ed5015939f
Implement .zip() specialization for Map and Cloned. The crucial thing for transparent specialization is that we want to preserve the potential side effects. The simplest example is that in this code snippet: `(0..6).map(f).zip((0..4).map(g)).count()` `f` will be called five times, and `g` four times. The last time for `f` is when the other iterator is at its end, so this element is unused. This side effect can be preserved without disturbing code generation for simple uses of `.map()`. The `Zip::next_back()` case is even more complicated, unfortunately.
29 lines
1.1 KiB
Rust
29 lines
1.1 KiB
Rust
// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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/// An iterator whose items are random accessible efficiently
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///
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/// # Safety
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///
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/// The iterator's .len() and size_hint() must be exact.
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/// `.len()` must be cheap to call.
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///
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/// .get_unchecked() must return distinct mutable references for distinct
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/// indices (if applicable), and must return a valid reference if index is in
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/// 0..self.len().
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#[doc(hidden)]
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pub unsafe trait TrustedRandomAccess : ExactSizeIterator {
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unsafe fn get_unchecked(&mut self, i: usize) -> Self::Item;
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/// Return `true` if getting an iterator element may have
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/// side effects. Remember to take inner iterators into account.
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fn may_have_side_effect() -> bool;
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}
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