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@@ -45,7 +45,7 @@ pattern to write your own Go line filters.</p> |
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- <a href="http://play.golang.org/p/OSS71nSpkV"><img title="Run code" src="play.png" class="run" /></a>
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+ <a href="http://play.golang.org/p/mpYwOHj2ma"><img title="Run code" src="play.png" class="run" /></a>
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<div class="highlight"><pre><span class="kn">package</span> <span class="nx">main</span>
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</pre></div>
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@@ -61,7 +61,6 @@ pattern to write your own Go line filters.</p> |
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<div class="highlight"><pre><span class="kn">import</span> <span class="p">(</span>
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<span class="s">"bufio"</span>
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<span class="s">"fmt"</span>
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- <span class="s">"io"</span>
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<span class="s">"os"</span>
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<span class="s">"strings"</span>
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<span class="p">)</span>
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@@ -85,83 +84,70 @@ pattern to write your own Go line filters.</p> |
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<tr>
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<td class="docs">
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<p>Wrapping the unbuffered <code>os.Stdin</code> with a buffered
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-reader gives us a convenient <code>ReadString</code> method
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-that we’ll use to read input line-by-line.</p>
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+scanner gives us a convenient <code>Scan</code> method that
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+advances the scanner to the next token; which is
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+the next line in the default scanner.</p>
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<td class="code leading">
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- <div class="highlight"><pre> <span class="nx">rdr</span> <span class="o">:=</span> <span class="nx">bufio</span><span class="p">.</span><span class="nx">NewReader</span><span class="p">(</span><span class="nx">os</span><span class="p">.</span><span class="nx">Stdin</span><span class="p">)</span>
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- <span class="nx">out</span> <span class="o">:=</span> <span class="nx">os</span><span class="p">.</span><span class="nx">Stdout</span>
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+ <div class="highlight"><pre> <span class="nx">scanner</span> <span class="o">:=</span> <span class="nx">bufio</span><span class="p">.</span><span class="nx">NewScanner</span><span class="p">(</span><span class="nx">os</span><span class="p">.</span><span class="nx">Stdin</span><span class="p">)</span>
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</pre></div>
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<td class="docs">
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- <p><code>ReadString</code> returns the next string from the
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-input up to the given separator byte. We give the
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-newline byte <code>'\n'</code> as our separator so we’ll get
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-successive input lines.</p>
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+ <p><code>Text</code> returns the current token, here the next line,
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+from the input.</p>
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<td class="code leading">
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- <div class="highlight"><pre> <span class="k">for</span> <span class="p">{</span>
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- <span class="k">switch</span> <span class="nx">line</span><span class="p">,</span> <span class="nx">err</span> <span class="o">:=</span> <span class="nx">rdr</span><span class="p">.</span><span class="nx">ReadString</span><span class="p">(</span><span class="sc">'\n'</span><span class="p">);</span> <span class="nx">err</span> <span class="p">{</span>
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+ <div class="highlight"><pre> <span class="k">for</span> <span class="nx">scanner</span><span class="p">.</span><span class="nx">Scan</span><span class="p">()</span> <span class="p">{</span>
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</pre></div>
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</td>
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</tr>
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<td class="docs">
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- <p>If the read succeeded (the read <code>err</code> is nil),
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-write out out the uppercased line. Check for an
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-error on this write as we do on the read.</p>
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-
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+
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</td>
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<td class="code leading">
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- <div class="highlight"><pre> <span class="k">case</span> <span class="kc">nil</span><span class="p">:</span>
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- <span class="nx">ucl</span> <span class="o">:=</span> <span class="nx">strings</span><span class="p">.</span><span class="nx">ToUpper</span><span class="p">(</span><span class="nx">line</span><span class="p">)</span>
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- <span class="k">if</span> <span class="nx">_</span><span class="p">,</span> <span class="nx">err</span> <span class="p">=</span> <span class="nx">out</span><span class="p">.</span><span class="nx">WriteString</span><span class="p">(</span><span class="nx">ucl</span><span class="p">);</span> <span class="nx">err</span> <span class="o">!=</span> <span class="kc">nil</span> <span class="p">{</span>
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- <span class="nx">fmt</span><span class="p">.</span><span class="nx">Fprintln</span><span class="p">(</span><span class="nx">os</span><span class="p">.</span><span class="nx">Stderr</span><span class="p">,</span> <span class="s">"error:"</span><span class="p">,</span> <span class="nx">err</span><span class="p">)</span>
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- <span class="nx">os</span><span class="p">.</span><span class="nx">Exit</span><span class="p">(</span><span class="mi">1</span><span class="p">)</span>
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- <span class="p">}</span>
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+ <div class="highlight"><pre> <span class="nx">ucl</span> <span class="o">:=</span> <span class="nx">strings</span><span class="p">.</span><span class="nx">ToUpper</span><span class="p">(</span><span class="nx">scanner</span><span class="p">.</span><span class="nx">Text</span><span class="p">())</span>
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</pre></div>
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</td>
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</tr>
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<td class="docs">
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- <p>The <code>EOF</code> error is expected when we reach the
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-end of input, so exit gracefully in that case.</p>
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+ <p>Write out the uppercased line.</p>
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</td>
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<td class="code leading">
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- <div class="highlight"><pre> <span class="k">case</span> <span class="nx">io</span><span class="p">.</span><span class="nx">EOF</span><span class="p">:</span>
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- <span class="nx">os</span><span class="p">.</span><span class="nx">Exit</span><span class="p">(</span><span class="mi">0</span><span class="p">)</span>
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+ <div class="highlight"><pre> <span class="nx">fmt</span><span class="p">.</span><span class="nx">Println</span><span class="p">(</span><span class="nx">ucl</span><span class="p">)</span>
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+ <span class="p">}</span>
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</pre></div>
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</td>
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</tr>
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<td class="docs">
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- <p>Otherwise there’s a problem; print the
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-error and exit with non-zero status.</p>
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+ <p>Check for errors during <code>Scan</code>. End of file is
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+expected and not reported by <code>Scan</code> as an error.</p>
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</td>
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<td class="code">
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- <div class="highlight"><pre> <span class="k">default</span><span class="p">:</span>
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- <span class="nx">fmt</span><span class="p">.</span><span class="nx">Fprintln</span><span class="p">(</span><span class="nx">os</span><span class="p">.</span><span class="nx">Stderr</span><span class="p">,</span> <span class="s">"error:"</span><span class="p">,</span> <span class="nx">err</span><span class="p">)</span>
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- <span class="nx">os</span><span class="p">.</span><span class="nx">Exit</span><span class="p">(</span><span class="mi">1</span><span class="p">)</span>
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- <span class="p">}</span>
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+ <div class="highlight"><pre> <span class="k">if</span> <span class="nx">err</span> <span class="o">:=</span> <span class="nx">scanner</span><span class="p">.</span><span class="nx">Err</span><span class="p">();</span> <span class="nx">err</span> <span class="o">!=</span> <span class="kc">nil</span> <span class="p">{</span>
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+ <span class="nx">fmt</span><span class="p">.</span><span class="nx">Fprintln</span><span class="p">(</span><span class="nx">os</span><span class="p">.</span><span class="nx">Stderr</span><span class="p">,</span> <span class="s">"error:"</span><span class="p">,</span> <span class="nx">err</span><span class="p">)</span>
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+ <span class="nx">os</span><span class="p">.</span><span class="nx">Exit</span><span class="p">(</span><span class="mi">1</span><span class="p">)</span>
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<span class="p">}</span>
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<span class="p">}</span>
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</pre></div>
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