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<h3><span lang=EN-US>88. </span><span style='font-family:宋体;mso-ascii-font-family:
Arial;mso-hansi-font-family:Arial'>在用作算法和比较器（</span><span lang=EN-US>comparer</span><span
style='font-family:宋体;mso-ascii-font-family:Arial;mso-hansi-font-family:Arial'>）时，要优先用函数对象来代替函数。</span></h3>
<p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p>
<p class=MsoNormal><b style='mso-bidi-font-weight:normal'><span
style='font-family:宋体;mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:
"Times New Roman"'>摘要</span></b></p>
<p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-family:宋体;mso-ascii-font-family:"Times New Roman";
mso-hansi-font-family:"Times New Roman"'>与函数相比，对象更易于即插即用：优先给算法传递函数对象，而不是函数。关联型容器的比较器必须是函数对象。函数对象是可配接的（</span><span
lang=EN-US>adaptable</span><span style='font-family:宋体;mso-ascii-font-family:
"Times New Roman";mso-hansi-font-family:"Times New Roman"'>），而且和我们直觉相反的是，与函数相比，它们一般会产生更快的代码。</span></p>
<p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p>
<p class=MsoNormal><b style='mso-bidi-font-weight:normal'><span
style='font-family:宋体;mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:
"Times New Roman"'>讨论</span><a name=ch75index09></a><a name=ch75index08></a><a
name=ch75lev1sec2></a><span lang=EN-US><o:p></o:p></span></b></p>
<p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-family:宋体;mso-ascii-font-family:"Times New Roman";
mso-hansi-font-family:"Times New Roman"'>首先，使函数对象可配接比较容易，而且也应该始终这么做（参见第</span><span
lang=EN-US>89</span><span style='font-family:宋体;mso-ascii-font-family:"Times New Roman";
mso-hansi-font-family:"Times New Roman"'>条）。即使已经有了一个函数，有时为了使它可配接，还是必须用</span><span
lang=EN-US>ptr_fun</span><span style='font-family:宋体;mso-ascii-font-family:
"Times New Roman";mso-hansi-font-family:"Times New Roman"'>或</span><span
lang=EN-US>mem_fun</span><span style='font-family:宋体;mso-ascii-font-family:
"Times New Roman";mso-hansi-font-family:"Times New Roman"'>把它封装起来。例如，为了用</span><span
lang=EN-US>binder</span><span style='font-family:宋体;mso-ascii-font-family:"Times New Roman";
mso-hansi-font-family:"Times New Roman"'>来编写一个更为复杂的表达式（参见第</span><span
lang=EN-US>84</span><span style='font-family:宋体;mso-ascii-font-family:"Times New Roman";
mso-hansi-font-family:"Times New Roman"'>条），你可能不得不这样做：</span></p>
<p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p>
<p class=MsoNormal style='margin-left:36.0pt'><span lang=EN-US>inline bool
IsHeavy( const Thing& ) {/*…*/}</span></p>
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