chapter12.html

《C++编程思想》中文版。。。。。。。。。。。。。

<BLOCKQUOTE><FONT SIZE = "+1"><PRE><font color=#009900>//: C12:IntegerTest.cpp</font>
<font color=#009900>//{L} Integer</font>
#include <font color=#004488>"Integer.h"</font>
#include &lt;fstream&gt;
<font color=#0000ff>using</font> <font color=#0000ff>namespace</font> std;
ofstream out(<font color=#004488>"IntegerTest.out"</font>);

<font color=#0000ff>void</font> h(Integer&amp; c1, Integer&amp; c2) {
  <font color=#009900>// A complex expression:</font>
  c1 += c1 * c2 + c2 % c1;
  #define TRY(OP) \
    out &lt;&lt; <font color=#004488>"c1 = "</font>; c1.print(out); \
    out &lt;&lt; <font color=#004488>", c2 = "</font>; c2.print(out); \
    out &lt;&lt; <font color=#004488>";  c1 "</font> #OP <font color=#004488>" c2 produces "</font>; \
    (c1 OP c2).print(out); \
    out &lt;&lt; endl;
  TRY(+) TRY(-) TRY(*) TRY(/)
  TRY(%) TRY(^) TRY(&amp;) TRY(|)
  TRY(&lt;&lt;) TRY(&gt;&gt;) TRY(+=) TRY(-=)
  TRY(*=) TRY(/=) TRY(%=) TRY(^=)
  TRY(&amp;=) TRY(|=) TRY(&gt;&gt;=) TRY(&lt;&lt;=)
  <font color=#009900>// Conditionals:</font>
  #define TRYC(OP) \
    out &lt;&lt; <font color=#004488>"c1 = "</font>; c1.print(out); \
    out &lt;&lt; <font color=#004488>", c2 = "</font>; c2.print(out); \
    out &lt;&lt; <font color=#004488>";  c1 "</font> #OP <font color=#004488>" c2 produces "</font>; \
    out &lt;&lt; (c1 OP c2); \
    out &lt;&lt; endl;
  TRYC(&lt;) TRYC(&gt;) TRYC(==) TRYC(!=) TRYC(&lt;=)
  TRYC(&gt;=) TRYC(&amp;&amp;) TRYC(||)
} 

<font color=#0000ff>int</font> main() {
  cout &lt;&lt; <font color=#004488>"friend functions"</font> &lt;&lt; endl;
  Integer c1(47), c2(9);
  h(c1, c2);
} <font color=#009900>///:~</font></PRE></FONT></BLOCKQUOTE>


<BLOCKQUOTE><FONT SIZE = "+1"><PRE><font color=#009900>//: C12:Byte.h</font>
<font color=#009900>// Member overloaded operators</font>
#ifndef BYTE_H
#define BYTE_H
#include <font color=#004488>"../require.h"</font>
#include &lt;iostream&gt;
<font color=#009900>// Member functions (implicit "this"):</font>
<font color=#0000ff>class</font> Byte { 
  <font color=#0000ff>unsigned</font> <font color=#0000ff>char</font> b;
<font color=#0000ff>public</font>:
  Byte(<font color=#0000ff>unsigned</font> <font color=#0000ff>char</font> bb = 0) : b(bb) {}
  <font color=#009900>// No side effects: const member function:</font>
  <font color=#0000ff>const</font> Byte
    <font color=#0000ff>operator</font>+(<font color=#0000ff>const</font> Byte&amp; right) <font color=#0000ff>const</font> {
    <font color=#0000ff>return</font> Byte(b + right.b);
  }
  <font color=#0000ff>const</font> Byte
    <font color=#0000ff>operator</font>-(<font color=#0000ff>const</font> Byte&amp; right) <font color=#0000ff>const</font> {
    <font color=#0000ff>return</font> Byte(b - right.b);
  }
  <font color=#0000ff>const</font> Byte
    <font color=#0000ff>operator</font>*(<font color=#0000ff>const</font> Byte&amp; right) <font color=#0000ff>const</font> {
    <font color=#0000ff>return</font> Byte(b * right.b);
  }
  <font color=#0000ff>const</font> Byte
    <font color=#0000ff>operator</font>/(<font color=#0000ff>const</font> Byte&amp; right) <font color=#0000ff>const</font> {
    require(right.b != 0, <font color=#004488>"divide by zero"</font>);
    <font color=#0000ff>return</font> Byte(b / right.b);
  }
  <font color=#0000ff>const</font> Byte
    <font color=#0000ff>operator</font>%(<font color=#0000ff>const</font> Byte&amp; right) <font color=#0000ff>const</font> {
    require(right.b != 0, <font color=#004488>"modulo by zero"</font>);
    <font color=#0000ff>return</font> Byte(b % right.b);
  }
  <font color=#0000ff>const</font> Byte
    <font color=#0000ff>operator</font>^(<font color=#0000ff>const</font> Byte&amp; right) <font color=#0000ff>const</font> {
    <font color=#0000ff>return</font> Byte(b ^ right.b);
  }
  <font color=#0000ff>const</font> Byte
    <font color=#0000ff>operator</font>&amp;(<font color=#0000ff>const</font> Byte&amp; right) <font color=#0000ff>const</font> {
    <font color=#0000ff>return</font> Byte(b &amp; right.b);
  }
  <font color=#0000ff>const</font> Byte
    <font color=#0000ff>operator</font>|(<font color=#0000ff>const</font> Byte&amp; right) <font color=#0000ff>const</font> {
    <font color=#0000ff>return</font> Byte(b | right.b);
  }
  <font color=#0000ff>const</font> Byte
    <font color=#0000ff>operator</font>&lt;&lt;(<font color=#0000ff>const</font> Byte&amp; right) <font color=#0000ff>const</font> {
    <font color=#0000ff>return</font> Byte(b &lt;&lt; right.b);
  }
  <font color=#0000ff>const</font> Byte
    <font color=#0000ff>operator</font>&gt;&gt;(<font color=#0000ff>const</font> Byte&amp; right) <font color=#0000ff>const</font> {
    <font color=#0000ff>return</font> Byte(b &gt;&gt; right.b);
  }
  <font color=#009900>// Assignments modify &amp; return lvalue.</font>
  <font color=#009900>// operator= can only be a member function:</font>
  Byte&amp; <font color=#0000ff>operator</font>=(<font color=#0000ff>const</font> Byte&amp; right) {
    <font color=#009900>// Handle self-assignment:</font>
    <font color=#0000ff>if</font>(<font color=#0000ff>this</font> == &amp;right) <font color=#0000ff>return</font> *<font color=#0000ff>this</font>;
    b = right.b;
    <font color=#0000ff>return</font> *<font color=#0000ff>this</font>;
  }
  Byte&amp; <font color=#0000ff>operator</font>+=(<font color=#0000ff>const</font> Byte&amp; right) {
    <font color=#0000ff>if</font>(<font color=#0000ff>this</font> == &amp;right) {<font color=#009900>/* self-assignment */</font>}
    b += right.b;
    <font color=#0000ff>return</font> *<font color=#0000ff>this</font>;
  }
  Byte&amp; <font color=#0000ff>operator</font>-=(<font color=#0000ff>const</font> Byte&amp; right) {
    <font color=#0000ff>if</font>(<font color=#0000ff>this</font> == &amp;right) {<font color=#009900>/* self-assignment */</font>}
    b -= right.b;
    <font color=#0000ff>return</font> *<font color=#0000ff>this</font>;
  }
  Byte&amp; <font color=#0000ff>operator</font>*=(<font color=#0000ff>const</font> Byte&amp; right) {
    <font color=#0000ff>if</font>(<font color=#0000ff>this</font> == &amp;right) {<font color=#009900>/* self-assignment */</font>}
    b *= right.b;
    <font color=#0000ff>return</font> *<font color=#0000ff>this</font>;
  }
  Byte&amp; <font color=#0000ff>operator</font>/=(<font color=#0000ff>const</font> Byte&amp; right) {
    require(right.b != 0, <font color=#004488>"divide by zero"</font>);
    <font color=#0000ff>if</font>(<font color=#0000ff>this</font> == &amp;right) {<font color=#009900>/* self-assignment */</font>}
    b /= right.b;
    <font color=#0000ff>return</font> *<font color=#0000ff>this</font>;
  }
  Byte&amp; <font color=#0000ff>operator</font>%=(<font color=#0000ff>const</font> Byte&amp; right) {
    require(right.b != 0, <font color=#004488>"modulo by zero"</font>);
    <font color=#0000ff>if</font>(<font color=#0000ff>this</font> == &amp;right) {<font color=#009900>/* self-assignment */</font>}
    b %= right.b;
    <font color=#0000ff>return</font> *<font color=#0000ff>this</font>;
  }
  Byte&amp; <font color=#0000ff>operator</font>^=(<font color=#0000ff>const</font> Byte&amp; right) {
    <font color=#0000ff>if</font>(<font color=#0000ff>this</font> == &amp;right) {<font color=#009900>/* self-assignment */</font>}
    b ^= right.b;
    <font color=#0000ff>return</font> *<font color=#0000ff>this</font>;
  }
  Byte&amp; <font color=#0000ff>operator</font>&amp;=(<font color=#0000ff>const</font> Byte&amp; right) {
    <font color=#0000ff>if</font>(<font color=#0000ff>this</font> == &amp;right) {<font color=#009900>/* self-assignment */</font>}
    b &amp;= right.b;
    <font color=#0000ff>return</font> *<font color=#0000ff>this</font>;
  }
  Byte&amp; <font color=#0000ff>operator</font>|=(<font color=#0000ff>const</font> Byte&amp; right) {
    <font color=#0000ff>if</font>(<font color=#0000ff>this</font> == &amp;right) {<font color=#009900>/* self-assignment */</font>}
    b |= right.b;
    <font color=#0000ff>return</font> *<font color=#0000ff>this</font>;
  }
  Byte&amp; <font color=#0000ff>operator</font>&gt;&gt;=(<font color=#0000ff>const</font> Byte&amp; right) {
    <font color=#0000ff>if</font>(<font color=#0000ff>this</font> == &amp;right) {<font color=#009900>/* self-assignment */</font>}
    b &gt;&gt;= right.b;
    <font color=#0000ff>return</font> *<font color=#0000ff>this</font>;
  }
  Byte&amp; <font color=#0000ff>operator</font>&lt;&lt;=(<font color=#0000ff>const</font> Byte&amp; right) {
    <font color=#0000ff>if</font>(<font color=#0000ff>this</font> == &amp;right) {<font color=#009900>/* self-assignment */</font>}
    b &lt;&lt;= right.b;
    <font color=#0000ff>return</font> *<font color=#0000ff>this</font>;
  }
  <font color=#009900>// Conditional operators return true/false:</font>
  <font color=#0000ff>int</font> <font color=#0000ff>operator</font>==(<font color=#0000ff>const</font> Byte&amp; right) <font color=#0000ff>const</font> {
      <font color=#0000ff>return</font> b == right.b;
  }
  <font color=#0000ff>int</font> <font color=#0000ff>operator</font>!=(<font color=#0000ff>const</font> Byte&amp; right) <font color=#0000ff>const</font> {
      <font color=#0000ff>return</font> b != right.b;
  }
  <font color=#0000ff>int</font> <font color=#0000ff>operator</font>&lt;(<font color=#0000ff>const</font> Byte&amp; right) <font color=#0000ff>const</font> {
      <font color=#0000ff>return</font> b &lt; right.b;
  }
  <font color=#0000ff>int</font> <font color=#0000ff>operator</font>&gt;(<font color=#0000ff>const</font> Byte&amp; right) <font color=#0000ff>const</font> {
      <font color=#0000ff>return</font> b &gt; right.b;
  }
  <font color=#0000ff>int</font> <font color=#0000ff>operator</font>&lt;=(<font color=#0000ff>const</font> Byte&amp; right) <font color=#0000ff>const</font> {
      <font color=#0000ff>return</font> b &lt;= right.b;
  }
  <font color=#0000ff>int</font> <font color=#0000ff>operator</font>&gt;=(<font color=#0000ff>const</font> Byte&amp; right) <font color=#0000ff>const</font> {
      <font color=#0000ff>return</font> b &gt;= right.b;
  }
  <font color=#0000ff>int</font> <font color=#0000ff>operator</font>&amp;&amp;(<font color=#0000ff>const</font> Byte&amp; right) <font color=#0000ff>const</font> {
      <font color=#0000ff>return</font> b &amp;&amp; right.b;
  }
  <font color=#0000ff>int</font> <font color=#0000ff>operator</font>||(<font color=#0000ff>const</font> Byte&amp; right) <font color=#0000ff>const</font> {
      <font color=#0000ff>return</font> b || right.b;
  }
  <font color=#009900>// Write the contents to an ostream:</font>
  <font color=#0000ff>void</font> print(std::ostream&amp; os) <font color=#0000ff>const</font> {
    os &lt;&lt; <font color=#004488>"0x"</font> &lt;&lt; std::hex &lt;&lt; <font color=#0000ff>int</font>(b) &lt;&lt; std::dec;
  }
}; 
#endif <font color=#009900>// BYTE_H ///:~</font></PRE></FONT></BLOCKQUOTE>


<BLOCKQUOTE><FONT SIZE = "+1"><PRE><font color=#009900>//: C12:ByteTest.cpp</font>
#include <font color=#004488>"Byte.h"</font>
#include &lt;fstream&gt;
<font color=#0000ff>using</font> <font color=#0000ff>namespace</font> std;
ofstream out(<font color=#004488>"ByteTest.out"</font>);

<font color=#0000ff>void</font> k(Byte&amp; b1, Byte&amp; b2) {
  b1 = b1 * b2 + b2 % b1;

  #define TRY2(OP) \
    out &lt;&lt; <font color=#004488>"b1 = "</font>; b1.print(out); \
    out &lt;&lt; <font color=#004488>", b2 = "</font>; b2.print(out); \
    out &lt;&lt; <font color=#004488>";  b1 "</font> #OP <font color=#004488>" b2 produces "</font>; \
    (b1 OP b2).print(out); \
    out &lt;&lt; endl;

  b1 = 9; b2 = 47;
  TRY2(+) TRY2(-) TRY2(*) TRY2(/)
  TRY2(%) TRY2(^) TRY2(&amp;) TRY2(|)
  TRY2(&lt;&lt;) TRY2(&gt;&gt;) TRY2(+=) TRY2(-=)
  TRY2(*=) TRY2(/=) TRY2(%=) TRY2(^=)
  TRY2(&amp;=) TRY2(|=) TRY2(&gt;&gt;=) TRY2(&lt;&lt;=)
  TRY2(=) <font color=#009900>// Assignment operator</font>

  <font color=#009900>// Conditionals:</font>
  #define TRYC2(OP) \
    out &lt;&lt; <font color=#004488>"b1 = "</font>; b1.print(out); \
    out &lt;&lt; <font color=#004488>", b2 = "</font>; b2.print(out); \
    out &lt;&lt; <font color=#004488>";  b1 "</font> #OP <font color=#004488>" b2 produces "</font>; \
    out &lt;&lt; (b1 OP b2); \
    out &lt;&lt; endl;

  b1 = 9; b2 = 47;
  TRYC2(&lt;) TRYC2(&gt;) TRYC2(==) TRYC2(!=) TRYC2(&lt;=)
  TRYC2(&gt;=) TRYC2(&amp;&amp;) TRYC2(||)

  <font color=#009900>// Chained assignment:</font>
  Byte b3 = 92;