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In computer science, type conversion or typecasting refers to changing an entity of one data type into another. This is done to take advantage of certain features of type hierarchies. For instance, values from a more limited set, such as integers, can be stored in a more compact format and later converted to a different format enabling operations not previously possible, such as division with several decimal places' worth of accuracy. In object-oriented programming languages, type conversion allows programs to treat objects of one type as one of their ancestor types to simplify interacting with them. Computer science, or computing science, is the study of the theoretical foundations of information and computation and their implementation and application in computer systems. ...
In programming languages a data type defines a set of values and the allowable operations on those values[1]. For example, in the Java programming language, the int type represents the set of 32-bit integers ranging in value from -2,147,483,648 to 2,147,483,647, and...
Object-oriented programming (OOP) is a computer programming paradigm in which a software system is modeled as a set of objects that interact with each other. ...
There are two types of conversion: implicit and explicit. The term for implicit type conversion is coercion. The most common form of explicit type conversion is known as casting. Explicit type conversion can also be achieved with separately defined conversion routines such as an overloaded object constructor. In computer science, polymorphism means allowing a single definition to be used with different types of data (specifically, different classes of objects). ...
In strictly mathematical branches of computer science the term object is used in a purely mathematical sense to refer to any thing. While this interpretation is useful in the discussion of abstract theory, it is not concrete enough to serve as a primitive datatype in the discussion of more concrete...
In object-oriented programming, a constructor (sometimes shortened to ctor) in a class is a special block of statements called when an object is created, either when it is declared (statically constructed on the stack, possible in C++ but not in Java and other object-oriented languages) or dynamically constructed...
Implicit type conversion Implicit type conversion, also known as coercion, is an automatic type conversion by the compiler. Some languages allow, or even require, compilers to provide coercion. A diagram of the operation of a typical multi-language, multi-target compiler. ...
In a mixed-type expression, data of one or more subtypes can be converted to a supertype as needed at runtime so that the program will run correctly. For example, the following is legal C language code: In computer science, a subtype states that if given type A is compatible with type B, then A is a subtype of B while not always vice versa. ...
In computer science, a subtype is a datatype that is generally related to another datatype (the supertype) by some notion of substitutability, meaning that computer programs written to operate on elements of the supertype can also operate on elements of the subtype. ...
In computer science, runtime or run time describes the operation of a computer program, the duration of its execution, from beginning to termination (compare compile time). ...
C is a general-purpose, block structured, procedural, imperative computer programming language developed in 1972 by Dennis Ritchie at the Bell Telephone Laboratories for use with the Unix operating system. ...
double d; long l; int i; if (d > i) d = i; if (i > l) l = i; if (d == l) d *= 2; Although d, l and i belong to different data types, they will be automatically converted to equal data types each time a comparison or assignment is executed. This behavior should be used with caution, as unintended consequences can arise. Data can be lost when floating-point representations are converted to integral representations as the fractional components of the floating-point values will be truncated (rounded down). Conversely, converting from an integral representation to a floating-point one can also lose precision, since the floating-point type may be unable to represent the integer exactly (for example, float might be an IEEE 754 single precision type, which cannot represent the integer 16777217 exactly, while a 32-bit integer type can). This can lead to situations such as storing the same integer value into two variables of type int and type single which return false if compared for equality. The IEEE Standard for Binary Floating-Point Arithmetic (IEEE 754) is the most widely-used standard for floating-point computation, and is followed by many CPU and FPU implementations. ...
Explicit type conversion There are several kinds of explicit conversion. - checked
- Before the conversion is performed, a runtime check is done to see if the destination type can hold the source value. If not, an error condition is raised.
- unchecked
- No check is performed. If the destination type cannot hold the source value, the result is undefined.
- bit pattern
- The data is not interpreted at all, and its raw bit representation is copied verbatim. This can also be achieved via aliasing.
Each programming language has its own rules on how types can be converted. In general, both objects and fundamental data types can be converted. In computing, aliasing is a term that generally means that one variable or some reference, when changed, has an indirect (usually unexpected) effect on some other data. ...
A programming language is an artificial language that can be used to control the behavior of a machine, particularly a computer. ...
Static cast In C++ the static_cast operator changes expressions of one static type to objects and values of another static type. C++ (pronounced see plus plus, IPA: ) is a general-purpose programming language with high-level and low-level capabilities. ...
static_cast<type> (object); The type parameter must be a data type for which there is a known method for converting object to, whether this be a builtin or through a casting function. It can be a reference or an enumerator.
The static_cast operator can be used for operations such as
- Converting a pointer to a base class to a pointer to a derived class,
- Convert numeric data types such as enums to ints or ints to floats.
However, static_cast conversions are not necessarily safe as no run-time type check is done which can cause casting between incompatible data types, for example pointers. However, this is checked at compile time to prevent casting obviously incompatibles. Also, sometimes static_cast between pointer to base to pointer to derived will produce an erroneous result, because of the object layout model.
See also Wikibooks' Transwiki has more about this subject: Type conversion Image File history File links Wikibooks-logo-en. ...
In computer science, type punning is a common term for any programming technique that subverts or circumvents the type system of a programming language in order to achieve an effect that would be difficult or impossible to achieve within the bounds of the formal language. ...
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