphrase an... | https://en.wikipedia.org/wiki/Extensible_programming |
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