diff options
Diffstat (limited to '2023')
| -rw-r--r-- | 2023/06/28/OOP-Visitors在Polymorphic情况下的类型错误/index.html | 242 | ||||
| -rw-r--r-- | 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 | 2 | ||||
| -rw-r--r-- | 2023/06/29/二〇二三年六月二十九日/index.html | 2 |
3 files changed, 2 insertions, 244 deletions
diff --git a/2023/06/28/OOP-Visitors在Polymorphic情况下的类型错误/index.html b/2023/06/28/OOP-Visitors在Polymorphic情况下的类型错误/index.html deleted file mode 100644 index 5dcff3a0..00000000 --- a/2023/06/28/OOP-Visitors在Polymorphic情况下的类型错误/index.html +++ /dev/null @@ -1,242 +0,0 @@ -<!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="韩暮秋"> - - - <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>OOP Visitors在Polymorphic情况下的类型错误 | 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 list from _config.yml --> - 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-<p>要是从字面上直接翻译成OCaml:</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></pre></td><td class="code"><pre><span class="line"><span class="keyword">class</span> <span class="keyword">virtual</span> tree =</span><br><span class="line"> <span class="keyword">object</span></span><br><span class="line"> <span class="keyword">method</span> <span class="keyword">virtual</span> accept : <span class="symbol">'a</span> . <span class="symbol">'a</span> tree_visitor -> <span class="symbol">'a</span></span><br><span class="line"> <span class="keyword">end</span></span><br><span class="line"></span><br><span class="line"><span class="keyword">and</span> <span class="keyword">virtual</span> [<span class="symbol">'a</span>] tree_visitor =</span><br><span class="line"> <span class="keyword">object</span></span><br><span class="line"> <span class="keyword">method</span> <span class="keyword">virtual</span> visit_leaf : (leaf -> <span class="symbol">'a</span>)</span><br><span class="line"> <span class="keyword">end</span></span><br><span class="line"></span><br><span class="line"><span class="keyword">and</span> leaf (i : <span class="built_in">int</span>) =</span><br><span class="line"> <span class="keyword">object</span> (self)</span><br><span class="line"> <span class="keyword">method</span> get = i</span><br><span class="line"></span><br><span class="line"> <span class="keyword">method</span> accept (v : <span class="symbol">'a</span> tree_visitor) : <span class="symbol">'a</span> =</span><br><span class="line"> v#visit_leaf (self :> leaf)</span><br><span class="line"> <span class="keyword">end</span></span><br></pre></td></tr></table></figure> - -<p>是行不通滴:</p> -<figure class="highlight plaintext"><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></pre></td><td class="code"><pre><span class="line">File "visitor.ml", line 3, characters 28-54:</span><br><span class="line">3 | method virtual accept : 'a . 'a tree_visitor -> 'a</span><br><span class="line"> ^^^^^^^^^^^^^^^^^^^^^^^^^^</span><br><span class="line">Error: The universal type variable 'a cannot be generalized:</span><br><span class="line"> it escapes its scope.</span><br></pre></td></tr></table></figure> - -<p>OCaml的类在定义时是单态的，比如:</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></pre></td><td class="code"><pre><span class="line"><span class="keyword">class</span> [<span class="symbol">'a</span>] c (x:<span class="symbol">'a</span>) = </span><br><span class="line"> <span class="keyword">object</span></span><br><span class="line"> <span class="keyword">method</span> x = x</span><br><span class="line"> <span class="keyword">end</span></span><br><span class="line"><span class="keyword">and</span> d = </span><br><span class="line"> <span class="keyword">object</span></span><br><span class="line"> <span class="keyword">method</span> strange = (<span class="keyword">new</span> c <span class="number">0</span>)#x</span><br><span class="line"> <span class="keyword">end</span></span><br></pre></td></tr></table></figure> - -<p>这里c是:</p> -<figure class="highlight ocaml"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">class</span> [<span class="symbol">'a</span>] c : <span class="symbol">'a</span> -> <span class="keyword">object</span> <span class="keyword">constraint</span> <span class="symbol">'a</span> = <span class="built_in">int</span> <span class="keyword">method</span> x : <span class="symbol">'a</span> <span class="keyword">end</span></span><br></pre></td></tr></table></figure> - -<p>因为在d里面<code>new c 0</code>了一个 <code>int c</code> 的对象。</p> -<p>所以正确的写法应该是:</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></pre></td><td class="code"><pre><span class="line"><span class="keyword">class</span> <span class="keyword">virtual</span> [<span class="symbol">'a</span>, <span class="symbol">'leaf</span>, <span class="symbol">'node</span>, <span class="symbol">'empty</span>] open_tree_visitor = </span><br><span class="line"> <span class="keyword">object</span></span><br><span class="line"> <span class="keyword">method</span> <span class="keyword">virtual</span> visit_leaf : <span class="symbol">'leaf</span> -> <span class="symbol">'a</span></span><br><span class="line"> <span class="keyword">method</span> <span class="keyword">virtual</span> visit_node : <span class="symbol">'node</span> -> <span class="symbol">'a</span></span><br><span class="line"> <span class="keyword">method</span> <span class="keyword">virtual</span> visit_empty : <span class="symbol">'empty</span> -> <span class="symbol">'a</span></span><br><span class="line"> <span class="keyword">end</span></span><br><span class="line"></span><br><span class="line"><span class="keyword">class</span> <span class="keyword">virtual</span> tree = </span><br><span class="line"> <span class="keyword">object</span></span><br><span class="line"> <span class="keyword">method</span> <span class="keyword">virtual</span> accept : <span class="symbol">'a</span> .</span><br><span class="line"> (<span class="symbol">'a</span>, <span class="symbol">'leaf</span>, <span class="symbol">'node</span>, <span class="symbol">'empty</span>) open_tree_visitor -> <span class="symbol">'a</span></span><br><span class="line"> <span class="keyword">end</span></span><br><span class="line"></span><br><span class="line"><span class="keyword">and</span> leaf (i : <span class="built_in">int</span>) = </span><br><span class="line"> <span class="keyword">object</span> (self:<span class="symbol">'self</span>)</span><br><span class="line"> <span class="keyword">inherit</span> tree</span><br><span class="line"> <span class="keyword">method</span> get = i</span><br><span class="line"> <span class="keyword">method</span> accept v = v#visit_leaf (self :> leaf)</span><br><span class="line"> <span class="keyword">end</span></span><br><span class="line"></span><br><span class="line"><span class="keyword">and</span> node (x : tree) (y: tree) = </span><br><span class="line"> <span class="keyword">object</span> (self:<span class="symbol">'self</span>)</span><br><span class="line"> <span class="keyword">inherit</span> tree</span><br><span class="line"> <span class="keyword">method</span> left = x</span><br><span class="line"> <span class="keyword">method</span> right = y</span><br><span class="line"> <span class="keyword">method</span> accept v = v#visit_node (self :> node)</span><br><span class="line"> <span class="keyword">end</span></span><br><span class="line"></span><br><span class="line"><span class="keyword">and</span> empty = </span><br><span class="line"> <span class="keyword">object</span> (self:<span class="symbol">'self</span>)</span><br><span class="line"> <span class="keyword">inherit</span> tree</span><br><span class="line"> <span class="keyword">method</span> accept v = v#visit_empty (self :> empty)</span><br><span class="line"> <span class="keyword">end</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="/2023/06/29/%E4%BA%8C%E3%80%87%E4%BA%8C%E4%B8%89%E5%B9%B4%E5%85%AD%E6%9C%88%E4%BA%8C%E5%8D%81%E4%B9%9D%E6%97%A5/">Prev</a> - </div> - - </div> - <div class="next-item"> - - <div class="icon arrow-right"></div> - <div class="post-link"> - <a 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