Editing Sather

{{Short description|Object-oriented programming language similar to Eiffel}}
{{About||people with the surname|Sather (surname)}}
{{Infobox programming language
|name = Sather
|logo =
|paradigm = [[Object-oriented programming|object-oriented]], [[Functional programming|functional]]
|family = [[Eiffel (programming language)|Eiffel]]
|designer = [[Steve Omohundro]]
|developer = [[University of California, Berkeley]], [[University of Waikato]], [[GNU project]]
|released = {{Start date and age|1990}}
|latest release version = {{wikidata|property|reference|P348}}
|latest release date = {{start date and age|{{wikidata|qualifier|P348|P577}}}}
|typing = [[static typing|static]], [[Strong and weak typing|strong]]
|implementations = ICSI Sather, GNU Sather
|dialects =
|influenced by = [[Eiffel (programming language)|Eiffel]], [[CLU (programming language)|CLU]], [[Common Lisp]], [[Scheme (programming language)|Scheme]]
|influenced = Cool
}}

'''Sather''' is an [[Object-oriented programming|object-oriented]] [[programming language]]. It originated circa 1990 at the International Computer Science Institute (ICSI) at the [[University of California, Berkeley]], developed by an international team led by [[Steve Omohundro]]. It supports [[Garbage collection (computer science)|garbage collection]] and [[Generic programming|generics]] by [[Subtyping|subtypes]].

Originally, it was based on [[Eiffel (programming language)|Eiffel]], but it has diverged, and now includes several [[functional programming]] features.

The name is inspired by Eiffel; the [[Sather Tower]] is a recognizable landmark at Berkeley, named after [[Jane Krom Sather]], the widow of [[Peder Sather]], who donated large sums to the foundation of the university.

Sather also takes inspiration from other programming languages and paradigms: [[iterator]]s, [[design by contract]], [[abstract class]]es, [[multiple inheritance]], [[anonymous function]]s, [[operator overloading]], [[Covariance and contravariance (computer science)|contravariant]] type system.

The original Berkeley implementation (last stable version 1.1 was released in 1995, no longer maintained<ref>{{cite web| url = http://www.icsi.berkeley.edu/~sather/future.html| title = ICSI Sather future plans| access-date = 2012-03-02| archive-date = 2012-02-05| archive-url = https://web.archive.org/web/20120205024842/http://www.icsi.berkeley.edu/~sather/future.html| url-status = live}}</ref>) has been adopted by the [[Free Software Foundation]] therefore becoming GNU Sather. Last stable GNU version (1.2.3) was released in July 2007<ref>{{cite web| url = http://ftp.gnu.org/gnu/sather/| title = GNU Sather downloads| access-date = 2012-03-02| archive-date = 2012-04-05| archive-url = https://web.archive.org/web/20120405211902/http://ftp.gnu.org/gnu/sather/| url-status = live}}</ref> and the software is currently not maintained. There were several other variants: Sather-K from the [[University of Karlsruhe]];<ref>[https://web.archive.org/web/20011202073442/http://i44s11.info.uni-karlsruhe.de/sather/ Sather-K  project page] (archive from year 2001)</ref><ref>{{cite web| url = ftp://ftp.icsi.berkeley.edu/pub/sather/Sather-K/| archive-url = https://web.archive.org/web/20240429011023/ftp://ftp.icsi.berkeley.edu/pub/sather/Sather-K/| archive-date = 2024-04-29| url-status = dead| title = Sather-K 0.9 download, version from year 1994| access-date = 2012-03-02}}</ref> Sather-W from the [[University of Waikato]]<ref>[https://web.archive.org/web/20021213090342/http://www.cs.waikato.ac.nz/sather/ Sather-W 1.3 project page] (archived link from year 2002)</ref> (implementation of Sather version 1.3); Peter Naulls' port of ICSI Sather 1.1 to [[RISC OS]];<ref>Peter Naulls' port is no longer available on the Web.</ref> and pSather,<ref>{{cite web| url = http://www.icsi.berkeley.edu/~sather/psather.html| title = pSather description| access-date = 2012-03-02| archive-date = 2012-02-05| archive-url = https://web.archive.org/web/20120205024939/http://www.icsi.berkeley.edu/~sather/psather.html| url-status = live}}</ref><ref>{{cite web| url = ftp://ftp.icsi.berkeley.edu/pub/sather| archive-url = https://web.archive.org/web/20170706110058/ftp://ftp.icsi.berkeley.edu/pub/sather| archive-date = 2017-07-06| url-status = dead| title = pSather download| access-date = 2021-10-11}}</ref> a parallel version of ICSI Sather addressing [[non-uniform memory access]] multiprocessor architectures but presenting a shared memory model to the programmer.

The former ICSI Sather compiler (now GNU Sather) is implemented as a compiler to [[C (programming language)|C]], i.e., the compiler does not output [[object file|object]] or [[Machine language|machine]] code, but takes Sather [[source code]] and generates C source code as an [[intermediate language]]. Optimizing is left to the C compiler.

The GNU Sather compiler, written in Sather itself, is [[dual licensed]] under the GNU [[GNU General Public License|GPL]] & [[LGPL]].

== Hello World ==
<syntaxhighlight lang="eiffel" line>
 class HELLO_WORLD is
  main is 
   #OUT+"Hello World\n"; 
  end; 
 end;
</syntaxhighlight>
A few remarks:
* Class names are ALL CAPS; this is not only a convention but it's enforced by the compiler.
* The method called <code>main</code> is the entry point for execution. It may belong to any class, but if this is different from <code>MAIN</code>, it must be specified as a compiler option.
* <code>#</code> is the constructor symbol: It calls the <code>create</code> method of the class whose name follows the operator. In this example, it's used for instantiating the <code>OUT</code> class, which is the class for the [[Standard streams#Standard_output_(stdout)|standard output]].
* The <code>+</code> operator has been overloaded by the class to append the string passed as argument to the stream.
* Operators such as <code>+</code> are [[syntactic sugar]] for conventionally named method calls: <code>a + b</code> stands for <code>a.plus(b)</code>. The usual arithmetic precedence conventions are used to resolve the calling order of methods in complex formulae.

== Example of iterators ==

This program prints numbers from 1 to 10.

<syntaxhighlight lang="eiffel" line>
 class MAIN is
   main is
     loop
      i := 1.upto!(10);
      #OUT + i + "\n";
     end;
   end;
 end;
</syntaxhighlight>

The <code>loop</code> ... <code>end</code> construct is the preferred means of defining loops, although <code>while</code> and <code>repeat</code>-<code>until</code> are also available. Within the construct, one or more iterators may be used. Iterator names always end with an exclamation mark. (This convention is enforced by the compiler.) <code>upto!</code> is a method of the <code>INT</code> class accepting one <code>once</code> argument, meaning its value won't change as the iterator yields. <code>upto!</code> could be implemented in the <code>INT</code> class with code similar to the following one.

<syntaxhighlight lang="eiffel">
  upto!(once m:INT):SAME is
    i: INT := self; -- initialise i to the value of self, 
                    -- that is the integer of which this method is called
    loop
      if i>m then 
        quit;  -- leave the loop when i goes beyond m
      end;
      yield i; -- else use i as return value and stay in the loop
      i := i + 1; -- and increment
    end;
  end;
</syntaxhighlight>

Type information for variables is denoted by the postfix syntax <code>variable:CLASS</code>. The type can often be inferred and thus the typing information is optional, as in <code>anInteger::=1</code>. <code>SAME</code> is a pseudo-class referring to the current class.

==References==
{{reflist}}

==External links==
{{cite web |title=Sather Home Page |url=http://www.icsi.berkeley.edu/~sather/ |archive-url=https://web.archive.org/web/20240325214242/https://www1.icsi.berkeley.edu/~sather/ |archive-date=2024-03-25 |access-date=2025-01-16}}
[[Category:Class-based programming languages]]
[[Category:GNU Project software]]