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Diffstat (limited to '2023/06/28/隐藏一些OCaml-Effect的机制，让其语法在精神上更接近delimcc')
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diff --git a/2023/06/28/隐藏一些OCaml-Effect的机制，让其语法在精神上更接近delimcc/index.html b/2023/06/28/隐藏一些OCaml-Effect的机制，让其语法在精神上更接近delimcc/index.html new file mode 100644 index 00000000..cc6471c9 --- /dev/null +++ b/2023/06/28/隐藏一些OCaml-Effect的机制，让其语法在精神上更接近delimcc/index.html @@ -0,0 +1,237 @@ +<!DOCTYPE html> +<html lang="en"> + <head> + <meta charset="UTF-8"> +<meta name="viewport" + content="width=device-width, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0"> +<meta http-equiv="X-UA-Compatible" content="ie=edge"> + + <meta name="author" content="含暮秋"> + + + <meta name="subtitle" content="暮秋小屋"> + + + <meta name="description" content="不卑不亢的码农， 朴素的民谣诗人"> + + + <meta name="keywords" content="韩暮秋,MuqiuHan"> + + + + +<title>隐藏一些OCaml Effect的机制，让其语法在精神上更接近delimcc | 暮秋小屋</title> + + + + + +<style> + @import url('https://fonts.googleapis.com/css2?family=Inter:wght@300;400;500;600;700&family=Noto+Sans+SC:wght@300;400;500;700&family=Roboto+Mono&display=swap'); +</style> + + + + <!-- stylesheets 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<div class="h-line-primary"></div> + + </div> +</div> + <div class="post-content"> + <p><a target="_blank" rel="noopener" href="https://github.com/kayceesrk/delimcc_of_fxhandler">delimcc_of_fxhandler这个库</a>在OCaml5的effect handlers上实现了一些delimcc原语(shift/reset, control/prompt这些)：</p> +<figure class="highlight ocaml"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">let</span> p = new_prompt <span class="literal">()</span> <span class="keyword">in</span></span><br><span class="line"><span class="keyword">assert</span> (<span class="literal">[]</span> = push_prompt p (<span class="keyword">fun</span> <span class="literal">()</span> -></span><br><span class="line"> <span class="number">1</span>::<span class="number">2</span>::take_subcont p (<span class="keyword">fun</span> _k -> <span class="literal">[]</span>)));</span><br><span class="line"><span class="keyword">assert</span> ([<span class="number">1</span>;<span class="number">2</span>] = push_prompt p (<span class="keyword">fun</span> <span class="literal">()</span> -></span><br><span class="line"> <span class="number">1</span>::<span class="number">2</span>::take_subcont p (<span class="keyword">fun</span> k -> push_subcont k <span class="literal">[]</span>)));</span><br><span class="line"><span class="keyword">assert</span> (<span class="number">135</span> =</span><br><span class="line"> <span class="keyword">let</span> p1 = new_prompt <span class="literal">()</span> <span class="keyword">in</span></span><br><span class="line"> <span class="keyword">let</span> p2 = new_prompt <span class="literal">()</span> <span class="keyword">in</span></span><br><span class="line"> <span class="keyword">let</span> p3 = new_prompt <span class="literal">()</span> <span class="keyword">in</span></span><br><span class="line"> <span class="keyword">let</span> pushtwice sk =</span><br><span class="line"> sk (<span class="keyword">fun</span> <span class="literal">()</span> -></span><br><span class="line"> sk (<span class="keyword">fun</span> <span class="literal">()</span> -></span><br><span class="line"> shift0 p2 (<span class="keyword">fun</span> sk2 -> sk2 (<span class="keyword">fun</span> <span class="literal">()</span> -></span><br><span class="line"> sk2 (<span class="keyword">fun</span> <span class="literal">()</span> -> <span class="number">3</span>))) <span class="literal">()</span>))</span><br><span class="line"> <span class="keyword">in</span></span><br><span class="line"> push_prompt p1 (<span class="keyword">fun</span> <span class="literal">()</span> -></span><br><span class="line"> push_prompt p2 (<span class="keyword">fun</span> <span class="literal">()</span> -></span><br><span class="line"> push_prompt p3 (<span class="keyword">fun</span> <span class="literal">()</span> -> shift0 p1 pushtwice <span class="literal">()</span>) + <span class="number">10</span>) + <span class="number">1</span>) + <span class="number">100</span>);</span><br><span class="line"></span><br><span class="line">print_endline <span class="string">"Success!"</span></span><br></pre></td></tr></table></figure> + +<p>另外， <a target="_blank" rel="noopener" href="https://github.com/avsm/ocaml/commits/effect-syntax">avsm这里</a>可以看到一些OCaml的Effect Syntax进展。</p> +<p>还有 <a target="_blank" rel="noopener" href="https://github.com/dhil/ocaml-multicont">multi-shot continuations in OCaml</a>，在这个仓库里面还讨论了一些有趣的问题，例如，OCaml 编译器和runtime会做出一些假设从而进行一些优化，这些优化在使用multi-shot continutation时是不可取的（或完全错误的）。编译器优化导致错误的一个例子是堆到栈的转换，例如:</p> +<figure class="highlight ocaml"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br><span class="line">56</span><br><span class="line">57</span><br><span class="line">58</span><br><span class="line">59</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">(* An illustration of how the heap to stack optimisation is broken.</span></span><br><span class="line"><span class="comment"> * This example is adapted from de Vilhena and Pottier (2021).</span></span><br><span class="line"><span class="comment"> * file: heap2stack.ml</span></span><br><span class="line"><span class="comment"> * compile: ocamlopt -I $(opam var lib)/multicont multicont.cmxa heap2stack.ml</span></span><br><span class="line"><span class="comment"> * run: ./a.out *)</span></span><br><span class="line"></span><br><span class="line"><span class="comment">(* We first require a little bit of setup. The following declares an</span></span><br><span class="line"><span class="comment"> operation `Twice' which we use to implement multiple returns. *)</span></span><br><span class="line"><span class="keyword">type</span> _ <span class="type">Effect</span>.t += <span class="type">Twice</span> : <span class="built_in">unit</span> <span class="type">Effect</span>.t</span><br><span class="line"></span><br><span class="line"><span class="comment">(* The handler `htwice' interprets `Twice' by simply invoking its</span></span><br><span class="line"><span class="comment"> continuation twice. *)</span></span><br><span class="line"><span class="keyword">let</span> htwice : (<span class="built_in">unit</span>, <span class="built_in">unit</span>) <span class="type">Effect</span>.<span class="type">Deep</span>.handler</span><br><span class="line"> = { retc = (<span class="keyword">fun</span> x -> x)</span><br><span class="line"> ; exnc = (<span class="keyword">fun</span> e -> raise e)</span><br><span class="line"> ; effc = (<span class="keyword">fun</span> (<span class="keyword">type</span> a) (eff : a <span class="type">Effect</span>.t) -></span><br><span class="line"> <span class="keyword">let</span> <span class="keyword">open</span> <span class="type">Effect</span>.<span class="type">Deep</span> <span class="keyword">in</span></span><br><span class="line"> <span class="keyword">match</span> eff <span class="keyword">with</span></span><br><span class="line"> | <span class="type">Twice</span> -> <span class="type">Some</span> (<span class="keyword">fun</span> (k : (a, _) continuation) -></span><br><span class="line"> continue (<span class="type">Multicont</span>.<span class="type">Deep</span>.clone_continuation k) <span class="literal">()</span>;</span><br><span class="line"> continue k <span class="literal">()</span>)</span><br><span class="line"> | _ -> <span class="type">None</span>) }</span><br><span class="line"></span><br><span class="line"><span class="comment">(* Now for the interesting stuff. In the code below, the compiler will</span></span><br><span class="line"><span class="comment"> perform an escape analysis on the reference `i' and deduce that it</span></span><br><span class="line"><span class="comment"> does not escape the local scope, because it is unaware of the</span></span><br><span class="line"><span class="comment"> semantics of `perform Twice', hence the optimiser will transform</span></span><br><span class="line"><span class="comment"> `i' into an immediate on the stack to save a heap allocation. As a</span></span><br><span class="line"><span class="comment"> consequence, the assertion `(!i = 1)' will succeed twice, whereas</span></span><br><span class="line"><span class="comment"> it should fail after the second return of `perform Twice'. *)</span></span><br><span class="line"><span class="keyword">let</span> heap2stack <span class="literal">()</span> =</span><br><span class="line"> <span class="type">Effect</span>.<span class="type">Deep</span>.match_with</span><br><span class="line"> (<span class="keyword">fun</span> <span class="literal">()</span> -></span><br><span class="line"> <span class="keyword">let</span> i = <span class="built_in">ref</span> <span class="number">0</span> <span class="keyword">in</span></span><br><span class="line"> <span class="type">Effect</span>.perform <span class="type">Twice</span>;</span><br><span class="line"> i := !i + <span class="number">1</span>;</span><br><span class="line"> <span class="type">Printf</span>.printf <span class="string">"i = %d\n%!"</span> !i;</span><br><span class="line"> <span class="keyword">assert</span> (!i = <span class="number">1</span>))</span><br><span class="line"> <span class="literal">()</span> htwice</span><br><span class="line"></span><br><span class="line"><span class="comment">(* The following does not trigger an assertion failure. *)</span></span><br><span class="line"><span class="keyword">let</span> _ = heap2stack <span class="literal">()</span></span><br><span class="line"></span><br><span class="line"><span class="comment">(* To fix this issue, we can wrap reference allocations in an instance</span></span><br><span class="line"><span class="comment"> of `Sys.opaque_identity'. However, this is not really a viable fix</span></span><br><span class="line"><span class="comment"> in general, as we may not have access to the client code that</span></span><br><span class="line"><span class="comment"> allocates the reference! *)</span></span><br><span class="line"><span class="keyword">let</span> heap2stack' <span class="literal">()</span> =</span><br><span class="line"> <span class="type">Effect</span>.<span class="type">Deep</span>.match_with</span><br><span class="line"> (<span class="keyword">fun</span> <span class="literal">()</span> -></span><br><span class="line"> <span class="keyword">let</span> i = <span class="type">Sys</span>.opaque_identity (<span class="built_in">ref</span> <span class="number">0</span>) <span class="keyword">in</span></span><br><span class="line"> <span class="type">Effect</span>.perform <span class="type">Twice</span>;</span><br><span class="line"> i := !i + <span class="number">1</span>;</span><br><span class="line"> <span class="type">Printf</span>.printf <span class="string">"i = %d\n%!"</span> !i;</span><br><span class="line"> <span class="keyword">assert</span> (!i = <span class="number">1</span>))</span><br><span class="line"> <span class="literal">()</span> htwice</span><br><span class="line"></span><br><span class="line"><span class="comment">(* The following triggers an assertion failure. *)</span></span><br><span class="line"><span class="keyword">let</span> _ = heap2stack' <span class="literal">()</span></span><br></pre></td></tr></table></figure> + +</div> + +<script> + window.onload = detectors(); +</script> + <div class="post-footer"> + <div class="h-line-primary"></div> + <nav class="post-nav"> + <div class="prev-item"> + + <div class="icon arrow-left"></div> + <div class="post-link"> + <a href="/2023/06/28/OOP-Visitors%E5%9C%A8Polymorphic%E6%83%85%E5%86%B5%E4%B8%8B%E7%9A%84%E7%B1%BB%E5%9E%8B%E9%94%99%E8%AF%AF/">Prev</a> + </div> + + </div> + <div class="next-item"> + + <div class="icon arrow-right"></div> + <div class="post-link"> + <a href="/2023/06/28/caml-release-runtime-system%E5%AF%BC%E8%87%B4%E7%9A%84%E6%AD%BB%E9%94%81%E9%97%AE%E9%A2%98/">Next</a> + </div> + + </div> + </nav> +</div> + + + <div class="post-comment"> + + + + + + + +</div> + + +</article> + </div> + </div> + + <div class="footer"> + <div class="flex-container"> + <div class="footer-text"> + + + | + + + 希望路过的人可以添点柴火让这里暖和点 + + </div> + </div> +</div> + + </div> + + + + + </body> +</html> |