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C++ Primer 读书笔记 - 第七章
添加时间:2013-5-26 点击量:1. To invoke a function we use the call operator， which is a pair of parentheses. The operands to the call operator are the name of the function and a （possibly empty） comma-separated list of arguments.
＃include <iostream>
using namespace std;
string::size_type find_char（const string &s， char c）
{
string::size_type i = 0;
while （i != s.size（） && s[i] != c）
++i;
return i;
}
bool is_sentence（const string &s）
{
return （find_char（s， .） == s.size（） - 1）;
}
int add（const int &i）
{
return （i + 1）;
}
int main（）
{
cout << （is_sentence（abc） ？ YES : NO） << endl;
cout << add（8） << endl;
int a[] = {1， 2， 3， 4， 5， 6};
return 0;
}2. A function may not return another function or a built-in array type.
＃include <iostream>
using namespace std;
//It is wrong to return built-in array type
int[] return_arr（）
{
int arr[] = {1，2，3};
return arr;
}
int main（）
{
int b[] = return_arr（）;
return 0;
}3. The compiler treats
void fcn（const int i）;
void fcn（int i）;as the same.
f（int ）
f（int const）also treated as the same.
Because the parameter is a copy of the passed value.
4. In C++ it is safer and more natural to use reference parameters. A reference must be initialized using an object of the same type as the reference. A nonconst reference may be bound only to nonconst object of exactly the same type.
5. There are three common programming techniques to ensure that a function stays within the bounds of its array arguments.
Place a marker as the end of the array.
C-style void fun（int a， int len） //len is the length of the array
C++ style void func（int begin， int end）
6. array as the parameter
void pirntValues（int ） //this is commonly used
void printValues（int []）
void printValues（int [10]） //10 is meaningless
void printValues（int （&arr）[10]） //parameter is a reference to an array; size of array is fixed
//for multidimensional array
void foo（int （matrix）[10]） //10 must be specified
int matrix[10] // array of 10 pointers7. When a function returns a reference type， the return value is not copied. Instead， the object itself is returned.
Reference returns are lvalues
It may be surprising to assign to the return of a function， but the return is a reference. As such， it is just a synonym for the element returned.
＃include <iostream>
using namespace std;
int &larger（int &a， int &b）
{
return a > b ？ a : b;
}
int main（）
{
int a = 4;
int b = 5;
cout << larger（a， b） << endl;
larger（a， b） = 10;
cout << a = << a << \tb = << b << endl;
return 0;
}
//output:
//5
//a = 4 b = 108. Put inline functions in header files. They should be defined in header files.
9. Whenever an inline function is added to or changed in a header file， every source file that uses that header must be recompiled.
So we should be careful when we write Makefile.
10. Const member function -> The object which invokes this function will not be changed.
11. Default constructor
class Sales_item {
public:
double avg_price（） const;
bool same_isbn（const Sales_item &rhs） const //A member function that is defined inside the class is implicitly treated as an inline function
{ return isbn == rhs.isbn; }
Sales_item（）: units_sold（0）， revenue（0） { } //as isbn is string， it has its own default constructor， it will initialized as
private:
std::string isbn;
unsigned units_sold;
double revenue;
};12. Overloaded Functions -> Same name， different parameters.
Although we cannot pass an integral value to a enum parameter， we can pass an enum to a parameter of integral type.
13. typedef bool （comFcn） （const string &， const string &）;
14. Returning a pointer to function.
int （ff（int）） （int ， int）;
ff（int） is a function returns int （）（int ， int）;
//use typedef
typedef int （PF）（int ， int）;
PF ff（int）; //ff returns a pointer to function
容易发怒的意思就是： 别人做了蠢事， 然后我们代替他们， 表现出笨蛋的样子。—— 蔡康永
