第三章函数(Functions)3.1Introduction3.2C++程序组件(ProgramComponentsinC++)FunctionsinvokedbyfunctioncallFunctionnameandinformation(arguments)itneedsFunctiondefinitionsOnlywrittenonceHiddenfromotherfunctionsBosstoworkeranalogy(类似)-Aboss(thecallingfunctionorcaller)asksaworker(thecalledfunction)toperformataskandreturn(i.e.,reportback)theresultswhenthetaskisdone.软件工程知识01：利用在线文档熟悉C++标准库中的函数和类的集合。3.3MathLibraryFunctionsFunctionargumentscanbe-Constantssqrt(4);-Variablessqrt(x);-Expressionssqrt(sqrt(x));sqrt(3-6x);3.4Functions软件工程知识03：在包含许多函数的程序中，main应被视为一组函数调用，而这组函数用于执行程序的大部分工作。3.5FunctionDefinitionsFormatforfunctiondefinitionreturn-value-typefunction-name(parameter-list){declarationsandstatements}-ParameterlistCommaseparatedlistofarguments-DatatypeneededforeachargumentIfnoargumentsareneeded,usevoidorleaveblank-Return-value-typeDatatypeofresultreturned(usevoidifnothingreturned)Examplefunctionintsquare(inty){returny*y;}returnkeywordReturnsdata,andcontrolgoestofunction’scallerIfnodatatoreturn,usereturn;FunctionendswhenreachesrightbraceFunctionscannotbedefinedinsideotherfunctions1//Fig.3.3:fig03_03.cpp2//Creatingandusingaprogrammer-definedfunction.3#include<iostream>45usingstd::cout;6usingstd::endl;78intsquare(int);//functionprototype910intmain()11{12//loop10timesandcalculateandoutput13//squareofxeachtime14for(intx=1;x<=10;x++)15cout<<square(x)<<"";//functioncall1617cout<<endl;1819return0;//indicatessuccessfultermination2021}//endmain2223//squarefunctiondefinitionreturnssquareofaninteger24intsquare(inty)//yisacopyofargumenttofunction25{26returny*y;//returnssquareofyasanint2728}//endfunctionsquare1//Fig.3.4:fig03_04.cpp2//Findingthemaximumofthreefloating-pointnumbers.3#include<iostream>45usingstd::cout;6usingstd::cin;7usingstd::endl;89doublemaximum(double,double,double);//functionprototype1011intmain()12{13doublenumber1;14doublenumber2;15doublenumber3;1617cout<<"Enterthreefloating-pointnumbers:";18cin>>n