Ceylon (programming language)

Last updated

Ceylon
Ceylon (programming language) logo.png
Paradigm Object-oriented
Designed by Gavin King
Developer Eclipse Foundation
First appeared2011;13 years ago (2011)
Stable release
1.3.3 / August 21, 2017;6 years ago (2017-08-21)
Typing discipline Static, strong, safe
Platform Java virtual machine, JavaScript
License Apache License 2.0
Filename extensions .ceylon [1]
Website ceylon-lang.org
Influenced by
Java, [2] Scala, Smalltalk, ML, [3] Lisp, [4] Whiley [5]

Ceylon was an object-oriented, strongly statically typed programming language with an emphasis on immutability, created by Red Hat. Ceylon programs run on the Java virtual machine (JVM), and could be compiled to JavaScript. [6] [7] The language design focuses on source code readability, predictability, toolability, modularity, and metaprogrammability. [8]

Contents

Important features of Ceylon include: [9]

The name "Ceylon" is an oblique reference to Java, in that Java and Sri Lanka, formerly known as Ceylon, are islands known for growth and export of coffee and tea.

In August 2017, Ceylon was donated to the Eclipse Foundation. Development slowed down and finally stopped in 2020. [13] In April 2023, Eclipse Foundation declared the termination of the transition. [14]

Language features

Ceylon is heavily influenced by Java's syntax, but adds many new features.

Type system

One of the most novel aspects of Ceylon compared to Java is its type system. Ceylon foregoes Java's primitive types [15] and boxing in favor of a type system composed entirely of first-class objects. While this may cause boxing overhead in some situations, it makes the type system more uniform.

Ceylon allows for union and intersection types, in a similar fashion to TypeScript, Whiley and Flow.

Union types, written A|B, allow a variable to have more than one type. The following example shows a Ceylon function which may take either an integer or a string:

sharedvoidintegerOrString(Integer|Stringinput){if(isIntegerinput){print("Got the integer ``input``");}else{print("Got the string '``input``'");}}

Intersection types, written A&B, are the theoretical foundation of flow-sensitive typing:

sharedvoidintegerOrString(Integer|Stringinput){Integeradded=input+6;// illegal; the + operator is not defined on Integer|Stringif(isIntegerinput){Integeradded=input+6;// legal; input is now known to be an Integerprint("Got the integer ``input``");}else{print("Got the string '``input``'");}}

The condition is Integer input narrows the type of input to <Integer|String>& Integer, which distributes to Integer&Integer | String&Integer, which, as String and Integer are disjoint types, is equivalent to Integer&Integer | Nothing (Nothing is the empty bottom type), which simplifies to just Integer.

Null safety

Union and intersection types are used to provide null safety. The top type of the Ceylon type hierarchy is the class Anything, which has two subclasses: Object, the superclass of all normal classes and all interfaces, and Null, with the only instance null. Since Object and Null are disjoint types, most regular types like Integer or List<String> are not nullable; a nullable type is the union Integer|Null, abbreviated Integer?. [16]

Intersection types can be used to get a non-optional type out of a possibly-optional type, such as a type parameter. For example, the signature of a function that removes null elements from a stream of values could be:

Iterable<Element&Object>removeNulls<Element>(Iterable<Element>stream);

When removeNulls is called with a stream of Integer|Null elements, the result will be a stream of <Integer|Null> & Object elements, which simplifies to Integer.

Functions

Similarly to many modern languages, Ceylon supports first class functions and higher order functions, including function types and anonymous functions [17] 

// A top-level higher-order function using block syntax (not associated with any user-created classes)Stringprocess(Stringtext,StringtransformString(StringtoChange)){returntransformString(text);}// A top-level function calling String.reverse in expression form.Stringreverse(Stringtext)=>text.reversed;// A function reference to String.reversed but mostly equivalent to the function above.String(String)reverseFunctionReference=String.reversed;// An example where the top-level function above is provided as an argument to the higher-order function aboveStringreversed1=process("one",reverse);// An example where an anonymous function - (text) => text+text - is provided to the higher-order function above. Stringreversed2=process("one",(text)=>text+text);

Enumerated types

Similar to Java and many other languages, and with a similar mechanism as algebraic types, Ceylon supports enumerated types, otherwise known as enums. This is implemented in Ceylon with a pattern of limiting the instances of an abstract class at declaration to a limited set of objects (in this case, singleton instances). Another way to implement this pattern is with the new constructor feature in Ceylon 1.2 where the objects are implemented as different named constructor declarations. [18] 

// Traditional syntax for enumerated type, in this case, limiting the instances to three objects(for this purpose: Singletons)abstractclassVehicle(sharedStringname)ofplane|train|automobile{}objectplaneextendsVehicle("plane"){}objecttrainextendsVehicle("train"){}objectautomobileextendsVehicle("automobile"){}// Compile error: type is not a subtype of any case of enumerated supertype: 'boat' inherits 'Vehicle'//object boat extends Vehicle("boat") {}// New (as of Ceylon 1.2.0) constructor-based syntaxclassVehicleofplane|train|automobile{Stringname;abstractnewnamed(StringpName){name=pName;}sharednewplaneextendsnamed("plane"){}sharednewtrainextendsnamed("train"){}sharednewautomobileextendsnamed("automobile"){}// Compile error: value constructor does not occur in of clause of non-abstract enumerated class: 'boat' is not listed in the of clause of 'Vehicle'//shared new boat extends named("boat") {}}

Type inference

Ceylon is strongly and statically typed, but also has support for type inference. The value keyword is used to infer the type of a variable, and the function keyword is used to infer the type of a function. The following two definition pairs are each equivalent:

Integeri=3;valuei=3;Integeradd(Integeri1,Integeri2){returni1+i2;}functionadd(Integeri1,Integeri2){returni1+i2;}

However, to make single-pass type inference possible, type inference is only allowed for non-toplevel and unshared declarations. [19]

Entry point with names

By default the starter (ceylon run) runs the shared run() function of a module:

/* The classic Hello World program */sharedvoidrun(){print("Hello, World!");}

but any other shared function without parameters can be used as main calling the program with the run parameter, like this:

ceylon run --compile=force --run hello default

Versions

Versions of Ceylon released: [20]

License

All parts of Ceylon are available as free software, mostly the Apache License. [21] Part of the source code is licensed under LGPL.

See also

Related Research Articles

<span class="mw-page-title-main">PHP</span> Scripting language created in 1994

PHP is a general-purpose scripting language geared towards web development. It was originally created by Danish-Canadian programmer Rasmus Lerdorf in 1993 and released in 1995. The PHP reference implementation is now produced by the PHP Group. PHP was originally an abbreviation of Personal Home Page, but it now stands for the recursive initialism PHP: Hypertext Preprocessor.

In computer programming, a parameter or a formal argument is a special kind of variable used in a subroutine to refer to one of the pieces of data provided as input to the subroutine. These pieces of data are the values of the arguments with which the subroutine is going to be called/invoked. An ordered list of parameters is usually included in the definition of a subroutine, so that, each time the subroutine is called, its arguments for that call are evaluated, and the resulting values can be assigned to the corresponding parameters.

<span class="mw-page-title-main">Apache Groovy</span> Programming language

Apache Groovy is a Java-syntax-compatible object-oriented programming language for the Java platform. It is both a static and dynamic language with features similar to those of Python, Ruby, and Smalltalk. It can be used as both a programming language and a scripting language for the Java Platform, is compiled to Java virtual machine (JVM) bytecode, and interoperates seamlessly with other Java code and libraries. Groovy uses a curly-bracket syntax similar to Java's. Groovy supports closures, multiline strings, and expressions embedded in strings. Much of Groovy's power lies in its AST transformations, triggered through annotations.

<span class="mw-page-title-main">ActionScript</span> Object-oriented programming language created for the Flash multimedia platform

ActionScript is an object-oriented programming language originally developed by Macromedia Inc.. It is influenced by HyperTalk, the scripting language for HyperCard. It is now an implementation of ECMAScript, though it originally arose as a sibling, both being influenced by HyperTalk. ActionScript code is usually converted to byte-code format by a compiler.

This article compares two programming languages: C# with Java. While the focus of this article is mainly the languages and their features, such a comparison will necessarily also consider some features of platforms and libraries. For a more detailed comparison of the platforms, see Comparison of the Java and .NET platforms.

<span class="mw-page-title-main">Java syntax</span> Set of rules defining correctly structured program

The syntax of Java is the set of rules defining how a Java program is written and interpreted.

In computer science, the Boolean is a data type that has one of two possible values which is intended to represent the two truth values of logic and Boolean algebra. It is named after George Boole, who first defined an algebraic system of logic in the mid 19th century. The Boolean data type is primarily associated with conditional statements, which allow different actions by changing control flow depending on whether a programmer-specified Boolean condition evaluates to true or false. It is a special case of a more general logical data type—logic does not always need to be Boolean.

<span class="mw-page-title-main">XMLHttpRequest</span> Web API to transfer data between a web browser and a web server

XMLHttpRequest (XHR) is a JavaScript class containing methods to asynchronously transmit HTTP requests from a web browser to a web server. The methods allow a browser-based application to make a fine-grained server call and store the results in XMLHttpRequest's responseText attribute. The XMLHttpRequest class is a component of Ajax programming. Prior to Ajax, an HTML form needed to be completely sent to the server followed by a complete browser page refresh.

The computer programming languages C and Pascal have similar times of origin, influences, and purposes. Both were used to design their own compilers early in their lifetimes. The original Pascal definition appeared in 1969 and a first compiler in 1970. The first version of C appeared in 1972.

In computer programming, an enumerated type is a data type consisting of a set of named values called elements, members, enumeral, or enumerators of the type. The enumerator names are usually identifiers that behave as constants in the language. An enumerated type can be seen as a degenerate tagged union of unit type. A variable that has been declared as having an enumerated type can be assigned any of the enumerators as a value. In other words, an enumerated type has values that are different from each other, and that can be compared and assigned, but are not specified by the programmer as having any particular concrete representation in the computer's memory; compilers and interpreters can represent them arbitrarily.

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.

Generics are a facility of generic programming that were added to the Java programming language in 2004 within version J2SE 5.0. They were designed to extend Java's type system to allow "a type or method to operate on objects of various types while providing compile-time type safety". The aspect compile-time type safety was not fully achieved, since it was shown in 2016 that it is not guaranteed in all cases.

In computer science, a three-way comparison takes two values A and B belonging to a type with a total order and determines whether A < B, A = B, or A > B in a single operation, in accordance with the mathematical law of trichotomy.

This article describes the syntax of the C# programming language. The features described are compatible with .NET Framework and Mono.

NekoVM is a virtual machine developed by Nicolas Cannasse as part of research and development (R&D) efforts at two independent video game developers in Bordeaux, France: first at Motion Twin and then at Shiro Games. NekoVM's native language is the bytecode for a high-level dynamically typed programming language called Neko. This pairing allows Neko to be used directly as an embedded scripting language, or to target NekoVM by compiling another language to NekoVM bytecode.

In software engineering, the module pattern is a design pattern used to implement the concept of software modules, defined by modular programming, in a programming language with incomplete direct support for the concept.

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.

Swift is a high-level general-purpose, multi-paradigm, compiled programming language developed by Apple Inc. and the open-source community. Swift compiles to machine code, as it is an LLVM-based compiler. Swift was first released in June 2014, and the Swift toolchain has shipped in Xcode since version 6, released in 2014.

<span class="mw-page-title-main">Nim (programming language)</span> Programming language

Nim is a general-purpose, multi-paradigm, statically typed, compiled high-level systems programming language, designed and developed by a team around Andreas Rumpf. Nim is designed to be "efficient, expressive, and elegant", supporting metaprogramming, functional, message passing, procedural, and object-oriented programming styles by providing several features such as compile time code generation, algebraic data types, a foreign function interface (FFI) with C, C++, Objective-C, and JavaScript, and supporting compiling to those same languages as intermediate representations.

Whiley is an experimental programming language that combines features from the functional and imperative paradigms, and supports formal specification through function preconditions, postconditions and loop invariants. The language uses flow-sensitive typing also known as "flow typing."

References

  1. ↑ King, Gavin. "The Ceylon Language: §4.1 Compilation unit structure" . Retrieved 2015-12-04. A compilation unit is a text file, with the filename extension .ceylon.
  2. ↑ "Frequently Asked Questions: What is Ceylon?" . Retrieved 2015-12-04. Ceylon is a new programming language that's deeply influenced by Java
  3. ↑ "ceylon/user - Gitter" . Retrieved 2015-12-04.
  4. ↑ "ceylon/user - Gitter" . Retrieved 2015-12-04.
  5. ↑ "Top 10 Ceylon language features Java wishes it had" . Retrieved 2019-11-29.
  6. ↑ "Ceylon 1.0 beta" . Retrieved 2013-09-26.
  7. ↑ "Project Ceylon – Red Hat builds Java replacement". The Register. 2011-04-13. Retrieved 2011-11-27.
  8. ↑ King, Gavin (2012-01-10). "Principles that guide this project" . Retrieved 2015-12-04.
  9. ↑ "FAQ about language design: Goals" . Retrieved 2015-12-04.
  10. ↑ Festal, David (2014-10-10). "Write in Ceylon, deploy as OSGI, use in Java EE" . Retrieved 2015-12-04.
  11. ↑ "Maven repositories" . Retrieved 2015-12-04.
  12. ↑ "Features of Ceylon IDE" . Retrieved 2015-12-04.
  13. ↑ "ceylon / ceylon". GitHub, Inc. 2020-05-25. Archived from the original on 2023-10-03. Retrieved 2024-01-22.
  14. ↑ "Eclipse Ceylon™ Termination Review". Eclipse Foundation. 2023-04-05. Archived from the original on 2023-04-23. Retrieved 2023-04-23.
  15. ↑ King, Gavin. "Ceylon: Language Design FAQ".
  16. ↑ King, Gavin. "The Ceylon Language: §1.4.3 Compile-time safety for null values and flow-sensitive typing" . Retrieved 2015-12-04.
  17. ↑ King, Gavin. "The Ceylon Language: 4.7 Functions" . Retrieved 5 December 2015.
  18. ↑ King, Gavin. "The Ceylon Language: 4.5.8 Enumerated classes" . Retrieved 6 December 2015.
  19. ↑ King, Gavin. "The Ceylon Language: §3.2.9 Type inference" . Retrieved 2015-12-04.
  20. ↑ https://ceylon-lang.org/download-archive/ Ceylon: Download Previous Ceylon versions
  21. ↑ "Ceylon: Licenses" . Retrieved 2015-12-04.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.