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</pre><pre class="rust ">
<span class="kw">use</span> <span class="ident">core</span>::<span class="ident">ops</span>::{<span class="ident">Add</span>, <span class="ident">Mul</span>};
<span class="kw">use</span> <span class="ident">core</span>::<span class="ident">num</span>::<span class="ident">Wrapping</span>;
<span class="doccomment">/// Defines an additive identity element for `Self`.</span>
<span class="kw">pub</span> <span class="kw">trait</span> <span class="ident">Zero</span>: <span class="ident">Sized</span> <span class="op">+</span> <span class="ident">Add</span><span class="op"><</span><span class="self">Self</span>, <span class="ident">Output</span> <span class="op">=</span> <span class="self">Self</span><span class="op">></span> {
<span class="doccomment">/// Returns the additive identity element of `Self`, `0`.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Laws</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```{.text}</span>
<span class="doccomment">/// a + 0 = a ∀ a ∈ Self</span>
<span class="doccomment">/// 0 + a = a ∀ a ∈ Self</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Purity</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This function should return the same result at all times regardless of</span>
<span class="doccomment">/// external mutable state, for example values stored in TLS or in</span>
<span class="doccomment">/// `static mut`s.</span>
<span class="comment">// FIXME (#5527): This should be an associated constant</span>
<span class="kw">fn</span> <span class="ident">zero</span>() <span class="op">-></span> <span class="self">Self</span>;
<span class="doccomment">/// Returns `true` if `self` is equal to the additive identity.</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">is_zero</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-></span> <span class="ident">bool</span>;
}
<span class="macro">macro_rules</span><span class="macro">!</span> <span class="ident">zero_impl</span> {
(<span class="macro-nonterminal">$</span><span class="macro-nonterminal">t</span>:<span class="ident">ty</span>, <span class="macro-nonterminal">$</span><span class="macro-nonterminal">v</span>:<span class="ident">expr</span>) <span class="op">=></span> {
<span class="kw">impl</span> <span class="ident">Zero</span> <span class="kw">for</span> <span class="macro-nonterminal">$</span><span class="macro-nonterminal">t</span> {
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">zero</span>() <span class="op">-></span> <span class="macro-nonterminal">$</span><span class="macro-nonterminal">t</span> { <span class="macro-nonterminal">$</span><span class="macro-nonterminal">v</span> }
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">is_zero</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-></span> <span class="ident">bool</span> { <span class="kw-2">*</span><span class="self">self</span> <span class="op">==</span> <span class="macro-nonterminal">$</span><span class="macro-nonterminal">v</span> }
}
}
}
<span class="macro">zero_impl</span><span class="macro">!</span>(<span class="ident">usize</span>, <span class="number">0usize</span>);
<span class="macro">zero_impl</span><span class="macro">!</span>(<span class="ident">u8</span>, <span class="number">0u8</span>);
<span class="macro">zero_impl</span><span class="macro">!</span>(<span class="ident">u16</span>, <span class="number">0u16</span>);
<span class="macro">zero_impl</span><span class="macro">!</span>(<span class="ident">u32</span>, <span class="number">0u32</span>);
<span class="macro">zero_impl</span><span class="macro">!</span>(<span class="ident">u64</span>, <span class="number">0u64</span>);
<span class="macro">zero_impl</span><span class="macro">!</span>(<span class="ident">isize</span>, <span class="number">0isize</span>);
<span class="macro">zero_impl</span><span class="macro">!</span>(<span class="ident">i8</span>, <span class="number">0i8</span>);
<span class="macro">zero_impl</span><span class="macro">!</span>(<span class="ident">i16</span>, <span class="number">0i16</span>);
<span class="macro">zero_impl</span><span class="macro">!</span>(<span class="ident">i32</span>, <span class="number">0i32</span>);
<span class="macro">zero_impl</span><span class="macro">!</span>(<span class="ident">i64</span>, <span class="number">0i64</span>);
<span class="macro">zero_impl</span><span class="macro">!</span>(<span class="ident">f32</span>, <span class="number">0.0f32</span>);
<span class="macro">zero_impl</span><span class="macro">!</span>(<span class="ident">f64</span>, <span class="number">0.0f64</span>);
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span>: <span class="ident">Zero</span><span class="op">></span> <span class="ident">Zero</span> <span class="kw">for</span> <span class="ident">Wrapping</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> <span class="kw">where</span> <span class="ident">Wrapping</span><span class="op"><</span><span class="ident">T</span><span class="op">></span>: <span class="ident">Add</span><span class="op"><</span><span class="ident">Output</span><span class="op">=</span><span class="ident">Wrapping</span><span class="op"><</span><span class="ident">T</span><span class="op">>></span> {
<span class="kw">fn</span> <span class="ident">is_zero</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-></span> <span class="ident">bool</span> {
<span class="self">self</span>.<span class="number">0</span>.<span class="ident">is_zero</span>()
}
<span class="kw">fn</span> <span class="ident">zero</span>() <span class="op">-></span> <span class="self">Self</span> {
<span class="ident">Wrapping</span>(<span class="ident">T</span>::<span class="ident">zero</span>())
}
}
<span class="doccomment">/// Defines a multiplicative identity element for `Self`.</span>
<span class="kw">pub</span> <span class="kw">trait</span> <span class="ident">One</span>: <span class="ident">Sized</span> <span class="op">+</span> <span class="ident">Mul</span><span class="op"><</span><span class="self">Self</span>, <span class="ident">Output</span> <span class="op">=</span> <span class="self">Self</span><span class="op">></span> {
<span class="doccomment">/// Returns the multiplicative identity element of `Self`, `1`.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Laws</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```{.text}</span>
<span class="doccomment">/// a * 1 = a ∀ a ∈ Self</span>
<span class="doccomment">/// 1 * a = a ∀ a ∈ Self</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Purity</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This function should return the same result at all times regardless of</span>
<span class="doccomment">/// external mutable state, for example values stored in TLS or in</span>
<span class="doccomment">/// `static mut`s.</span>
<span class="comment">// FIXME (#5527): This should be an associated constant</span>
<span class="kw">fn</span> <span class="ident">one</span>() <span class="op">-></span> <span class="self">Self</span>;
<span class="doccomment">/// Returns `true` if `self` is equal to the multiplicative identity.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// For performance reasons, it's best to implement this manually.</span>
<span class="doccomment">/// After a semver bump, this method will be required, and the</span>
<span class="doccomment">/// `where Self: PartialEq` bound will be removed.</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">is_one</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-></span> <span class="ident">bool</span> <span class="kw">where</span> <span class="self">Self</span>: <span class="ident">PartialEq</span> {
<span class="kw-2">*</span><span class="self">self</span> <span class="op">==</span> <span class="self">Self</span>::<span class="ident">one</span>()
}
}
<span class="macro">macro_rules</span><span class="macro">!</span> <span class="ident">one_impl</span> {
(<span class="macro-nonterminal">$</span><span class="macro-nonterminal">t</span>:<span class="ident">ty</span>, <span class="macro-nonterminal">$</span><span class="macro-nonterminal">v</span>:<span class="ident">expr</span>) <span class="op">=></span> {
<span class="kw">impl</span> <span class="ident">One</span> <span class="kw">for</span> <span class="macro-nonterminal">$</span><span class="macro-nonterminal">t</span> {
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">one</span>() <span class="op">-></span> <span class="macro-nonterminal">$</span><span class="macro-nonterminal">t</span> { <span class="macro-nonterminal">$</span><span class="macro-nonterminal">v</span> }
}
}
}
<span class="macro">one_impl</span><span class="macro">!</span>(<span class="ident">usize</span>, <span class="number">1usize</span>);
<span class="macro">one_impl</span><span class="macro">!</span>(<span class="ident">u8</span>, <span class="number">1u8</span>);
<span class="macro">one_impl</span><span class="macro">!</span>(<span class="ident">u16</span>, <span class="number">1u16</span>);
<span class="macro">one_impl</span><span class="macro">!</span>(<span class="ident">u32</span>, <span class="number">1u32</span>);
<span class="macro">one_impl</span><span class="macro">!</span>(<span class="ident">u64</span>, <span class="number">1u64</span>);
<span class="macro">one_impl</span><span class="macro">!</span>(<span class="ident">isize</span>, <span class="number">1isize</span>);
<span class="macro">one_impl</span><span class="macro">!</span>(<span class="ident">i8</span>, <span class="number">1i8</span>);
<span class="macro">one_impl</span><span class="macro">!</span>(<span class="ident">i16</span>, <span class="number">1i16</span>);
<span class="macro">one_impl</span><span class="macro">!</span>(<span class="ident">i32</span>, <span class="number">1i32</span>);
<span class="macro">one_impl</span><span class="macro">!</span>(<span class="ident">i64</span>, <span class="number">1i64</span>);
<span class="macro">one_impl</span><span class="macro">!</span>(<span class="ident">f32</span>, <span class="number">1.0f32</span>);
<span class="macro">one_impl</span><span class="macro">!</span>(<span class="ident">f64</span>, <span class="number">1.0f64</span>);
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span>: <span class="ident">One</span><span class="op">></span> <span class="ident">One</span> <span class="kw">for</span> <span class="ident">Wrapping</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> <span class="kw">where</span> <span class="ident">Wrapping</span><span class="op"><</span><span class="ident">T</span><span class="op">></span>: <span class="ident">Mul</span><span class="op"><</span><span class="ident">Output</span><span class="op">=</span><span class="ident">Wrapping</span><span class="op"><</span><span class="ident">T</span><span class="op">>></span> {
<span class="kw">fn</span> <span class="ident">one</span>() <span class="op">-></span> <span class="self">Self</span> {
<span class="ident">Wrapping</span>(<span class="ident">T</span>::<span class="ident">one</span>())
}
}
<span class="comment">// Some helper functions provided for backwards compatibility.</span>
<span class="doccomment">/// Returns the additive identity, `0`.</span>
<span class="attribute">#[<span class="ident">inline</span>(<span class="ident">always</span>)]</span> <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">zero</span><span class="op"><</span><span class="ident">T</span>: <span class="ident">Zero</span><span class="op">></span>() <span class="op">-></span> <span class="ident">T</span> { <span class="ident">Zero</span>::<span class="ident">zero</span>() }
<span class="doccomment">/// Returns the multiplicative identity, `1`.</span>
<span class="attribute">#[<span class="ident">inline</span>(<span class="ident">always</span>)]</span> <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">one</span><span class="op"><</span><span class="ident">T</span>: <span class="ident">One</span><span class="op">></span>() <span class="op">-></span> <span class="ident">T</span> { <span class="ident">One</span>::<span class="ident">one</span>() }
<span class="attribute">#[<span class="ident">test</span>]</span>
<span class="kw">fn</span> <span class="ident">wrapping_identities</span>() {
<span class="macro">macro_rules</span><span class="macro">!</span> <span class="ident">test_wrapping_identities</span> {
($(<span class="macro-nonterminal">$</span><span class="macro-nonterminal">t</span>:<span class="ident">ty</span>)<span class="op">+</span>) <span class="op">=></span> {
$(
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">zero</span>::<span class="op"><</span><span class="macro-nonterminal">$</span><span class="macro-nonterminal">t</span><span class="op">></span>(), <span class="ident">zero</span>::<span class="op"><</span><span class="ident">Wrapping</span><span class="op"><</span><span class="macro-nonterminal">$</span><span class="macro-nonterminal">t</span><span class="op">>></span>().<span class="number">0</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">one</span>::<span class="op"><</span><span class="macro-nonterminal">$</span><span class="macro-nonterminal">t</span><span class="op">></span>(), <span class="ident">one</span>::<span class="op"><</span><span class="ident">Wrapping</span><span class="op"><</span><span class="macro-nonterminal">$</span><span class="macro-nonterminal">t</span><span class="op">>></span>().<span class="number">0</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>((<span class="number">0</span> <span class="kw">as</span> <span class="macro-nonterminal">$</span><span class="macro-nonterminal">t</span>).<span class="ident">is_zero</span>(), <span class="ident">Wrapping</span>(<span class="number">0</span> <span class="kw">as</span> <span class="macro-nonterminal">$</span><span class="macro-nonterminal">t</span>).<span class="ident">is_zero</span>());
<span class="macro">assert_eq</span><span class="macro">!</span>((<span class="number">1</span> <span class="kw">as</span> <span class="macro-nonterminal">$</span><span class="macro-nonterminal">t</span>).<span class="ident">is_zero</span>(), <span class="ident">Wrapping</span>(<span class="number">1</span> <span class="kw">as</span> <span class="macro-nonterminal">$</span><span class="macro-nonterminal">t</span>).<span class="ident">is_zero</span>());
)<span class="op">+</span>
};
}
<span class="macro">test_wrapping_identities</span><span class="macro">!</span>(<span class="ident">isize</span> <span class="ident">i8</span> <span class="ident">i16</span> <span class="ident">i32</span> <span class="ident">i64</span> <span class="ident">usize</span> <span class="ident">u8</span> <span class="ident">u16</span> <span class="ident">u32</span> <span class="ident">u64</span>);
}
<span class="attribute">#[<span class="ident">test</span>]</span>
<span class="kw">fn</span> <span class="ident">wrapping_is_zero</span>() {
<span class="kw">fn</span> <span class="ident">require_zero</span><span class="op"><</span><span class="ident">T</span>: <span class="ident">Zero</span><span class="op">></span>(_: <span class="kw-2">&</span><span class="ident">T</span>) {}
<span class="ident">require_zero</span>(<span class="kw-2">&</span><span class="ident">Wrapping</span>(<span class="number">42</span>));
}
<span class="attribute">#[<span class="ident">test</span>]</span>
<span class="kw">fn</span> <span class="ident">wrapping_is_one</span>() {
<span class="kw">fn</span> <span class="ident">require_one</span><span class="op"><</span><span class="ident">T</span>: <span class="ident">One</span><span class="op">></span>(_: <span class="kw-2">&</span><span class="ident">T</span>) {}
<span class="ident">require_one</span>(<span class="kw-2">&</span><span class="ident">Wrapping</span>(<span class="number">42</span>));
}
</pre>
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Prefix searches with a type followed by a colon (e.g.
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Accepted types are: <code>fn</code>, <code>mod</code>,
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<code>trait</code>, <code>type</code>, <code>macro</code>,
and <code>const</code>.
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Search functions by type signature (e.g.
<code>vec -> usize</code> or <code>* -> vec</code>)
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