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Folds can be regarded as consistently replacing the structural components of a data structure with functions and values. Lists, for example, are built up in many functional languages from two primitives: any list is either an empty list, commonly called nil ([]), or is constructed by prefixing an element in front of another list, creating what is called a cons node ( Cons(X1,Cons(X2,Cons ...
Rice's theorem establishes that this problem cannot be solved in general for all programs; however, it is possible to create a conservative (imprecise) analysis that will accept only programs that satisfy this constraint, while rejecting some correct programs, and definite assignment analysis is such an analysis. The Java [1] and C# [2 ...
The list of phone numbers would itself contain "PhoneNumber objects" and so on. Each such address-book entry is treated as a single object by the programming language (it can be referenced by a single variable containing a pointer to the object, for instance).
Data-flow analysis is a technique for gathering information about the possible set of values calculated at various points in a computer program.A program's control-flow graph (CFG) is used to determine those parts of a program to which a particular value assigned to a variable might propagate.
This means that it is no longer a problem to define Circle.stretchX, and the inheritance reflects the mathematical relationship between circles and ellipses. A disadvantage is that changing the value of an instance then requires an assignment, which is inconvenient and prone to programming errors, e.g., Orbit(planet[i]) := Orbit(planet[i]).stretchX
For example, think of A as Authors, and B as Books. An Author can write several Books, and a Book can be written by several Authors. In a relational database management system, such relationships are usually implemented by means of an associative table (also known as join table, junction table or cross-reference table), say, AB with two one-to-many relationships A → AB and B → AB.
Java 8 introduces default methods on interfaces. If A,B,C are interfaces, B,C can each provide a different implementation to an abstract method of A , causing the diamond problem. Either class D must reimplement the method (the body of which can simply forward the call to one of the super implementations), or the ambiguity will be rejected as a ...
In Java, is-a relation between the type parameters of one class or interface and the type parameters of another are determined by the extends and implements clauses. Using the Collections classes, ArrayList<E> implements List<E>, and List<E> extends Collection<E>. So ArrayList<String> is a subtype of List<String>, which is a subtype of ...