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# 减少runtime check
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## 减少集合访问的边界检查
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以下代码，我们实现了两种循环方式：
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```rust
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// 第一种
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let collection = [1, 2, 3, 4, 5];
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for i in 0..collection.len() {
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let item = collection[i];
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// ...
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}
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// 第二种
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for item in collection {
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}
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```
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第一种方式是循环索引，然后通过索引下标去访问集合，第二种方式是直接循环迭代集合中的元素，优劣如下：
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- **性能**：第一种使用方式中`collection[index]`的索引访问，会因为边界检查(bounds checking)导致运行时的性能损耗 - Rust会检查并确认`index`是落在集合内也就是合法的，但是第二种直接迭代的方式就不会触发这种检查,因为编译器会在编译时就完成分析并证明这种访问是合法的`
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## Box::leak
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https://www.reddit.com/r/rust/comments/rntx7s/why_use_boxleak/
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## bounds check
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https://www.reddit.com/r/rust/comments/rnbubh/whats_the_big_deal_with_bounds_checking/
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https://www.reddit.com/r/rust/comments/s6u65e/optimization_of_bubble_sort_fails_without_hinting/
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## 使用assert 优化检查性能
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https://www.reddit.com/r/rust/comments/rui1zz/write_assertions_that_clarify_code_to_both_the/
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