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In the Java programming language, the wildcard? is a special kind of type argument [1] that controls the type safety of the use of generic (parameterized) types. [2] It can be used in variable declarations and instantiations as well as in method definitions, but not in the definition of a generic type.
In Lisp, lists are the fundamental data type and can represent both program code and data. In most dialects, the list of the first three prime numbers could be written as (list 2 3 5) . In several dialects of Lisp, including Scheme , a list is a collection of pairs, consisting of a value and a pointer to the next pair (or null value), making a ...
Generic programming pioneer Alexander Stepanov wrote, Generic programming is about abstracting and classifying algorithms and data structures. It gets its inspiration from Knuth and not from type theory. Its goal is the incremental construction of systematic catalogs of useful, efficient and abstract algorithms and data structures.
The fundamental idea behind array programming is that operations apply at once to an entire set of values. This makes it a high-level programming model as it allows the programmer to think and operate on whole aggregates of data, without having to resort to explicit loops of individual scalar operations.
So ArrayList<String> is a subtype of List<String>, which is a subtype of Collection<String>. The subtyping relationship is preserved between the types automatically. When defining an interface, PayloadList, that associates an optional value of generic type P with each element, its declaration might look like:
Compared to non-generic code with manual casts, these casts will be the same, [74] but compared to compile-time verified code that would not need runtime casts and checks, these operations represent a performance overhead. C#/.NET generics guarantee type-safety and are verified at compile time, making extra checks/casts are unnecessary at runtime.
Generics are invariant, whereas arrays are covariant. [6] This is a benefit of using generic when compared to non-generic objects such as arrays. [6] Specifically, generics can help prevent run time exceptions by throwing a compile-time exception to force the developer to fix the code.
Inheritance, by contrast, typically targets the type rather than the instances, and is restricted to compile time. On the other hand, inheritance can be statically type-checked, while delegation generally cannot without generics (although a restricted version of delegation can be statically typesafe [7]). Delegation can be termed "run-time ...