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<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<meta name="generator" content="pandoc">
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</style>
<link rel="stylesheet" href="exercise-style.css">
</head>
<body>
<h1 id="ownership">Ownership</h1>
<p>(Time: 10 minutes)</p>
<ul>
<li><p>Goal #1: Get code below (<a href="https://play.rust-lang.org/?code=fn%20main%28%29%20%7B%0A%20%20%20%20let%20%28adjective%2C%20name%29%20%3D%20two_words%28%29%3B%0A%20%20%20%20let%20name%20%3D%20format%21%28%22%7B%7D%20%7B%7D%22%2C%20adjective%2C%20name%29%3B%0A%20%20%20%20print_out%28name%29%3B%0A%7D%0A%0Afn%20two_words%28%29%20-%3E%20%28String%2C%20String%29%20%7B%0A%20%20%20%20%28format%21%28%22fellow%22%29%2C%20format%21%28%22Rustaceans%22%29%29%0A%7D%0A%0Afn%20remove_vowels%28name%3A%20String%29%20-%3E%20String%20%7B%0A%20%20%20%20%2F%2F%20Goal%20%231%3A%20What%20is%20needed%20here%20to%20make%20this%20compile%3F%0A%20%20%20%20let%20output%20%3D%20String%3A%3Anew%28%29%3B%0A%20%20%20%20for%20c%20in%20name.chars%28%29%20%7B%0A%20%20%20%20%20%20%20%20match%20c%20%7B%0A%20%20%20%20%20%20%20%20%20%20%20%20%27a%27%20%7C%20%27e%27%20%7C%20%27i%27%20%7C%20%27o%27%20%7C%20%27u%27%20%3D%3E%20%7B%0A%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%2F%2F%20skip%20vowels%0A%20%20%20%20%20%20%20%20%20%20%20%20%7D%0A%20%20%20%20%20%20%20%20%20%20%20%20_%20%3D%3E%20%7B%0A%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20output.push%28c%29%3B%0A%20%20%20%20%20%20%20%20%20%20%20%20%7D%0A%20%20%20%20%20%20%20%20%7D%0A%20%20%20%20%7D%0A%20%20%20%20output%0A%7D%0A%0Afn%20print_out%28name%3A%20String%29%20%7B%0A%20%20%20%20let%20devowelized_name%20%3D%20remove_vowels%28name%29%3B%0A%20%20%20%20println%21%28%22Removing%20vowels%20yields%20%7B%3A%3F%7D%22%2C%20devowelized_name%29%3B%0A%0A%20%20%20%20%2F%2F%20Goal%20%232%3A%20What%20happens%20when%20you%20uncomment%20the%20following%0A%20%20%20%20%2F%2F%20line%3F%20Can%20you%20change%20the%20code%20above%20so%20that%20this%20next%20line%3F%0A%20%20%20%20%2F%2F%20println%21%28%22Removing%20vowels%20from%20%7B%3A%3F%7D%20yields%20%7B%3A%3F%7D%22%2C%0A%20%20%20%20%2F%2F%20%20%20%20%20%20%20%20%20%20name%2C%20devowelized_name%29%3B%0A%0A%20%20%20%20%2F%2F%20Extra%20credit%3A%20Can%20you%20do%20it%20without%20copying%20any%20data%3F%0A%20%20%20%20%2F%2F%20%28Using%20only%20ownership%20transfer%29%0A%7D&version=nightly">playpen</a>) to compile.</p></li>
<li><p>Goal #2: Convert the code so that it prints <code>Removing vowels from "Rustaceans" yields "Rstcns"</code>.</p></li>
<li><p>Extra-credit: Can you accomplish the previous goal without copying any data (e.g. no calls to <code>.clone()</code>).</p></li>
<li><p>Goal #3: This code is sound, but it is still buggy; identify and fix the bug. Hint: <a><span id="hint1" class="hint" onclick="var h = document.getElementById('hint1'); h.style.color = (h.style.color == 'inherit') ? 'transparent' : 'inherit';">What happens if you pass <code>"SNOBOL Throwers"</code> instead?</span></a></p></li>
</ul>
<div class="sourceCode"><pre class="sourceCode rust"><code class="sourceCode rust"><span class="kw">fn</span> main() {
<span class="kw">let</span> (adjective, name) = two_words();
<span class="kw">let</span> name = <span class="pp">format!</span>(<span class="st">"{} {}"</span>, adjective, name);
print_out(name);
}
<span class="kw">fn</span> two_words() -> (<span class="dt">String</span>, <span class="dt">String</span>) {
(<span class="pp">format!</span>(<span class="st">"fellow"</span>), <span class="pp">format!</span>(<span class="st">"Rustaceans"</span>))
}
<span class="kw">fn</span> remove_vowels(name: <span class="dt">String</span>) -> <span class="dt">String</span> {
<span class="co">// Goal #1: What is needed here to make this compile?</span>
<span class="kw">let</span> output = <span class="dt">String</span>::new();
<span class="kw">for</span> c <span class="kw">in</span> name.chars() {
<span class="kw">match</span> c {
<span class="ch">'a'</span> | <span class="ch">'e'</span> | <span class="ch">'i'</span> | <span class="ch">'o'</span> | <span class="ch">'u'</span> => {
<span class="co">// skip vowels</span>
}
_ => {
output.push(c);
}
}
}
output
}
<span class="kw">fn</span> print_out(name: <span class="dt">String</span>) {
<span class="kw">let</span> devowelized_name = remove_vowels(name);
<span class="pp">println!</span>(<span class="st">"Removing vowels yields {:?}"</span>, devowelized_name);
<span class="co">// Goal #2: What happens when you uncomment the following</span>
<span class="co">// line? Can you change the code above so that this next line?</span>
<span class="co">// println!("Removing vowels from {:?} yields {:?}",</span>
<span class="co">// name, devowelized_name);</span>
<span class="co">// Extra credit: Can you do it without copying any data?</span>
<span class="co">// (Using only ownership transfer)</span>
}</code></pre></div>
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