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In functional programming, a result type is a monadic type holding a returned value or an error code. They provide an elegant way of handling errors, without resorting to exception handling; when a function that may fail returns a result type, the programmer is forced to consider success or failure paths, before getting access to the expected result; this eliminates the possibility of an erroneous programmer assumption.
typeResultev=Okv|Erre. [1] Either type is used for this purpose, which is defined by the standard library as dataEitherab=Lefta|Rightb, where a is the error type and b is the return type. [2] valueclassResult<outT>. [3] type('a,'b)result=Okof'a|Errorof'btype. [4] enumResult<T,E>{Ok(T),Err(E)}. [5] [6] Either type, [7] however Scala also has more conventional exception handling.@frozenenumResult<Success,Failure>whereFailure:Error. [8] std::expected<T,E>. [9] The result object has the methods is_ok() and is_err().
constCAT_FOUND: bool=true;fnmain(){letresult=pet_cat();ifresult.is_ok(){println!("Great, we could pet the cat!");}else{println!("Oh no, we couldn't pet the cat!");}}fnpet_cat()-> Result<(),String>{ifCAT_FOUND{Ok(())}else{Err(String::from("the cat is nowhere to be found"))}}Type inference, sometimes called type reconstruction, refers to the automatic detection of the type of an expression in a formal language. These include programming languages and mathematical type systems, but also natural languages in some branches of computer science and linguistics.
In computer programming, especially functional programming and type theory, an algebraic data type (ADT) is a kind of composite type, i.e., a type formed by combining other types.
In computer science, a tagged union, also called a variant, variant record, choice type, discriminated union, disjoint union, sum type or coproduct, is a data structure used to hold a value that could take on several different, but fixed, types. Only one of the types can be in use at any one time, and a tag field explicitly indicates which one is in use. It can be thought of as a type that has several "cases", each of which should be handled correctly when that type is manipulated. This is critical in defining recursive datatypes, in which some component of a value may have the same type as that value, for example in defining a type for representing trees, where it is necessary to distinguish multi-node subtrees and leaves. Like ordinary unions, tagged unions can save storage by overlapping storage areas for each type, since only one is in use at a time.
In computer programming, foreach loop is a control flow statement for traversing items in a collection. foreach is usually used in place of a standard for loop statement. Unlike other for loop constructs, however, foreach loops usually maintain no explicit counter: they essentially say "do this to everything in this set", rather than "do this x times". This avoids potential off-by-one errors and makes code simpler to read. In object-oriented languages, an iterator, even if implicit, is often used as the means of traversal.
Many programming language type systems support subtyping. For instance, if the type Cat is a subtype of Animal, then an expression of type Cat should be substitutable wherever an expression of type Animal is used.
typedef is a reserved keyword in the programming languages C, C++, and Objective-C. It is used to create an additional name (alias) for another data type, but does not create a new type, except in the obscure case of a qualified typedef of an array type where the typedef qualifiers are transferred to the array element type. As such, it is often used to simplify the syntax of declaring complex data structures consisting of struct and union types, although it is also commonly used to provide specific descriptive type names for integer data types of varying sizes.
Scala is a strong statically typed high-level general-purpose programming language that supports both object-oriented programming and functional programming. Designed to be concise, many of Scala's design decisions are intended to address criticisms of Java.
Programming languages are used for controlling the behavior of a machine. Like natural languages, programming languages follow rules for syntax and semantics.
Exception handling syntax is the set of keywords and/or structures provided by a computer programming language to allow exception handling, which separates the handling of errors that arise during a program's operation from its ordinary processes. Syntax for exception handling varies between programming languages, partly to cover semantic differences but largely to fit into each language's overall syntactic structure. Some languages do not call the relevant concept "exception handling"; others may not have direct facilities for it, but can still provide means to implement it.
C++11 is a version of the ISO/IEC 14882 standard for the C++ programming language. C++11 replaced the prior version of the C++ standard, called C++03, and was later replaced by C++14. The name follows the tradition of naming language versions by the publication year of the specification, though it was formerly named C++0x because it was expected to be published before 2010.
In computer programming, an anonymous function is a function definition that is not bound to an identifier. Anonymous functions are often arguments being passed to higher-order functions or used for constructing the result of a higher-order function that needs to return a function. If the function is only used once, or a limited number of times, an anonymous function may be syntactically lighter than using a named function. Anonymous functions are ubiquitous in functional programming languages and other languages with first-class functions, where they fulfil the same role for the function type as literals do for other data types.
In computing, a channel is a model for interprocess communication and synchronization via message passing. A message may be sent over a channel, and another process or thread is able to receive messages sent over a channel it has a reference to, as a stream. Different implementations of channels may be buffered or not, and either synchronous or asynchronous.
Type aliasing is a feature in some programming languages that allows the creation to refer to a type using another name. It does not create a new type hence does not increase type safety. It can be used to shorten a long name. Programing languages which allows type aliasing include C++, C# Crystal, D, Dart, Elixir, Elm, F#, Go, Hack, Haskell, Julia, Kotlin, Nim, OCaml, Python, Rust, Scala, Swift and TypeScript.
In programming languages and type theory, an option type or maybe type is a polymorphic type that represents encapsulation of an optional value; e.g., it is used as the return type of functions which may or may not return a meaningful value when they are applied. It consists of a constructor which either is empty, or which encapsulates the original data type A.
Different command-line argument parsing methods are used by different programming languages to parse command-line arguments.
Rust is a multi-paradigm, general-purpose programming language that emphasizes performance, type safety, and concurrency. It enforces memory safety—meaning that all references point to valid memory—without a garbage collector. To simultaneously enforce memory safety and prevent data races, its "borrow checker" tracks the object lifetime of all references in a program during compilation.
In computer programming, string interpolation is the process of evaluating a string literal containing one or more placeholders, yielding a result in which the placeholders are replaced with their corresponding values. It is a form of simple template processing or, in formal terms, a form of quasi-quotation. The placeholder may be a variable name, or in some languages an arbitrary expression, in either case evaluated in the current context.
The table shows a comparison of functional programming languages which compares various features and designs of different functional programming languages.
Kotlin is a cross-platform, statically typed, general-purpose high-level programming language with type inference. Kotlin is designed to interoperate fully with Java, and the JVM version of Kotlin's standard library depends on the Java Class Library, but type inference allows its syntax to be more concise. Kotlin mainly targets the JVM, but also compiles to JavaScript or native code via LLVM. Language development costs are borne by JetBrains, while the Kotlin Foundation protects the Kotlin trademark.
This article compares the syntax for defining and instantiating an algebraic data type (ADT), sometimes also referred to as a tagged union, in various programming languages.