Eiffel Community

<!doctype html> <html> <head> <meta charset="utf-8"/> <meta name="viewport" content="width=device-width, initial-scale=1"/> <title>Eiffel Community</title> <link media="all" rel="stylesheet" href="/theme/responsive-eiffel-org/css/all.css" /> <link rel="shortcut icon" href="https://www.eiffel.org/favicon.ico"/> <link href="https://fonts.googleapis.com/css?family=Inconsolata|Open+Sans:400,700|Titillium+Web" rel="stylesheet" type="text/css" />  <script src="https://ajax.googleapis.com/ajax/libs/jquery/1.12.4/jquery.min.js"></script> <link rel="stylesheet" href="/module/auth/files/css/auth.css" type="text/css"/> <link rel="stylesheet" href="/module/node/files/css/node.css" type="text/css"/> <link rel="stylesheet" href="/module/blog/files/css/blog.css" type="text/css"/> <link rel="stylesheet" href="/module/comments/files/css/comments.css" type="text/css"/> <link rel="stylesheet" href="/module/wikitext/files/css/wikitext.css" type="text/css"/> <link rel="stylesheet" href="/module/taxonomy/files/css/taxonomy.css" type="text/css"/> <style> table.recent-changes th { padding: 3px; } table.recent-changes td { padding: 3px; border: dotted 1px #ddd; } table.recent-changes td.date { padding-left: 15px; } table.recent-changes td.title { font-weight: bold; } </style> <link rel="stylesheet" href="/module/feed_aggregator/files/css/feed_aggregator.css" type="text/css"/> <link rel="profile" href="http://gmpg.org/xfn/11" /> <meta property="url" content="https://www.eiffel.org/" /> <meta property="description" content="Welcome to the community portal for Eiffel, the programming language for tackling tomorrow’s problems today." /> <meta property="keywords" content="[eiffel,community,programming,language,design,contract,dbc,object,oo]" /> <meta property="og:type" content="website" /> <meta property="og:image" content="https://www.eiffel.org/favicon.ico" /> <link rel='canonical' href='https://www.eiffel.org/' /> <link rel='shortlink' href='https://www.eiffel.org/' /> <script type="text/javascript" src="/module/wdocs/files/js/wdocs.js"></script> <link rel="stylesheet" href="/module/wdocs/files/css/wdocs.css" type="text/css"/> </head> <body class="page"> <div id="page">  <header id="header" class="grid-3"> <div class="logo"><a href="https://www.eiffel.org/"><img src="/theme/responsive-eiffel-org/images/logo.png" width="226" height="60" alt="Eiffel"></a></div> <nav id="nav"> <ul> <li><a href="https://www.eiffel.org/welcome">welcome</a></li> <li><a href="https://www.eiffel.org/documentation">documentation</a></li> <li><a href="https://www.eiffel.org/resources">resources</a></li> <li><a href="https://www.eiffel.org/contribute">contribute</a></li> <li><a href="https://www.eiffel.org/blogs">blogs</a></li> <li><a href="https://www.eiffel.org/downloads">download</a></li> </ul> </nav> <nav class="add-links"> <ul> <li> <a href="/account/roc-login?destination=">Sign in</a> </li> <li class="search"> <div class="block" id="block-gcse_search_form"><div class="inside"><form class="search-form" method="GET" action="https://www.eiffel.org/gcse20"> <input type="image" alt="Search" class="btn" src="/theme/responsive-eiffel-org/images/ico-search.png"/> <input type="text" name="q" size="25" maxlength="255" value="" /> </form> </div></div> </li> </ul> </nav> </header>  <main id="main"> <a id="main-content"></a> <section class="jumbotron"> <div class="container"> <div class="grid-2"> <div class="col"><div class="block" id="block-codeboard_demo"><div class="inside"><div class="codeboard-demo"> <div class="btn-holder"><a class="btn-play" href="codeboard">Try Eiffel online</a></div> <div class="codeboard-player"> <link rel="stylesheet" property="stylesheet" href="/module/codeboard/files/css/codeboard_static_demo.css"/> <div class="slider-wrapper"> <div class="slider" data-slider-delay="7000"> <input type="radio" name="slider" class="trigger" id="slide1" checked="checked" /> <div class="slide"> <div class="slide-item"> <pre class="prettyprint lang-eiffel"> io.put_string_32 ("[ Hello! Â¡Hola! Bonjour! こんにちは！ Здравствуйте! Γειά σου! ]")</pre> <p class="slide-caption"> Unicode output in console </p> </div> </div> <input type="radio" name="slider" class="trigger" id="slide2" /> <div class="slide"> <div class="slide-item"> <pre class="prettyprint lang-eiffel">feature -- Access ... invariant all_items_valid: ∀ x: items ¦ x.is_valid at_least_one_marked: ∃ x: items ¦ x.is_marked end</pre> <p class="slide-caption"> Assertions: class invariants with symbolic notation </p> </div> </div> <input type="radio" name="slider" class="trigger" id="slide3" /> <div class="slide"> <div class="slide-item"> <pre class="prettyprint lang-eiffel"> values := << 1, 2, 4, 8 >> -- Sum of (index * values [index]). across values as i from sum := 0 loop sum := sum + i.cursor_index * i.item end</pre> <p class="slide-caption"> <a href="https://codeboard.eiffel.org/projects/4"> Sum using across loop </a> </p> </div> </div> <input type="radio" name="slider" class="trigger" id="slide4" /> <div class="slide"> <div class="slide-item"> <pre class="prettyprint lang-eiffel"> rating := locale.plural_translation_in_context ("$1 star", "$1 stars", "example.context", n) ... rating: READABLE_STRING_32 -- Translated message. locale: I18N_LOCALE -- Currently selected locale with translations. do ... end</pre> <p class="slide-caption"> <a href="https://www.eiffel.org/files/doc/static/trunk/libraries/i18n/i18n_locale_flatshort.html#f_plural_translation_in_context"> Internationalization </a> </p> </div> </div> <input type="radio" name="slider" class="trigger" id="slide5" /> <div class="slide"> <div class="slide-item"> <pre class="prettyprint lang-eiffel">class DINING_PHILOSOPHER ... feature -- Basic operations eat (left, right: separate FORK) -- Race-free access to the forks `left` and `right`. do left.use right.use end end</pre> <p class="slide-caption"> <a href="https://codeboard.eiffel.org/projects/5"> Concurrency with SCOOP </a> </p> </div> </div> <input type="radio" name="slider" class="trigger" id="slide6" /> <div class="slide"> <div class="slide-item"> <pre class="prettyprint lang-eiffel">feature -- Access balance: INTEGER -- Current balance in dollars. feature -- Element change withdraw (amount: INTEGER) -- Remove `amount` dollars. require positive: amount > 0 not_too_big: amount <= balance do balance := balance - amount ensure increased: balance = old balance - amount end</pre> <p class="slide-caption"> <a href="https://codeboard.eiffel.org/projects/6"> Bank account example </a> </p> </div> </div> <input type="radio" name="slider" class="trigger" id="slide7" /> <div class="slide"> <div class="slide-item"> <pre class="prettyprint lang-eiffel">run -- Execute tasks from `pool`. do from until not attached retrieved_task (pool) as task loop separate task as t do t.call end end end</pre> <p class="slide-caption"> <a href="https://codeboard.eiffel.org/projects/7"> Running a pool of tasks </a> </p> </div> </div> <input type="radio" name="slider" class="trigger" id="slide8" /> <div class="slide"> <div class="slide-item"> <pre class="prettyprint lang-eiffel">class REFEREE: race_start.publish (create {DATE_TIME}.make_now_utc) class RACE_CONTROL: race_start: EVENT_TYPE [DATE_TIME] class SPRINTER: race_start.subscribe (agent run_from_now) run_from_now (t: DATE_TIME) -- Record `t` as starting time and get running. do start_time := t run end</pre> <p class="slide-caption"> Event-based programming with agents </p> </div> </div> </div> <ul class="slider-nav"> <li class="slider-nav__item"><label class="slider-nav__label" for="slide1">1</label></li> <li class="slider-nav__item"><label class="slider-nav__label" for="slide2">2</label></li> <li class="slider-nav__item"><label class="slider-nav__label" for="slide3">3</label></li> <li class="slider-nav__item"><label class="slider-nav__label" for="slide4">4</label></li> <li class="slider-nav__item"><label class="slider-nav__label" for="slide5">5</label></li> <li class="slider-nav__item"><label class="slider-nav__label" for="slide6">6</label></li> <li class="slider-nav__item"><label class="slider-nav__label" for="slide7">7</label></li> <li class="slider-nav__item"><label class="slider-nav__label" for="slide8">8</label></li> </ul> </div> <script type="text/javascript" src="/module/codeboard/files/codeboard_static_demo.js"></script> </div> </div> </div></div></div> <div class="col"></div> </div> </div> </section>  <section class="rss-block"> <div class="container"> <h1>Recent posts</h1> <ul> <li><h2>News</h2><div class="roccms-load" data-href="/feed_aggregation/news?view=embedded&size=7"></div></li> <li><h2>Forum</h2><div class="roccms-load" data-href="/feed_aggregation/forum?view=embedded&size=7"></div></li> <li><h2>Facebook</h2> <div id="fb-root"></div> <script> (function(d, s, id) { var js, fjs = d.getElementsByTagName(s)[0]; 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