语言-杂谈函数指针

3.4函数指针

函数、应用程序是编译器处理的对象每一个函数模块都有一个首地址，称为函数的入口地址，（函数指针）函数调用：找到函数入口地址；传递参数不带括号的函数名就是函数入口地址

3.4.1 函数的地址inta0x0065FDF40x00401014内存分配……数据对象地址代码对象地址3.4.1函数的地址//例3-20函数和数据的测试#include<iostream.h>voidsimple()

//定义一个简单函数{cout<<"Itisasimpleprogram.\n";}voidmain(){cout<<"Callfunction...\n";simple(); //名方式调用

(&simple)(); //地址方式调用

(*&simple)(); //间址调用

cout<<"Addressoffunction:\n";cout<<simple<<endl;

//函数名是地址

cout<<&simple<<endl; //取函数地址

cout<<*&simple<<endl; //函数地址所指对象

inta=100; //声明一个整数对象

cout<<"Valueofa:\n";cout<<a<<endl;cout<<"Addressofa:\n";cout<<&a<<endl;}3.4.1函数的地址//例3-20函数和数据的测试#include<iostream.h>voidsimple()

//定义一个简单函数{cout<<"Itisasimpleprogram.\n";}voidmain(){cout<<"Callfunction...\n";simple(); //名方式调用

(&simple)(); //地址方式调用

(*&simple)(); //间址调用

cout<<"Addressoffunction:\n";cout<<simple<<endl; //函数名是地址

cout<<&simple<<endl; //取函数地址

cout<<*&simple<<endl; //函数地址所指对象

inta=100; //声明一个整数对象

cout<<"Valueofa:\n";cout<<a<<endl;cout<<"Addressofa:\n";cout<<&a<<endl;}一个无参数的简单函数3.4.1函数的地址//例3-20函数和数据的测试#include<iostream.h>voidsimple()

//定义一个简单函数{cout<<"Itisasimpleprogram.\n";}voidmain(){cout<<"Callfunction...\n";simple(); //名方式调用

(&simple)(); //地址方式调用

(*&simple)(); //间址调用

cout<<"Addressoffunction:\n";cout<<simple<<endl; //函数名是地址

cout<<&simple<<endl; //取函数地址

cout<<*&simple<<endl; //函数地址所指对象

inta=100; //声明一个整数对象

cout<<"Valueofa:\n";cout<<a<<endl;cout<<"Addressofa:\n";cout<<&a<<endl;}3.4.1函数的地址//例3-20函数和数据的测试#include<iostream.h>voidsimple()

//定义一个简单函数{cout<<"Itisasimpleprogram.\n";}voidmain(){cout<<"Callfunction...\n";simple(); //名方式调用

(&simple)();

//地址方式调用

(*&simple)();

//间址调用

cout<<"Addressoffunction:\n";cout<<simple<<endl; //函数名是地址

cout<<&simple<<endl; //取函数地址

cout<<*&simple<<endl; //函数地址所指对象

inta=100; //声明一个整数对象

cout<<"Valueofa:\n";cout<<a<<endl;cout<<"Addressofa:\n";cout<<&a<<endl;}它们都是正确的调用方式3.4.1函数的地址//例3-20函数和数据的测试#include<iostream.h>voidsimple()

//定义一个简单函数{cout<<"Itisasimpleprogram.\n";}voidmain(){cout<<"Callfunction...\n";

simple(); //名方式调用

(&simple)();

//地址方式调用

(*&simple)();

//间址调用

cout<<"Addressoffunction:\n";cout<<

simple

<<endl;

//函数名是地址

cout<<

&simple

<<endl;

//取函数地址

cout<<

*&simple

<<endl; //函数地址所指对象

inta=100; //声明一个整数对象

cout<<"Valueofa:\n";cout<<a<<endl;cout<<"Addressofa:\n";cout<<&a<<endl;}它们都是函数的地址3.4.1函数的地址//例3-20函数和数据的测试#include<iostream.h>voidsimple()

//定义一个简单函数{cout<<"Itisasimpleprogram.\n";}voidmain(){cout<<"Callfunction...\n";simple(); //名方式调用

(&simple)(); //地址方式调用

(*&simple)(); //间址调用

cout<<"Addressoffunction:\n";cout<<simple<<endl; //函数名是地址

cout<<&simple<<endl; //取函数地址

cout<<*&simple<<endl; //函数地址所指对象

inta=100; //声明一个整数对象

cout<<"Valueofa:\n";cout<<a<<endl;cout<<"Addressofa:\n";cout<<&a<<endl;}数据对象的值等价于*&a由类型int解释内存3.4.1函数的地址//例3-20函数和数据的测试#include<iostream.h>voidsimple()

//定义一个简单函数{cout<<"Itisasimpleprogram.\n";}voidmain(){cout<<"Callfunction...\n";simple(); //名方式调用

(&simple)(); //地址方式调用

(*&simple)(); //间址调用

cout<<"Addressoffunction:\n";cout<<simple<<endl; //函数名是地址

cout<<&simple<<endl; //取函数地址

cout<<*&simple<<endl; //函数地址所指对象

inta=100; //声明一个整数对象

cout<<"Valueofa:\n";cout<<a<<endl;cout<<"Addressofa:\n";cout<<&a<<endl;}数据对象的地址3.4.1函数的地址3.4.1 函数的地址C++的函数与数据对象函数FunctionObj数据DataObj地址FunctionObj&FunctionObj*FunctionObj*&FunctionObj&DataObj对象FunctionObj()&FunctionObj()*FunctionObj()*&FunctionObj()DataObj*&DataObj访问调用函数地址表达式

(参数表

)执行代码读：右值表达式写：左值表达式由类型解释数据3.4.1函数的地址3.4.2函数指针

指向函数的指针变量简称为函数指针函数的类型是函数的接口可以通过指针变量的间址方式调用函数3.4.2函数指针3.4.2函数指针1.函数的类型以下是类型相同的函数：

double

max(double,double);

double

min(double,double);

double

average

(double,double);定义函数类型：

typedef

类型

函数类型（形式参数表）；3.4.2函数指针3.4.2函数指针1.函数的类型以下是类型相同的函数：

double

max(double,double);

double

min(double,double);

double

average

(double,double);定义函数类型：

typedef

类型

函数类型（形式参数表）；关键字3.4.2函数指针3.4.2函数指针1.函数的类型以下是类型相同的函数：

double

max(double,double);

double

min(double,double);

double

average

(double,double);定义函数类型：

typedef

类型

函数类型（形式参数表）

；函数返回值类型3.4.2函数指针3.4.2函数指针1.函数的类型以下是类型相同的函数：

double

max(double,double);

double

min(double,double);

double

average

(double,double);定义函数类型：

typedef

类型

函数类型

（形式参数表）；用户定义标识符3.4.2函数指针3.4.2函数指针1.函数的类型以下是类型相同的函数：

double

max(double,double);

double

min(double,double);

double

average

(double,double);定义函数类型：

typedef

类型

函数类型

（形式参数表）

；参数表3.4.2函数指针3.4.2函数指针1.函数的类型以下是类型相同的函数：

double

max(double,double);

double

min(double,double);

double

average

(double,double);它们的类型为：

double

(double,double)

或定义为：

typedef

double

functionType

(double,double);函数类型名3.4.2函数指针3.4.2函数指针2．函数指针若有函数类型为：

double(double,double);或：

typedefdoublefunctionType(double,double);函数指针定义指向这类函数的指针变量：

double(*fp)(double,double);或：

functionType*fp1,*fp2;3.4.2函数指针3.4.2函数指针2．函数指针例如：

doublemax(double,double); doublemin(double,double); doubleaverage(double,double); typedefdoublefunctionType(double,double); functionType*fp1,*fp2; fp1=max; fp2=min; fp1=average; fp1=fp2;3.4.2函数指针3.4.2函数指针2．函数指针例如：

double

max(double,double); doublemin(double,double); doubleaverage(double,double); typedefdoublefunctionType(double,double); functionType*fp1,*fp2; fp1=max; fp2=min; fp1=average; fp1=fp2;函数原型3.4.2函数指针3.4.2函数指针2．函数指针例如：

doublemax(double,double); doublemin(double,double); doubleaverage(double,double);

typedefdoublefunctionType

(double,double); functionType*fp1,*fp2; fp1=max; fp2=min; fp1=average; fp1=fp2;定义函数类型3.4.2函数指针3.4.2函数指针2．函数指针例如：

doublemax(double,double); doublemin(double,double); doubleaverage(double,double); typedefdoublefunctionType(double,double);

functionType*fp1,*fp2; fp1=max; fp2=min; fp1=average; fp1=fp2;声明函数指针3.4.2函数指针3.4.2函数指针2．函数指针例如：

doublemax(double,double); doublemin(double,double); doubleaverage(double,double); typedefdoublefunctionType(double,double); functionType*fp1,*fp2;

fp1=max; fp2=min; fp1=average; fp1=fp2;获取函数地址3.4.2函数指针3.4.2函数指针2．函数指针例如：

doublemax(double,double); doublemin(double,double); doubleaverage(double,double); typedefdoublefunctionType(double,double); functionType*fp1,*fp2; fp1=max; fp2=min; fp1=average;

fp1=fp2;改变指针指向3.4.2函数指针3.4.2函数指针2．函数指针例如：

doublemax(double,double); doublemin(double,double); doubleaverage(double,double); typedefdoublefunctionType(double,double); functionType*fp1,*fp2; fp1=max; fp2=min; fp1=average; fp1=fp2;3.4.2函数指针 typedefdoublefunctionType(double,double); functionTypemax,min,average; 说明了3个函数原型3.4.2函数指针3．用函数指针调用函数例如：

doublemax(double,double); doublemin(double,double); typedefdoublefunctionType(double,double); functionType*fp; fp=max; doublex=fp(3.14,0.516); fp=min; cout<<fp(0.75,x)<<endl; 3.4.2函数指针3.4.2函数指针3．用函数指针调用函数例如：

doublemax(double,double); doublemin(double,double); typedefdoublefunctionType(double,double); functionType*fp;

fp=max; doublex=fp(3.14,0.516); fp=min; cout<<fp(0.75,x)<<endl; 指向函数max3.4.2函数指针//例3-21用函数指针调用函数#include<iostream.h>intsum(intx,inty){returnx+y;}intproduct(intx,inty){returnx*y;}voidmain(){int(*pf)(int,int);inta,b,result;cout<<"a="; cin>>a;cout<<"b="; cin>>b;pf=sum;result=pf(a,b);cout<<a<<"+"<<b<<"="<<result<<endl;pf=product;result=pf(a,b);cout<<a<<"*"<<b<<"="<<result<<endl;}3.4.2函数指针3.4.2函数指针//例3-21用函数指针调用函数#include<iostream.h>intsum(intx,inty){returnx+y;}intproduct(intx,inty){returnx*y;}voidmain(){

int(*pf)(int,int);

inta,b,result;cout<<"a="; cin>>a;cout<<"b="; cin>>b;pf=sum;result=pf(a,b);cout<<a<<"+"<<b<<"="<<result<<endl;pf=product;result=pf(a,b);cout<<a<<"*"<<b<<"="<<result<<endl;}3.4.2函数指针函数指针3.4.2函数指针//例3-21用函数指针调用函数#include<iostream.h>intsum(intx,inty){returnx+y;}intproduct(intx,inty){returnx*y;}voidmain(){int(*pf)(int,int);inta,b,result;cout<<"a="; cin>>a;cout<<"b="; cin>>b;

pf=sum

;result=

pf(a,b)

;cout<<a<<"+"<<b<<"="<<result<<endl;

pf=product

;result=

pf(a,b)

;cout<<a<<"*"<<b<<"="<<result<<endl;}3.4.2函数指针调用不同函数3.4.2函数指针//例3-21用函数指针调用函数#include<iostream.h>intsum(intx,inty){returnx+y;}intproduct(intx,inty){returnx*y;}voidmain(){int(*pf)(int,int);inta,b,result;cout<<"a="; cin>>a;cout<<"b="; cin>>b;

pf=sum

;result=

pf(a,b)

;cout<<a<<"+"<<b<<"="<<result<<endl;

pf=product

;result=

pf(a,b)

;cout<<a<<"*"<<b<<"="<<result<<endl;}3.4.2函数指针(*pf)(a,b)等价吗？3.4.2函数指针//例3-21用函数指针调用函数#include<iostream.h>intsum(intx,inty){returnx+y;}intproduct(intx,inty){returnx*y;}voidmain(){int(*pf)(int,int);inta,b,result;cout<<"a="; cin>>a;cout<<"b="; cin>>b;

pf=sum

;result=

pf(a,b

)

;cout<<a<<"+"<<b<<"="<<result<<endl;

pf=product

;result=

pf(a,b)

;cout<<a<<"*"<<b<<"="<<result<<endl;}3.4.2函数指针(&pf)(a,b)等价吗？3.4.2函数指针//例3-21用函数指针调用函数#include<iostream.h>intsum(intx,inty){returnx+y;}intproduct(intx,inty){returnx*y;}voidmain(){int(*pf)(int,int);inta,b,result;cout<<"a="; cin>>a;cout<<"b="; cin>>b;

pf=sum

;result=

pf(a,b

)

;cout<<a<<"+"<<b<<"="<<result<<endl;

pf=product

;result=

pf(a,b)

;cout<<a<<"*"<<b<<"="<<result<<endl;}3.4.2函数指针(&pf)(a,b)与

(&sum)(a,b)

有何区别?3.4.2函数指针//例3-21用函数指针调用函数#include<iostream.h>intsum(intx,inty){returnx+y;}intproduct(intx,inty){returnx*y;}voidmain(){int(*pf)(int,int);inta,b,result;cout<<"a="; cin>>a;cout<<"b="; cin>>b;

pf=sum

;result=

pf(a,b

)

;cout<<a<<"+"<<b<<"="<<result<<endl;

pf=product

;result=

pf(a,b)

;cout<<a<<"*"<<b<<"="<<result<<endl;}3.4.2函数指针pf

是指针变量，存放函数的地址sum是函数的直接地址pf的值等于sum（

&sum）&pf不等于sum（&sum）3.4.2函数指针//例3-22使用函数指针参数调用函数

#include<iostream.h>#include<math.h>typedefdoublefunType(double); //定义函数类型funTypecirclePerimeter; //用函数类型名定义函数原型funTypecircleArea;funTypeballArea;funTypeballVolume;doublecallFun(funType*,double); //第一个参数是函数指针参数voidmain(){doubler;cout<<"entertheradius:";cin>>r;cout<<"theperimeterofcircleis:"<<callFun(circlePerimeter,r)<<endl;cout<<"theareaofcircleis:"<<callFun(circleArea,r)<<endl;cout<<"entertheradiusofaball:";cin>>r;cout<<"theareaoftheballis:"<<callFun(ballArea,r)<<endl;cout<<"thevolumeoftheballis:"<<callFun(ballVolume,r)<<endl;}3.4.2函数指针//例3-22使用函数指针参数调用函数

#include<iostream.h>#include<math.h>typedefdoublefunType(double); //定义函数类型funTypecirclePerimeter; //用函数类型名定义函数原型funTypecircleArea;funTypeballArea;funTypeballVolume;doublecallFun(funType*,double); //第一个参数是函数指针参数voidmain(){doubler;cout<<"entertheradius:";cin>>r;cout<<"theperimeterofcircleis:"<<callFun(circlePerimeter,r)<<endl;cout<<"theareaofcircleis:"<<callFun(circleArea,r)<<endl;cout<<"entertheradiusofaball:";cin>>r;cout<<"theareaoftheballis:"<<callFun(ballArea,r)<<endl;cout<<"thevolumeoftheballis:"<<callFun(ballVolume,r)<<endl;}函数类型3.4.2函数指针//例3-22使用函数指针参数调用函数#include<iostream.h>#include<math.h>typedefdoublefunType(double); //定义函数类型funTypecirclePerimeter;

//用函数类型名定义函数原型funTypecircleArea;funTypeballArea;funTypeballVolume;doublecallFun(funType*,double); //第一个参数是函数指针参数voidmain(){doubler;cout<<"entertheradius:";cin>>r;cout<<"theperimeterofcircleis:"<<callFun(circlePerimeter,r)<<endl;cout<<"theareaofcircleis:"<<callFun(circleArea,r)<<endl;cout<<"entertheradiusofaball:";cin>>r;cout<<"theareaoftheballis:"<<callFun(ballArea,r)<<endl;cout<<"thevolumeoftheballis:"<<callFun(ballVolume,r)<<endl;}函数原型doublecirclePerimeter(double);doublecircleArea(double);doubleballArea(double);doubleballVolume(double);3.4.2函数指针//例3-22使用函数指针参数调用函数#include<iostream.h>#include<math.h>typedefdoublefunType(double); //定义函数类型funTypecirclePerimeter; //用函数类型名定义函数原型funTypecircleArea;funTypeballArea;funTypeballVolume;doublecallFun(funType*,double);

//第一个参数是函数指针参数voidmain(){doubler;cout<<"entertheradius:";cin>>r;cout<<"theperimeterofcircleis:"<<callFun(circlePerimeter,r)<<endl;cout<<"theareaofcircleis:"<<callFun(circleArea,r)<<endl;cout<<"entertheradiusofaball:";cin>>r;cout<<"theareaoftheballis:"<<callFun(ballArea,r)<<endl;cout<<"thevolumeoftheballis:"<<callFun(ballVolume,r)<<endl;}函数原型3.4.2函数指针//例3-22使用函数指针参数调用函数#include<iostream.h>#include<math.h>typedefdoublefunType(double); //定义函数类型funTypecirclePerimeter; //用函数类型名定义函数原型funTypecircleArea;funTypeballArea;funTypeballVolume;doublecallFun(funType*,double);

//第一个参数是函数指针参数voidmain(){doubler;cout<<"entertheradius:";cin>>r;cout<<"theperimeterofcircleis:"<<callFun(circlePerimeter,r)<<endl;cout<<"theareaofcircleis:"<<callFun(circleArea,r)<<endl;cout<<"entertheradiusofaball:";cin>>r;cout<<"theareaoftheballis:"<<callFun(ballArea,r)<<endl;cout<<"thevolumeoftheballis:"<<callFun(ballVolume,r)<<endl;}函数指针参数double(*)(double)3.4.2函数指针//例3-22使用函数指针参数调用函数#include<iostream.h>#include<math.h>typedefdoublefunType(double); //定义函数类型funTypecirclePerimeter; //用函数类型名定义函数原型funTypecircleArea;funTypeballArea;funTypeballVolume;doublecallFun(funType*,double); //第一个参数是函数指针参数voidmain(){doubler;cout<<"entertheradius:";cin>>r;cout<<"theperimeterofcircleis:"<<callFun(circlePerimeter,r)<<endl;cout<<"theareaofcircleis:"<<callFun(circleArea,r)<<endl;cout<<"entertheradiusofaball:";cin>>r;cout<<"theareaoftheballis:"<<callFun(ballArea,r)<<endl;cout<<"thevolumeoftheballis:"<<callFun(ballVolume,r)<<endl;}实际参数是函数地址3.4.2函数指针voidmain(){doubler;cout<<"entertheradius:";cin>>r;cout<<"theperimeterofcircleis:"<<callFun(circlePerimeter,r)<<endl;cout<<"theareaofcircleis:"<<callFun(circleArea,r)<<endl;cout<<"entertheradiusofaball:";cin>>r;cout<<"theareaoftheballis:"<<callFun(ballArea,r)<<endl;cout<<"thevolumeoftheballis:"<<callFun(ballVolume,r)<<endl;}constdoublepi=3.14159;doublecallFun(funType*qf,doubler){returnqf(r);}doublecirclePerimeter(doubleradius){return2*pi*radius;}doublecircleArea(doubleradius){returnpi*radius*radius;}doubleballArea(doubleradius){return4*pi*radius*radius;}doubleballVolume(doubleradius){return4.0/3*pi*pow(radius,3);}circlePerimeter(r)3.4.2函数指针voidmain(){doubler;cout<<"entertheradius:";cin>>r;cout<<"theperimeterofcircleis:"<<callFun(circlePerimeter,r)<<endl;cout<<"theareaofcircleis:"<<callFun(circleArea,r)<<endl;cout<<"entertheradiusofaball:";cin>>r;cout<<"theareaoftheballis:"<<callFun(ballArea,r)<<endl;cout<<"thevolumeoftheballis:"<<callFun(ballVolume,r)<<endl;}constdoublepi=3.14159;doublecallFun(funType*qf,doubler){returnqf(r);}doublecirclePerimeter(doubleradius){return2*pi*radius;}doublecircleArea(doubleradius){returnpi*radius*radius;}doubleballArea(doubleradius){return4*pi*radius*radius;}doubleballVolume(doubleradius){return4.0/3*pi*pow(radius,3);}circlePerimeter(r)3.4.2函数指针voidmain(){doubler;cout<<"entertheradius:";cin>>r;cout<<"theperimeterofcircleis:"<<callFun(circlePerimeter,r)<<endl;cout<<"theareaofcircleis:"<<callFun(circleArea,r)<<endl;cout<<"entertheradiusofaball:";cin>>r;cout<<"theareaoftheballis:"<<callFun(ballArea,r)<<endl;cout<<"thevolumeoftheballis:"<<callFun(ballVolume,r)<<endl;}constdoublepi=3.14159;doublecallFun(funType*qf,doubler){returnqf(r);}doublecirclePerimeter(doubleradius){return2*pi*radius;}doublecircleArea(doubleradius){returnpi*radius*radius;}doubleballArea(doubleradius){return4*pi*radius*radius;}doubleballVolume(doubleradius){return4.0/3*pi*pow(radius,3);}circleArea(r)3.4.2函数指针voidmain(){doubler;cout<<"entertheradius:";cin>>r;cout<<"theperimeterofcircleis:"<<callFun(circlePerimeter,r)<<endl;cout<<"theareaofcircleis:"<<callFun(circleArea,r)<<endl;cout<<"entertheradiusofaball:";cin>>r;cout<<"theareaoftheballis:"<<callFun(ballArea,r)<<endl;cout<<"thevolumeoftheballis:"<<callFun(ballVolume,r)<<endl;}constdoublepi=3.14159;doublecallFun(funType*qf,doubler){returnqf(r);}doublecirclePerimeter(doubleradius){return2*pi*radius;}doublecircleArea(doubleradius){returnpi*radius*radius;}doubleballArea(doubleradius){return4*pi*radius*radius;}doubleballVolume(doubleradius){return4.0/3*pi*pow(radius,3);}circleArea(r)3.4.2函数指针voidmain(){doubler;cout<<"entertheradius:";cin>>r;cout<<"theperimeterofcircleis:"<<callFun(circlePerimeter,r)<<endl;cout<<"theareaofcircleis:"<<callFun(circleArea,r)<<endl;cout<<"entertheradiusofaball:";cin>>r;cout<<"theareaoftheballis:"<<callFun(ballArea,r)<<endl;cout<<"thevolumeoftheballis:"<<callFun(ballVolume,r)<<endl;}constdoublepi=3.14159;doublecallFun(funType*qf,doubler){returnqf(r);}doublecirclePerimeter(doubleradius){return2*pi*radius;}doublecircleArea(doubleradius){returnpi*radius*radius;}doubleballArea(doubleradius){return4*pi*radius*radius;}doubleballVolume(doubleradius){return4.0/3*pi*pow(radius,3);}ballArea(r)3.4.2函数指针voidmain(){doubler;cout<<"entertheradius:";cin>>r;cout<<"theperimeterofcircleis:"<<callFun(circlePerimeter,r)<<endl;cout<<"theareaofcircleis:"<<callFun(circleArea,r)<<endl;cout<<"entertheradiusofaball:";cin>>r;cout<<"theareaoftheballis:"<<callFun(ballArea,r)<<endl;cout<<"thevolumeoftheballis:"<<callFun(ballVolume,r)<<endl;}constdoublepi=3.14159;doublecallFun(funType*qf,doubler){returnqf(r);}doublecirclePerimeter(doubleradius){return2*pi*radius;}doublecircleArea(doubleradius){returnpi*radius*radius;}doubleballArea(doubleradius){return4*pi*radius*radius;}doubleballVolume(doubleradius){return4.0/3*pi*pow(radius,3);}ballArea(r)3.4.2函数指针vo