C++ primer plus Chapter 7 and Chapter 8

Chapter 7 1
Chapter 7 2
Chapter 7 Review
Chapter 8 1
Chapter 8 2
Chapter 8 3
To use C++ functions, you must complete the following tasks:

Provide function definition
Provide function prototype
Call functions

How the function returns a value

The function returns the return value by copying it to the specified CPU register or memory unit, and then calls the program to view the memory unit. The return function and the calling function must agree on the type of data stored in the memory unit, and the function prototype will The return value type tells the calling program, and the function defines what type of data the called function should return
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Function prototype

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The prototype (prototype) describes the interface of the function to the compiler, that is, it tells the compiler the type and number of the return value of the function and the type and number of parameters. The
function prototype is a statement, so it must end with a semicolon.
For example:

double cube(double x);

Variable names can be included or not included in the function prototype

Functions and arrays

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Functions and two-dimensional arrays

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int (*ar2)[4];  //声明一个指向由4个int组成的数组的指针
int *ar2[4];    //声明一个由4个指向int的指针构成的数组

Function and structure

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Transfer structure address

Recursion

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Recursion with multiple calls

Function pointer

Get function address

Just use the function name (without parameters). For
example: think() is a function, process(), thought() are both functions
process(think) // Pass the address of the think function to the process function
thought( think ()) // Pass the return value of the think function to the thought function

Declare function pointer

double pam(int);   //函数原型，声明了一个 叫做 pam的函数
下面的语句和上面的语句效果是相同的
double (*pf)(int);   // pf就是函数指针

double (*pf)(int);   //pf points to a function that returns double
double *pf(int);     //pf() is  a function that returns a pointer-to-double

double pam(int);
double (*pf)(int);
pf = pam;

void estimate(int a,double pam);
void estimate(int a,double (*pf)(int));

Use a pointer to call a function

double pam(int);
double (*pf)(int);
pf = pam;
double x = pam(4);
double y = (*pf)(5);
double z = pf(6);

* Currently, in C++, it is considered that ( pf)() and pf() and pam() these three function call methods are the same