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In JavaScript (see also JSON), all objects behave as associative arrays with string-valued keys, while the Map and WeakMap types take arbitrary objects as keys. In Lua, they are used as the primitive building block for all data structures. In Visual FoxPro, they are called Collections. The D language also supports associative arrays. [22]
The interface {} type can be used to model structured data of any arbitrary schema in Go, such as JSON or YAML data, by representing it as a map [string] interface {} (map of string to empty interface). This recursively describes data in the form of a dictionary with string keys and values of any type. [82]
The Properties object provides specific methods for saving and loading properties into files. Unlike a Table object, which cannot contain duplicate indexes, a Relation object is a collection in which elements can have the same index, which can be of any object type. A Stem object is created automatically when a compound variable is used.
Early ALGOL compilers supported a SWITCH data type which contains a list of "designational expressions". A GOTO statement could reference a switch variable and, by providing an index, branch to the desired destination. With experience it was realized that a more formal multi-way construct, with single point of entrance and exit, was needed.
Message passing is a key concept, if not the main concept, in object-oriented languages. Polymorphic functions parameterized by the class of some of their arguments are typically called methods . In languages with single dispatch , classes typically also include method definitions.
The $= type rule indicates that there is also a theory label, with the functor person, for a theory that defines the characteristic properties of the person type - implements the person interface - in terms of four given parameters of types string, day, Sex, and string.
In this example, the variable z will have the value 42. Although this may not be what the programmer anticipated, it is a well-defined result. If y were a different string, one that could not be converted to a number (e.g. "Hello World"), the result would be well-defined as well. Note that a program can be type-safe or memory-safe and still ...
/*Ruby has three member variable types: class, class instance, and instance. */ class Dog # The class variable is defined within the class body with two at-signs # and describes data about all Dogs *and* their derived Dog breeds (if any) @@sniffs = true end mutt = Dog. new mutt. class. sniffs #=> true class Poodle < Dog # The "class instance variable" is defined within the class body with a ...