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| </div><div id='content' class='page-1'><div class='row'><div class='row-fluid'><div class='col-lg-3'><ul class='nav-sidebar'><li><a href='./'>Blog index</a></li><li class='active'><a href='#doc'>Set Operators with Groovy</a></li></ul><br/><ul class='nav-sidebar'><li style='padding: 0.35em 0.625em; background-color: #eee'><span>Related posts</span></li><li><a href='./helloworldemoji'>Hello World with Emojis</a></li><li><a href='./deep-learning-and-eclipse-collections'>Deep Learning and Eclipse Collections</a></li><li><a href='./adventures-with-groovyfx'>Adventures with GroovyFX</a></li><li><a href='./fruity-eclipse-collections'>Fruity Eclipse Collections</a></li><li><a href='./zipping-collections-with-groovy'>Zipping Collections with Groovy</a></li></ul></div><div class='col-lg-8 col-lg-pull-0'><a name='doc'></a><h1>Set Operators with Groovy</h1><p><span>Author: <i>Paul King</i></span><br/><span>Published: 2023-11-14 03:22PM</span></p><hr/><div class="paragraph"> |
| <p><a href="https://twitter.com/TheDonRaab">Donald Raab</a> posted <a href="https://donraab.medium.com/comparing-set-operations-between-java-and-eclipse-collections-92cf1df28d3b">an article</a> about set operators using Java collections and <a href="https://github.com/eclipse/eclipse-collections">Eclipse Collections</a>. <a href="https://donraab.medium.com/comparing-set-operations-between-java-and-eclipse-collections-92cf1df28d3b">That post</a> focuses |
| on the <em>union</em>, <em>intersection</em> and <em>difference</em> operators. We’ll add in |
| <em>symmetric difference</em> since Groovy supports operator overloading for that |
| operator also.</p> |
| </div> |
| <div class="paragraph"> |
| <p>First, a quick refresh about the operators for two sets <strong>A</strong> and <strong>B</strong>:</p> |
| </div> |
| <div class="paragraph"> |
| <p><span class="image"><img src="img/SetOperators.png" alt="SetOperators"></span></p> |
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| <div class="paragraph"> |
| <p>We’ll use the same emoji sets from Donald’s post:</p> |
| </div> |
| <div class="listingblock"> |
| <div class="content"> |
| <pre class="prettyprint highlight"><code data-lang="groovy">Set OCT = ["🍁", "🍃", "🎃", "🥧", "🍫", "🌝", "👻", "🌽", "🍎", "🪵", "☕️"] |
| Set NOV = ["🍂", "🍁", "🥧", "🦃", "🌽", "🍎", "🪵", "☕️"] |
| Set DEC = ["🥧", "🦃", "⛄️", "🍎", "🌰", "🛷", "🪵", "🎄", "☕️"]</code></pre> |
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| <div class="paragraph"> |
| <p>Groovy lets you write the same code as in Donald’s post but also offers |
| operator overloading for these operators as follows:</p> |
| </div> |
| <div class="listingblock"> |
| <div class="content"> |
| <pre class="prettyprint highlight"><code data-lang="groovy">assert (OCT & NOV & DEC) == ["🪵", "🥧", "🍎", "☕️"] as Set |
| |
| assert (OCT | NOV | DEC) == ["🪵", "🦃", "🌰", "🛷", "🍎", "🎄", |
| "🍫", "🌝", "☕️", "🥧", "⛄️", "🍁", |
| "🍂", "🍃", "👻", "🌽", "🎃"] as Set |
| |
| assert (OCT - NOV - DEC) == ["🍫", "🌝", "🍃", "👻", "🎃"] as Set |
| assert (NOV - OCT - DEC) == ["🍂"] as Set |
| assert (DEC - OCT - NOV) == ["🎄", "🌰", "⛄️", "🛷"] as Set |
| |
| assert (OCT ^ NOV ^ DEC) == ['⛄️', '🌰', '🛷', '🎄', '🍃', '🎃', '🍫', '🌝', |
| '👻', '🍂', '🥧', '🍎', '🪵', '☕️'] as Set |
| assert (NOV ^ OCT ^ DEC) == ['🍂', '🍃', '🎃', '🍫', '🌝', '👻', '🥧', '⛄️', |
| '🍎', '🌰', '🛷', '🪵', '🎄', '☕️'] as Set</code></pre> |
| </div> |
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| <div class="paragraph"> |
| <p>This code is using standard mutable Java collections, |
| but we could use the normal <code>Set.of(…​)</code> form and work with immutable sets |
| if that was our preference.</p> |
| </div> |
| <div class="paragraph"> |
| <p>Also, since the Eclipse Collections Set implementations implement |
| the standard Java <code>Set</code> interface, these operator overloading shorthands |
| also work when using Eclipse Collections. We simply use |
| <code>Sets.immutable.of(…​)</code> in our set definitions.</p> |
| </div> |
| <div class="paragraph"> |
| <p>What’s more, since Groovy operator overloading is extensible, you can have similar |
| shorthand notation for your own domain objects also. Enjoy!</p> |
| </div> |
| <div class="paragraph"> |
| <p>This example used an alpha version of Groovy 5. Groovy 5 adds a little bit |
| of extra syntactic sugar when using sets. Earlier versions of Groovy |
| have <code>union</code> and <code>intersect</code> methods for sets.</p> |
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