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<h1 class='fqn'><span class='in-band'>Function <a href='../index.html'>futures</a>::<wbr><a href='index.html'>future</a>::<wbr><a class="fn" href=''>lazy</a></span><span class='out-of-band'><span id='render-detail'>
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               </span><a class='srclink' href='../../src/futures/future/lazy.rs.html#44-51' title='goto source code'>[src]</a></span></h1>
<pre class='rust fn'>pub fn lazy&lt;F, R&gt;(f: F) -&gt; <a class="struct" href="../../futures/future/struct.Lazy.html" title="struct futures::future::Lazy">Lazy</a>&lt;F, R&gt; <span class="where fmt-newline">where<br>&nbsp;&nbsp;&nbsp;&nbsp;F: <a class="trait" href="https://doc.rust-lang.org/nightly/core/ops/function/trait.FnOnce.html" title="trait core::ops::function::FnOnce">FnOnce</a>() -&gt; R,<br>&nbsp;&nbsp;&nbsp;&nbsp;R: <a class="trait" href="../../futures/future/trait.IntoFuture.html" title="trait futures::future::IntoFuture">IntoFuture</a>,&nbsp;</span></pre><div class='docblock'><p>Creates a new future which will eventually be the same as the one created
by the closure provided.</p>
<p>The provided closure is only run once the future has a callback scheduled
on it, otherwise the callback never runs. Once run, however, this future is
the same as the one the closure creates.</p>
<h1 id="examples" class="section-header"><a href="#examples">Examples</a></h1>
<pre class="rust rust-example-rendered">
<span class="kw">use</span> <span class="ident">futures</span>::<span class="ident">future</span>::<span class="kw-2">*</span>;

<span class="kw">let</span> <span class="ident">a</span> <span class="op">=</span> <span class="ident">lazy</span>(<span class="op">||</span> <span class="ident">ok</span>::<span class="op">&lt;</span><span class="ident">u32</span>, <span class="ident">u32</span><span class="op">&gt;</span>(<span class="number">1</span>));

<span class="kw">let</span> <span class="ident">b</span> <span class="op">=</span> <span class="ident">lazy</span>(<span class="op">||</span> <span class="op">-&gt;</span> <span class="ident">FutureResult</span><span class="op">&lt;</span><span class="ident">u32</span>, <span class="ident">u32</span><span class="op">&gt;</span> {
    <span class="macro">panic</span><span class="macro">!</span>(<span class="string">&quot;oh no!&quot;</span>)
});
<span class="ident">drop</span>(<span class="ident">b</span>); <span class="comment">// closure is never run</span></pre>
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