Accelerated C++：通过示例进行编程实践——练习解答（第12章）
我的Github地址：https://github.com/lanbeilyj/Accerlerated-C-plus-plus
最后章节综合度较大，一些相关习题也综合在一起了。
12-0. Compile, execute, and test the programs in this chapter.
Ans：见Github。
12-1. Reimplement the Str class, but choose an implementation strategy that requires that the class manage the storage itself. For example, you might store an array ofchar and a length. Consider what implications this change in design has for copy control. Also consider the cost of usingVec, (e.g., in storage overhead).
Ans：见Github。
12-2. Implement the c_str, data, and copy functions.
Ans：见Github。
12-3. Define the relational operators for Str. In doing so, you will want to know that the<cstring> header defines a function calledstrcmp, which compares two character pointers. The function returns a negative integer if the null-terminated character array denoted by the first pointer is less than the second, zero if the two strings are equal, or a positive value if the first string is greater than the second.
Ans：见Github。
12-4. Define the equality and inequality operators for Str.
Ans：见Github。
12-5. Implement concatenation for Str so as not to rely on conversions fromconst char*.
Ans：见Github。
12-6. Give Str an operation that will let us implicitly use aStr object as a condition. The test should fail if theStr is empty, and should succeed otherwise.
Ans：见Github。
12-7. The standard string class provides random-access iterators to manipulate thestring's characters. Add iterators and the iterator operations begin and end to yourStr class.
Ans：见Github。
12-8. Add the getline function to the Str class.
Ans：见Github。
12-9. Use class ostream_iterator to reimplement theStr output operator. Why didn't we ask you to reimplement the input operator using classistream_iterator?
Ans：见Github。
12-10. Having seen in §12.1/212 how Str defined a constructor that takes a pair of iterators, we can imagine that such a constructor would be useful in classVec. Add this constructor toVec, and reimplement Str to use the Vec constructor instead of callingcopy.
Ans：见Github。
12-11. If you add the operations listed in these exercises, then you can use thisStr class in all the examples in this book. Reimplement the operations on character pictures from Chapter 5 and thesplit functions from §5.6/87 and §6.1.1/103.
Ans：见Github。
12-12. Define the insert function that takes two iterators for theVec andStr classes.
Ans：见Github。
12-13. Provide an assign function that could be used to assign the values in an array to aVec.
Ans：见Github。
12-14. Write a program to initialize a Vec from astring.
Ans：见Github。
12-15. The read_hw function from §4.1.3/57 checked the stream from which it read to determine whether the function had hit end-of-file, or had encountered an invalid input. OurStr input operator does no such check. Why? Will it leave the stream in an invalid state?
Ans：4.1.3中因为需要从流中读取每个学生的所有家庭作业成绩，因而需要判断，当一个学生的所有homework输入完成后流会变成无效状态，此时需要清除流状态以使流对下一个学生有效；若不判断则则只能对一个学生的成绩进行处理。在本章的Str中没有判断，是我们从流中逐个读取一个字符并判断，流会处于无效状态。
std::istream& operator>> (std::istream& is,Str& s)
{
s.data.clear();
char c;
while(is.get(c) && isspace(c));
if(is)
{
do
{
s.data.push_back(c);
}while(is.get(c) && !isspace(c));
if(is)
is.unget();
}
return is;
}
4.1.3
istream& read_hw(istream& is,vector<double>& hw)
{
if(is)
{
hw.clear();
double x;
while(is>>x)
hw.push_back(x);
is.clear();
}
return is;
}