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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-code statement at runtime.
A closure-constructing operator creates a function object from a part of the program: the part of code given as an argument to the operator is part of the function, and so is the lexical environment: the bindings of the lexically visible variables are captured and stored in the function object, which is more commonly called a closure.
Two classes are created, A and B, the former is being a superclass of the latter, then one instance of each class is checked. The last expression gives true because A is a superclass of the class of b. Further, you can directly ask for the class of any object, and "compare" them (code below assumes having executed the code above):
According to this principle, member variables of a class are made private to hide and protect them from other code, and can only be modified by a public member function (the mutator method), which takes the desired new value as a parameter, optionally validates it, and modifies the private member variable.
In Ruby, all classes are open. In Python, classes can be created at runtime, and all can be modified afterward. [43] Objective-C categories permit the programmer to add methods to an existing class without the need to recompile that class or even have access to its source code.
In computer science, a programming language is said to have first-class functions if it treats functions as first-class citizens. This means the language supports passing functions as arguments to other functions, returning them as the values from other functions, and assigning them to variables or storing them in data structures. [ 1 ]
A procedural program is composed of one or more units or modules, either user coded or provided in a code library; each module is composed of one or more procedures, also called a function, routine, subroutine, or method, depending on the language. Examples of procedural languages include:
A traditional imperative program might use a loop to traverse and modify a list. A functional program, on the other hand, would probably use a higher-order "map" function that takes a function and a list, generating and returning a new list by applying the function to each list item.