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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
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+                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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+            Jun 28, 2023
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+    <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&#x2F;reset, control&#x2F;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> -&gt;</span><br><span class="line">               <span class="number">1</span>::<span class="number">2</span>::take_subcont p (<span class="keyword">fun</span> _k -&gt; <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> -&gt;</span><br><span class="line">               <span class="number">1</span>::<span class="number">2</span>::take_subcont p (<span class="keyword">fun</span> k -&gt; 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> -&gt;</span><br><span class="line">      sk (<span class="keyword">fun</span> <span class="literal">()</span> -&gt;</span><br><span class="line">        shift0 p2 (<span class="keyword">fun</span> sk2 -&gt; sk2 (<span class="keyword">fun</span> <span class="literal">()</span> -&gt;</span><br><span class="line">          sk2 (<span class="keyword">fun</span> <span class="literal">()</span> -&gt; <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> -&gt;</span><br><span class="line">     push_prompt p2 (<span class="keyword">fun</span> <span class="literal">()</span> -&gt;</span><br><span class="line">       push_prompt p3 (<span class="keyword">fun</span> <span class="literal">()</span> -&gt; 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">&quot;Success!&quot;</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&#x27; 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&#x27; interprets `Twice&#x27; 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">  = &#123; retc = (<span class="keyword">fun</span> x -&gt; x)</span><br><span class="line">    ; exnc = (<span class="keyword">fun</span> e -&gt; 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) -&gt;</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> -&gt; <span class="type">Some</span> (<span class="keyword">fun</span> (k : (a, _) continuation) -&gt;</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">      | _ -&gt; <span class="type">None</span>) &#125;</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&#x27; 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&#x27;, hence the optimiser will transform</span></span><br><span class="line"><span class="comment">   `i&#x27; 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)&#x27; will succeed twice, whereas</span></span><br><span class="line"><span class="comment">   it should fail after the second return of `perform Twice&#x27;. *)</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> -&gt;</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">&quot;i = %d\n%!&quot;</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&#x27;. 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&#x27; <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> -&gt;</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">&quot;i = %d\n%!&quot;</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&#x27; <span class="literal">()</span></span><br></pre></td></tr></table></figure>
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