Site updated: 2017-05-11 23:34:45

Author: nameoverflow

2016/05/14/什么是函数式编程思维/index.html

@@ -82,16 +82,7 @@ <h1>什么是函数式编程思维？</h1>
 <p>这是什么意思呢？</p>
 <p>假如，现在你来到 google 面试，面试官让你把二叉树镜像反转一下（大雾</p>
 <p>几乎不假思索的，就可以写出这样的 Python 代码：</p>
-<pre><code class="python"><span class="function"><span class="keyword">def</span> <span class="title">invertTree</span><span class="params">(root)</span>:</span>
-    <span class="keyword">if</span> root <span class="keyword">is</span> <span class="keyword">None</span>:
-        <span class="keyword">return</span> <span class="keyword">None</span>
-    <span class="keyword">if</span> root.left:
-        invertTree(root.left)
-    <span class="keyword">if</span> root.right:
-        invertTree(root.right)
-    root.left, root.right = root.right, root.left
-    <span class="keyword">return</span> root
-</code></pre>
+<figure class="highlight python"><table><tr><td class="code"><pre><div class="line"></div><div class="line"><span class="function"><span class="keyword">def</span> <span class="title">invertTree</span><span class="params">(root)</span>:</span></div><div class="line"></div><div class="line">    <span class="keyword">if</span> root <span class="keyword">is</span> <span class="keyword">None</span>:</div><div class="line"></div><div class="line">        <span class="keyword">return</span> <span class="keyword">None</span></div><div class="line"></div><div class="line">    <span class="keyword">if</span> root.left:</div><div class="line"></div><div class="line">        invertTree(root.left)</div><div class="line"></div><div class="line">    <span class="keyword">if</span> root.right:</div><div class="line"></div><div class="line">        invertTree(root.right)</div><div class="line"></div><div class="line">    root.left, root.right = root.right, root.left</div><div class="line"></div><div class="line">    <span class="keyword">return</span> root</div></pre></td></tr></table></figure>
 <p>好了，现在停下来看看这段代码究竟代表着什么——</p>
 <p>它的含义是：首先判断节点是否为空；然后翻转左树；然后翻转右树；最后左右互换。</p>
 <p>这就是命令式编程——你要做什么事情，你得把达到目的的步骤详细的描述出来，然后交给机器去运行。</p>
@@ -101,20 +92,9 @@ <h1>什么是函数式编程思维？</h1>
 <p>所谓“翻转二叉树”，可以看做是要得到一颗和原来二叉树对称的新二叉树。</p>
 <p>这颗新二叉树的特点是每一个节点都递归地和原树相反。</p>
 <p>用 haskell 代码表达出来就是：</p>
-<pre><code class="haskell"><span class="class"><span class="keyword">data</span> <span class="type">Tree</span> a = <span class="type">Node</span> a (<span class="type">Maybe</span> (<span class="type">Tree</span> <span class="title">a</span>)) (<span class="type">Maybe</span> (<span class="type">Tree</span> <span class="title">a</span>))</span>
-            <span class="keyword">deriving</span> (<span class="type">Show</span>, <span class="type">Eq</span>)
-
-<span class="title">invert</span> :: <span class="type">Maybe</span> (<span class="type">Tree</span> a) -&gt; <span class="type">Maybe</span> (<span class="type">Tree</span> a)
-<span class="title">invert</span> <span class="type">Nothing</span> = <span class="type">Nothing</span>
-<span class="title">invert</span> (<span class="type">Just</span> <span class="type">Node</span> v l r) = <span class="type">Just</span> (<span class="type">Node</span> v (invert r) (invert l))
-</code></pre>
+<figure class="highlight haskell"><table><tr><td class="code"><pre><div class="line"><span class="class"><span class="keyword">data</span> <span class="type">Tree</span> a = <span class="type">Nil</span> | <span class="type">Node</span> a (<span class="type">Tree</span> <span class="title">a</span>) (<span class="type">Tree</span> <span class="title">a</span>)</span></div><div class="line">            <span class="keyword">deriving</span> (<span class="type">Show</span>, <span class="type">Eq</span>)</div><div class="line"></div><div class="line"><span class="title">invert</span> :: <span class="type">Tree</span> a -&gt; <span class="type">Tree</span> a</div><div class="line"><span class="title">invert</span> <span class="type">Nil</span> = <span class="type">Nil</span></div><div class="line"><span class="title">invert</span> (<span class="type">Node</span> v l r) = <span class="type">Node</span> v (invert r) (invert l)</div></pre></td></tr></table></figure>
 <p>（防止看不懂，翻译成等价的 python ）</p>
-<pre><code class="python"><span class="function"><span class="keyword">def</span> <span class="title">invert</span><span class="params">(node)</span>:</span>
-    <span class="keyword">if</span> node <span class="keyword">is</span> <span class="keyword">None</span>:
-        <span class="keyword">return</span> <span class="keyword">None</span>
-    <span class="keyword">else</span>
-        <span class="keyword">return</span> Tree(node.value, invert(node.right), invert(node.left))
-</code></pre>
+<figure class="highlight python"><table><tr><td class="code"><pre><div class="line"></div><div class="line"><span class="function"><span class="keyword">def</span> <span class="title">invert</span><span class="params">(node)</span>:</span></div><div class="line"></div><div class="line">    <span class="keyword">if</span> node <span class="keyword">is</span> <span class="keyword">None</span>:</div><div class="line"></div><div class="line">        <span class="keyword">return</span> <span class="keyword">None</span></div><div class="line"></div><div class="line">    <span class="keyword">else</span></div><div class="line"></div><div class="line">        <span class="keyword">return</span> Tree(node.value, invert(node.right), invert(node.left))</div></pre></td></tr></table></figure>
 <p>这段代码体现的思维，就是旧树到新树的映射——对一颗二叉树而言，它的镜像树就是左右节点递归镜像的树。</p>
 <p>这段代码最终达到的目的同样是翻转二叉树，但是它得到结果的方式和 python 代码有着本质的差别：通过描述一个 旧树-&gt;新树 的映射，而不是描述“从旧树得到新树应该怎样做”来达到目的。</p>
 <p>那么这样思考有什么好处呢？</p>

index.html

@@ -341,16 +341,7 @@ <h1>
 <p>这是什么意思呢？</p>
 <p>假如，现在你来到 google 面试，面试官让你把二叉树镜像反转一下（大雾</p>
 <p>几乎不假思索的，就可以写出这样的 Python 代码：</p>
-<pre><code class="python"><span class="function"><span class="keyword">def</span> <span class="title">invertTree</span><span class="params">(root)</span>:</span>
-    <span class="keyword">if</span> root <span class="keyword">is</span> <span class="keyword">None</span>:
-        <span class="keyword">return</span> <span class="keyword">None</span>
-    <span class="keyword">if</span> root.left:
-        invertTree(root.left)
-    <span class="keyword">if</span> root.right:
-        invertTree(root.right)
-    root.left, root.right = root.right, root.left
-    <span class="keyword">return</span> root
-</code></pre>
+<figure class="highlight python"><table><tr><td class="code"><pre><div class="line"></div><div class="line"><span class="function"><span class="keyword">def</span> <span class="title">invertTree</span><span class="params">(root)</span>:</span></div><div class="line"></div><div class="line">    <span class="keyword">if</span> root <span class="keyword">is</span> <span class="keyword">None</span>:</div><div class="line"></div><div class="line">        <span class="keyword">return</span> <span class="keyword">None</span></div><div class="line"></div><div class="line">    <span class="keyword">if</span> root.left:</div><div class="line"></div><div class="line">        invertTree(root.left)</div><div class="line"></div><div class="line">    <span class="keyword">if</span> root.right:</div><div class="line"></div><div class="line">        invertTree(root.right)</div><div class="line"></div><div class="line">    root.left, root.right = root.right, root.left</div><div class="line"></div><div class="line">    <span class="keyword">return</span> root</div></pre></td></tr></table></figure>
 <p>好了，现在停下来看看这段代码究竟代表着什么——</p>
 <p>它的含义是：首先判断节点是否为空；然后翻转左树；然后翻转右树；最后左右互换。</p>
 <p>这就是命令式编程——你要做什么事情，你得把达到目的的步骤详细的描述出来，然后交给机器去运行。</p>
@@ -360,20 +351,9 @@ <h1>
 <p>所谓“翻转二叉树”，可以看做是要得到一颗和原来二叉树对称的新二叉树。</p>
 <p>这颗新二叉树的特点是每一个节点都递归地和原树相反。</p>
 <p>用 haskell 代码表达出来就是：</p>
-<pre><code class="haskell"><span class="class"><span class="keyword">data</span> <span class="type">Tree</span> a = <span class="type">Node</span> a (<span class="type">Maybe</span> (<span class="type">Tree</span> <span class="title">a</span>)) (<span class="type">Maybe</span> (<span class="type">Tree</span> <span class="title">a</span>))</span>
-            <span class="keyword">deriving</span> (<span class="type">Show</span>, <span class="type">Eq</span>)
-
-<span class="title">invert</span> :: <span class="type">Maybe</span> (<span class="type">Tree</span> a) -&gt; <span class="type">Maybe</span> (<span class="type">Tree</span> a)
-<span class="title">invert</span> <span class="type">Nothing</span> = <span class="type">Nothing</span>
-<span class="title">invert</span> (<span class="type">Just</span> <span class="type">Node</span> v l r) = <span class="type">Just</span> (<span class="type">Node</span> v (invert r) (invert l))
-</code></pre>
+<figure class="highlight haskell"><table><tr><td class="code"><pre><div class="line"><span class="class"><span class="keyword">data</span> <span class="type">Tree</span> a = <span class="type">Nil</span> | <span class="type">Node</span> a (<span class="type">Tree</span> <span class="title">a</span>) (<span class="type">Tree</span> <span class="title">a</span>)</span></div><div class="line">            <span class="keyword">deriving</span> (<span class="type">Show</span>, <span class="type">Eq</span>)</div><div class="line"></div><div class="line"><span class="title">invert</span> :: <span class="type">Tree</span> a -&gt; <span class="type">Tree</span> a</div><div class="line"><span class="title">invert</span> <span class="type">Nil</span> = <span class="type">Nil</span></div><div class="line"><span class="title">invert</span> (<span class="type">Node</span> v l r) = <span class="type">Node</span> v (invert r) (invert l)</div></pre></td></tr></table></figure>
 <p>（防止看不懂，翻译成等价的 python ）</p>
-<pre><code class="python"><span class="function"><span class="keyword">def</span> <span class="title">invert</span><span class="params">(node)</span>:</span>
-    <span class="keyword">if</span> node <span class="keyword">is</span> <span class="keyword">None</span>:
-        <span class="keyword">return</span> <span class="keyword">None</span>
-    <span class="keyword">else</span>
-        <span class="keyword">return</span> Tree(node.value, invert(node.right), invert(node.left))
-</code></pre>
+<figure class="highlight python"><table><tr><td class="code"><pre><div class="line"></div><div class="line"><span class="function"><span class="keyword">def</span> <span class="title">invert</span><span class="params">(node)</span>:</span></div><div class="line"></div><div class="line">    <span class="keyword">if</span> node <span class="keyword">is</span> <span class="keyword">None</span>:</div><div class="line"></div><div class="line">        <span class="keyword">return</span> <span class="keyword">None</span></div><div class="line"></div><div class="line">    <span class="keyword">else</span></div><div class="line"></div><div class="line">        <span class="keyword">return</span> Tree(node.value, invert(node.right), invert(node.left))</div></pre></td></tr></table></figure>
 <p>这段代码体现的思维，就是旧树到新树的映射——对一颗二叉树而言，它的镜像树就是左右节点递归镜像的树。</p>
 <p>这段代码最终达到的目的同样是翻转二叉树，但是它得到结果的方式和 python 代码有着本质的差别：通过描述一个 旧树-&gt;新树 的映射，而不是描述“从旧树得到新树应该怎样做”来达到目的。</p>
 <p>那么这样思考有什么好处呢？</p>

tags/functional-programming/index.html

@@ -111,16 +111,7 @@ <h1>
 <p>这是什么意思呢？</p>
 <p>假如，现在你来到 google 面试，面试官让你把二叉树镜像反转一下（大雾</p>
 <p>几乎不假思索的，就可以写出这样的 Python 代码：</p>
-<pre><code class="python"><span class="function"><span class="keyword">def</span> <span class="title">invertTree</span><span class="params">(root)</span>:</span>
-    <span class="keyword">if</span> root <span class="keyword">is</span> <span class="keyword">None</span>:
-        <span class="keyword">return</span> <span class="keyword">None</span>
-    <span class="keyword">if</span> root.left:
-        invertTree(root.left)
-    <span class="keyword">if</span> root.right:
-        invertTree(root.right)
-    root.left, root.right = root.right, root.left
-    <span class="keyword">return</span> root
-</code></pre>
+<figure class="highlight python"><table><tr><td class="code"><pre><div class="line"></div><div class="line"><span class="function"><span class="keyword">def</span> <span class="title">invertTree</span><span class="params">(root)</span>:</span></div><div class="line"></div><div class="line">    <span class="keyword">if</span> root <span class="keyword">is</span> <span class="keyword">None</span>:</div><div class="line"></div><div class="line">        <span class="keyword">return</span> <span class="keyword">None</span></div><div class="line"></div><div class="line">    <span class="keyword">if</span> root.left:</div><div class="line"></div><div class="line">        invertTree(root.left)</div><div class="line"></div><div class="line">    <span class="keyword">if</span> root.right:</div><div class="line"></div><div class="line">        invertTree(root.right)</div><div class="line"></div><div class="line">    root.left, root.right = root.right, root.left</div><div class="line"></div><div class="line">    <span class="keyword">return</span> root</div></pre></td></tr></table></figure>
 <p>好了，现在停下来看看这段代码究竟代表着什么——</p>
 <p>它的含义是：首先判断节点是否为空；然后翻转左树；然后翻转右树；最后左右互换。</p>
 <p>这就是命令式编程——你要做什么事情，你得把达到目的的步骤详细的描述出来，然后交给机器去运行。</p>
@@ -130,20 +121,9 @@ <h1>
 <p>所谓“翻转二叉树”，可以看做是要得到一颗和原来二叉树对称的新二叉树。</p>
 <p>这颗新二叉树的特点是每一个节点都递归地和原树相反。</p>
 <p>用 haskell 代码表达出来就是：</p>
-<pre><code class="haskell"><span class="class"><span class="keyword">data</span> <span class="type">Tree</span> a = <span class="type">Node</span> a (<span class="type">Maybe</span> (<span class="type">Tree</span> <span class="title">a</span>)) (<span class="type">Maybe</span> (<span class="type">Tree</span> <span class="title">a</span>))</span>
-            <span class="keyword">deriving</span> (<span class="type">Show</span>, <span class="type">Eq</span>)
-
-<span class="title">invert</span> :: <span class="type">Maybe</span> (<span class="type">Tree</span> a) -&gt; <span class="type">Maybe</span> (<span class="type">Tree</span> a)
-<span class="title">invert</span> <span class="type">Nothing</span> = <span class="type">Nothing</span>
-<span class="title">invert</span> (<span class="type">Just</span> <span class="type">Node</span> v l r) = <span class="type">Just</span> (<span class="type">Node</span> v (invert r) (invert l))
-</code></pre>
+<figure class="highlight haskell"><table><tr><td class="code"><pre><div class="line"><span class="class"><span class="keyword">data</span> <span class="type">Tree</span> a = <span class="type">Nil</span> | <span class="type">Node</span> a (<span class="type">Tree</span> <span class="title">a</span>) (<span class="type">Tree</span> <span class="title">a</span>)</span></div><div class="line">            <span class="keyword">deriving</span> (<span class="type">Show</span>, <span class="type">Eq</span>)</div><div class="line"></div><div class="line"><span class="title">invert</span> :: <span class="type">Tree</span> a -&gt; <span class="type">Tree</span> a</div><div class="line"><span class="title">invert</span> <span class="type">Nil</span> = <span class="type">Nil</span></div><div class="line"><span class="title">invert</span> (<span class="type">Node</span> v l r) = <span class="type">Node</span> v (invert r) (invert l)</div></pre></td></tr></table></figure>
 <p>（防止看不懂，翻译成等价的 python ）</p>
-<pre><code class="python"><span class="function"><span class="keyword">def</span> <span class="title">invert</span><span class="params">(node)</span>:</span>
-    <span class="keyword">if</span> node <span class="keyword">is</span> <span class="keyword">None</span>:
-        <span class="keyword">return</span> <span class="keyword">None</span>
-    <span class="keyword">else</span>
-        <span class="keyword">return</span> Tree(node.value, invert(node.right), invert(node.left))
-</code></pre>
+<figure class="highlight python"><table><tr><td class="code"><pre><div class="line"></div><div class="line"><span class="function"><span class="keyword">def</span> <span class="title">invert</span><span class="params">(node)</span>:</span></div><div class="line"></div><div class="line">    <span class="keyword">if</span> node <span class="keyword">is</span> <span class="keyword">None</span>:</div><div class="line"></div><div class="line">        <span class="keyword">return</span> <span class="keyword">None</span></div><div class="line"></div><div class="line">    <span class="keyword">else</span></div><div class="line"></div><div class="line">        <span class="keyword">return</span> Tree(node.value, invert(node.right), invert(node.left))</div></pre></td></tr></table></figure>
 <p>这段代码体现的思维，就是旧树到新树的映射——对一颗二叉树而言，它的镜像树就是左右节点递归镜像的树。</p>
 <p>这段代码最终达到的目的同样是翻转二叉树，但是它得到结果的方式和 python 代码有着本质的差别：通过描述一个 旧树-&gt;新树 的映射，而不是描述“从旧树得到新树应该怎样做”来达到目的。</p>
 <p>那么这样思考有什么好处呢？</p>