Ceylon (programming language): Difference between revisions

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{{Short description|None}}

≈{{primary sources|date=January 2017}}

{{Infobox programming language

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| paradigm = [[Object-oriented programming|Object-oriented]]

| designer = Gavin King

| developer = [[RedEclipse HatFoundation]]

| released = {{Start date and age|2011}}

| latest release version = 1.3.23

| latest release date = {{Start date and age|2017|0308|0321}}

| typing = [[TypeStatic type system|Static]], [[Strong and weak typing|strong]], [[Type safety|safe]]

| scope =

| programming language =

| platform = [[Virtual machine|VMs]] of [[Java virtual machine|Java]], [[JavaScript]]

| operating system =

| license = [[Apache License|Apache 2.0]] v2

| website = {{URL|ceylon-lang.org}}

| file ext = .ceylon<ref>{{cite web

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| url=https://gitter.im/ceylon/user?at=5660a7242cbea1d7054de9d9

| title=ceylon/user - Gitter

| access-date=2015-12-04}}</ref> [[Lisp (programming language)|Lisp]],<ref>{{cite web

| url=https://gitter.im/ceylon/user?at=5660a90e5057376520db6f8b

| title=ceylon/user - Gitter

| access-date=2015-12-04}}</ref> [[Whiley (programming language)|Whiley]]<ref>{{cite web

| url=https://jaxenter.com/top-10-ceylon-language-features-java-wishes-it-had-108003.html

| access-date=2019-11-29

| title=Top 10 Ceylon language features Java wishes it had}}</ref>

| influenced =

| wikibooks =

}}

'''Ceylon''' iswas an [[Object-oriented programming|object-oriented]], [[Strong typing|strongly]] [[Type system|statically typed]] programming language with an emphasis on [[Immutable object|immutability]], created by [[Red Hat]], the "Ceylon" compiler. Ceylon programs run on the [[Java virtual machine]] (JVM), and cancould be compiled to [[JavaScript]].<ref>{{cite web

| url=http://ceylon-lang.org/blog/2013/09/22/ceylon-1/

| title=Ceylon 1.0 beta

| access-date=2013-09-26}}</ref><ref>{{cite web

| url=httphttps://www.theregister.co.uk/2011/04/13/red_hat_unveils_project_ceylon

| title=Project Ceylon – Red Hat builds Java replacement

| date=2011-04-13

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| title=FAQ about language design: Goals

| access-date=2015-12-04}}</ref>

* A type system enforcing [[null safety]] and list element existence at compile time

* Regular syntax and semantics, avoiding special cases and primitively- defined constructs in favor of [[syntactic sugar]]

* Support for generic programming and metaprogramming, with [[Reification (computer science)|reified]] [[Parametric polymorphism|generics]]

* Modularity built into the language, based on [[WildFly|JBoss modules]], interoperable with [[OSGi]]<ref>{{cite web

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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.<ref>{{cite web

|date=2020-05-25

|title= ceylon / ceylon

|publisher=GitHub, Inc.

|url=https://github.com/eclipse-archived/ceylon

|access-date=2024-01-22

|archive-url=https://web.archive.org/web/20231003075404/https://github.com/eclipse-archived/ceylon

|archive-date=2023-10-03

|url-status=live}}

</ref> In April 2023, [[Eclipse Foundation]] declared the termination of the transition.<ref>{{cite web

|date=2023-04-05

|title= Eclipse Ceylon™ Termination Review

|publisher=Eclipse Foundation

|url=https://projects.eclipse.org/projects/technology.ceylon/reviews/termination-review

|access-date=2023-04-23

|archive-url=https://web.archive.org/web/20230423134055/https://projects.eclipse.org/projects/technology.ceylon/reviews/termination-review

|archive-date=2023-04-23

|url-status=live}}</ref>

== Language features ==

Ceylon is heavily- influenced by [[Java (programming language)|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<ref>{{cite web|last1=King|first1=Gavin|title=Ceylon: Language Design FAQ|url=http://ceylon-lang.org/documentation/faq/language-design/}}</ref> and [[Object type|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 typestype]]s, in a similar fashion to [[TypeScript]], [[Whiley (programming language)|Whiley]] and Flow, which in fact, took the idea from Ceylon.

Union types, written <code>A|B</code>, allow a variable to have more than one type. The following example shows a Ceylon function which may take either an [[Integer (computer science)|integer]] or a [[String (computer science)|string]]:

<sourcesyntaxhighlight lang="ceylon">

shared void integerOrString(Integer|String input) {

if (is Integer input) {

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}

}

</syntaxhighlight>

</source>

Intersection types, written <code>A&B</code>, are the theoretical foundation of [[flow-sensitive typing]]:

<sourcesyntaxhighlight lang="ceylon">

shared void integerOrString(Integer|String input) {

Integer added = input + 6; // illegal; the + operator is not defined on Integer|String

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}

}

</syntaxhighlight>

</source>

The condition <code>is Integer input</code> narrows the type of <code>input</code> to <code>&lt;Integer|String&gt; &amp; Integer</code>,

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==== Null safety ====

Union and intersection types are used to provide [[null safety]].

The top type of the Ceylon type hierarchy is the class <code>Anything</code>,

which has two subclasses: <code>Object</code>, the superclass of all normal classes and all interfaces, and <code>Null</code>, with the only instance [[Null pointer|<code>null</code>]].

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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 <code>null</code> elements from a stream of values could be:

<sourcesyntaxhighlight lang="ceylon">

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

</syntaxhighlight>

</source>

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

==== Functions ====

Similarly to many modern languages, Ceylon supports [[first class functionsfunction]]s and [[higher order functionsfunction]]s, including function types and [[anonymous functions function]]s<ref>{{cite web|last=King|first=Gavin|title=The Ceylon Language: 4.7 Functions |url=http://ceylon-lang.org/documentation/1.2/spec/html/declarations.html#functions|access-date=5 December 2015}}</ref>

<sourcesyntaxhighlight lang="ceylon">

// A top-level higher-order function using block syntax (not associated with any user-created classes)

String process(String text, String transformString(String toChange)) {

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String reversed1 = process("one", reverse);

// AnyAn example where an anonymous function - (text) => text+text - is provided to the higher-order function above.

String reversed2 = process("one", (text) => text+text);

</syntaxhighlight>

</source>

==== Enumerated types ====

Similar to Java and many other languages, and with a similar mechanism as [[Algebraic data type|algebraic types]], Ceylon supports [[enumerated typestype]]s, 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.<ref>{{cite web|last=King|first=Gavin|title=The Ceylon Language: 4.5.8 Enumerated classes |url=http://ceylon-lang.org/documentation/1.2/spec/html/declarations.html#classeswithcases|access-date=6 December 2015}}</ref>

<sourcesyntaxhighlight lang="ceylon">

// Traditional syntax for enumerated type, in this case, limiting the instances to three objects(for this purpose: Singletons)

abstract class Vehicle(shared String name) of plane | train | automobile {}

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//shared new boat extends named("boat") {}

}

</syntaxhighlight>

</source>

==== Type inference ====

Ceylon is strongly and statically typed, but also has support for [[type inference]].

The <code>value</code> keyword is used to infer the type of a variable,

and the <code>function</code> keyword is used to infer the type of a function.

The following two definition pairs are each equivalent:

<sourcesyntaxhighlight lang="ceylon">

Integer i = 3;

value i = 3;

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return i1 + i2;

}

</syntaxhighlight>

</source>

However, to make single-pass type inference possible, type inference is only allowed for non-toplevel and unshared declarations.<ref>{{cite web

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=== Entry point with names===

By default the starter (<code>ceylon run</code>) runs the shared run() function of a module:

<sourcesyntaxhighlight lang="ceylon">

/* The classic Hello World program */

shared void run() {

print("Hello, World!");

}

</syntaxhighlight>

</source>

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

<code>ceylon run --compile=force --run hello default</code>

== Versions ==

Versions of Ceylon released:<ref>https://ceylon-lang.org/download-archive/ Ceylon: Download Previous Ceylon versions</ref>

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* M1 0.1 "Newton" (Dec 20 2011)

* M2 0.2 "Minitel" (Mar 2 2012)

* M3 0.3 "V2000" (Jun 21 2012)

* M3.1 0.3.1 "V2000" (Jul 6 2012)

* M4 0.4 "Analytical Engine" (Oct 29 2012)

* M5 0.5 "Nesa Pong" (Mar 13 2013)

* M6 0.6 "Virtual Boy" (Sep 23 2013)

* 1.0 beta "Virtual Boy" (Sep 24 2013)

* 1.0.0 "No More Mr Nice Guy" (Nov 13 2013)

* 1.1.0 "Ultimate Ship The Second" (Oct 09 2014)

* 1.2.0 "A Series of Unlikely Explanations" (Oct 28 2015)

* 1.2.1 "Irregular Apocalypse" (Feb 11 2016)

* 1.2.2 "Charming But Irrational" (Mar 11 2016)

* 1.3.0 "Total Internal Reflection" (Sep 19 2016)

* 1.3.1 "Now We Try It My Way" (Nov 22 2016)

* 1.3.2 "Smile Tolerantly" (Mar 02 2017)

* 1.3.3 "Contents May Differ" (Aug 21 2017)

== License ==

All parts of Ceylon are available underas open[[free source licensessoftware]], mostly the [[Apache License]].<ref>{{cite web

| url=http://ceylon-lang.org/code/licenses

| title=Ceylon: Licenses

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[[Category:Java programming language family]]

[[Category:JVM programming languages]]

[[Category:Programming languages created in 2011]]

[[Category:Red Hat software]]

[[Category:Software using the Apache license]]

[[Category:Programming2011 languages created in 2011software]]

[[Category:High-level programming languages]]

[[Category:Source-to-source compilers]]