Generic programming: Difference between revisions

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====Genericity in .NET [C#, VB.NET]====

Generics were added as part of [[.NET Framework#.NET Framework 2.0|.NET Framework 2.0]] in November 2005, based on a research prototype from Microsoft Research started in 1999.<ref>[https://docs.microsoft.com/en-us/archive/blogs/dsyme/netc-generics-history-some-photos-from-feb-1999 .NET/C# Generics History: Some Photos From Feb 1999]</ref> Although similar to generics in Java, .NET generics do not apply [[type erasure]],{{sfn|Albahari|2022}}{{rp|208-209}}, but implement generics as a first class mechanism in the runtime using [[Reification (computer science)|reification]]. This design choice provides additional functionality, such as allowing [[Reflection (computer science)|reflection]] with preservation of generic types, as well as alleviating some of the limitations of erasure (such as being unable to create generic arrays).<ref>[https://www.ondotnet.com/pub/a/dotnet/2005/10/17/interview-with-anders-hejlsberg.html C#: Yesterday, Today, and Tomorrow: An Interview with Anders Hejlsberg]</ref><ref>[https://www.artima.com/intv/generics2.html Generics in C#, Java, and C++]</ref> This also means that there is no performance hit from runtime [[Type conversion|casts]] and normally expensive [[Boxing (computer science)|boxing conversions]]. When primitive and value types are used as generic arguments, they get specialized implementations, allowing for efficient generic [[Collection class|collections]] and methods. As in C++ and Java, nested generic types such as Dictionary<string, List<int>> are valid types, however are advised against for member signatures in code analysis design rules.<ref>[https://msdn.microsoft.com/en-us/library/ms182144.aspx Code Analysis CA1006: Do not nest generic types in member signatures]</ref>

.NET allows six varieties of generic type constraints using the <code>where</code> keyword including restricting generic types to be value types, to be classes, to have constructors, and to implement interfaces.<ref>[https://msdn2.microsoft.com/en-us/library/d5x73970.aspx Constraints on Type Parameters (C# Programming Guide)]</ref> Below is an example with an interface constraint:

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===Other languages===

Languages in the [[ML (programming language)|ML]] family support generic programming through [[Parametric polymorphism |parametric polymorphism]] and generic [[Modular programming|modules]] called ''functors.'' Both [[Standard ML]] and [[OCaml]] provide functors, which are similar to class templates and to Ada's generic packages. [[Scheme (programming language)|Scheme]] syntactic abstractions also have a connection to genericity – these are in fact a superset of C++ templates.

A [[Verilog]] module may take one or more parameters, to which their actual values are assigned upon the instantiation of the module. One example is a generic [[Hardware register|register]] array where the array width is given via a parameter. Such an array, combined with a generic wire vector, can make a generic buffer or memory module with an arbitrary bit width out of a single module implementation.<ref>Verilog by Example, Section ''The Rest for Reference''. Blaine C. Readler, Full Arc Press, 2011. {{ISBN|978-0-9834973-0-1}}</ref>