August 2021
Intermediate to advanced
450 pages
9h 36m
Chinese
Content preview from C++程序设计：原理与实践（基础篇）（原书第2版）
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7.6.2 使用函数
程序中所使用的函数应该反映出该程序的基本结构，而函数名则应有效地标识代码的逻辑独立部分。到目前为止，计算器程序在这些方面做得还是比较好的：expression（）、term（）和primary（）直接反映出我们对表达式文法的理解，而函数get（）则用来处理表达式输入和单词识别。分析一下主函数main（），我们注意到它主要做了两项逻辑上相互独立的任务。
1.main（）函数搭起了程序的整体框架：启动程序、结束程序、处理致命错误。
2.main（）函数用一个循环来计算表达式。
理想情况下，一个函数只实现一个独立的逻辑功能（参见4.5.1节）。而main（）实现了两个功能，这使得程序结构变得有些模糊。一种显然的改进方法是将表达式计算循环从主函数中分离出来，实现为calculate（）函数：
修改后的代码更直接地反映了程序的结构，更易于理解。
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