C++面向对象程序设计双语教程（第3版）课件 class 2-basic facilities-1

ObjectivesTobeabletoconstructasimpleC++programTo

beabletobefamiliarwithinput/outputstreamToknowhowtouseC++constantsTounderstandhowtoconstructprogramsmodularlybyusingfunctions(data

abstraction)01C++ProgramStructure03Constants02Input/OutputStream04Functions01C++ProgramStructureABriefDescriptionofC++C++isageneral-purposeprogramminglanguagewithadvantagestowardsthesystemprogrammingthatisabetterCsupportsdataabstractionsupportsstructuredprogrammingsupportsobject-orientedprogrammingsupportsgenericprogrammingC++ProgramStructureProblem:Writeaprogramforagradebookofagivencourse.Thegradebookincludescourse’sname,hourandlecturer,aswellasstudent’sID,nameandgradeInputallinformationoncourseandstudent;Calculatetheaveragegradeofthecourse;Printthegradebook.CaseStudy1Requirements:C++ProgramStructureDataToacourse,name,hourandlecturer,averagegrade;Tomanystudents,ID,nameandgrade;2.Datatypesname,lecturer-string(char*),grade-int,average-float3.Outputagradebookhavingacoursename,hourandlecturer,manystudents’ID,nameandgrade,

and

course

average

grade.4.Procedures(algorithm)InputalldataincludeacourseandstudentsCalculateaveragegradePrintagradebookProblem-solvingIDNameGrade200405XXXwang89………average70.67Name:OOPHour:48Lecturer:LIUJMGradeBookofOOPC++ProgramStructuremainsetCoursesetStudentaverageGradeprintCourseprintStudentGradeprintGradeBookinputStructuredprogrammingC++ProgramStructure////////////////////////////////////////////////////////////////////////gradebook.cpp//Theprogramreadscourseinformationandstudents'gradefromthe//console,calculatestheaveragegradeandoutputsstudents'grades.//////////////////////////////////////////////////////////////////////#include

<iostream>#include

<string>#include

<iomanip>using

namespacestd;//declarationofconstantsconst

intstudentNum=5;//declarationofinputfunctionsvoidsetCourseInfo(string&cName,string&lectName,int&cHour);voidsetGrade(int(&sNo)[studentNum],string(&sName)[studentNum],

int(&g)[studentNum]);doubleaverage(int

g[]);//declarationofoutputfunctionsvoidprintCourseInfor(string,string,int);voidprintGradeBook(int*,string*,int*);intmain(){stringcourseName;stringlecturer;intcourseHour;intstudentNo[studentNum];stringstudentName[studentNum];intgrade[studentNum];//ReadthecourseandstudentdatasetCourseInfo(courseName,lecturer,courseHour);setGrade(studentNo,studentName,grade);//DisplaythecourseandstudentdataprintCourseInfor(courseName,lecturer,courseHour);printGradeBook(studentNo,studentName,grade);return0;}C++ProgramStructuredoubleaverage(int

g[]){intsum=0;for(inti=0;i<studentNum;i++) sum+=g[i];return

static_cast<double>(sum)/studentNum;}C++ProgramStructure//ReadthecourseandstudentdatavoidsetCourseInfo(string&cName,string&lectName,int&cHour){cout<<"EntercourseInformation\n";cin>>cName>>lectName>>cHour;}voidsetGrade(int(&sNo)[studentNum],string(&sName)[studentNum],

int(&g)[studentNum]){cout<<"Enterstudent'sgrades\n";for(inti=0;i<studentNum;i++){sNo[i]=i;cin>>sName[i]>>g[i];}}C++ProgramStructurevoidprintCourseInfor(string

cName,string

lectName,int

cHour){cout<<"Coursename:"<<cName

<<"Coursehour:"<<cHour

<<"Lecturer:"<<lectName<<endl;}voidprintGradeBook(int*sNo,string*sName,int*sg){cout<<"----------------------------\n";cout<<"StudentNoNameGrade\n";for(inti=0;i<studentNum;i++)cout<<setw(9)<<right<<sNo[i]<<setw(10)<<sName[i]<<setw(7)<<right<<sg[i]<<endl;cout<<"----------------------------\n";cout<<"Theaveragegrade:"<<average(sg)<<endl;}C++ProgramStructureAcommonstructureofsimple,onefile,C++programsCommentsdescribe

theprogram,name,…Includestatementsspecifytheheaderfilesforlibraries.//gradebook.cpp//Theprogramreadscourseinformation…Usingnamespacestatement.#include<iostream>usingnamespacestd;LinecommentsBlockcommentsGlobaldeclarations(consts,types,variables,...).const

intstudenNum=5;Functionprototypes(declarations)voidprintGradeBook(int*,string*,int*);The

mainfunctiondefinitionintmain(){stringcourseName;stringlecturer;intcourseHour;intstudentNo[studentNum];stringstudentName[studentNum];intgrade[studentNum];//ReadthecourseandstudentdatasetCourseInfo(courseName,lecturer,courseHour);setGrade(studentNo,studentName,grade);……}C++ProgramStructureFunctiondefinitionsdoubleaverage(int

g[]){intsum=0;for(inti=0;i<studentNum;i++) sum+=g[i];return

static_cast<double>(sum)/studentNum;}02Input/Output

Stream//ReadthestudentdatavoidsetGrade(int(&sNo)[studentNum],string(&sName)[studentNum],

int(&g)[studentNum]){cout<<"Enterstudent'sgrades\n";for(inti=0;i<studentNum;i++){sNo[i]=i;cin>>sName[i]>>g[i];}}Input/OutputStreamOutputstreamInputstreamTheiostreamlibrarydefinesinput/outputforeverybuilt-intype.#include<iostream>Input/OutputStreamAstream

isasequenceofcharactersfromthesourcetothedestination.Therearetwotypesofstreams:Inputstream:Asequenceofcharactersfromaninputdevice(keyboard)tothecomputer(variables).Outputstream:Asequenceofcharactersfromthecomputer(variables)toanoutputdevice(screen).Input/OutputStreamTheextractionoperator(>>)isusedasaninputoperator.Inputstreamisfromthedevicetovariables.Keyword

cinisthestandardinputstream.Theinsertionoperator(<<)isusedasoutputoperator.Outputstreamisfromvariablestothedevice.Keyword

coutisthestandardoutputstream.cin>>courseName>>courseHour>>lecturer;

cout<<“Coursename:“<<courseName<<endl;ConsoleinputConsoleoutput//ReadthestudentdatavoidsetGrade(int(&sNo)[studentNum],string(&sName)[studentNum],int(&g)[studentNum]){cout<<"Enterstudent'sgrades\n";for(inti=0;i<studentNum;i++){sNo[i]=i;cin>>sName[i]>>g[i];}}Input/OutputstreamOutputstream(printf)Inputstream(scanf)03ConstantsConstantsTheconst

keywordmeansthatavaluedoesnotchangedirectly.Aconstantmustbeinitialized.#include

<iostream>#include

<string>#include

<iomanip>using

namespacestd;//declarationofconstantsconst

intstudentNum=5;A#defineisamacrowhichreplacesthemacro-namewithauser-definedtextstatement.Aconstidentifierallowsavariabletobeconstantthroughoutthefile.Constantsconstintmodel=90;constintv[]={1,2,3,4};constintx;intmain(){model=200;v[2]++;}Example//error–cannotbechanged//error–cannotbechanged//error-don’tinitializevoidf(){charstr[]="hello";char*str1=str;const

char*p1=str;//valueisconstant//p1[2]='w';//errorp1=str1;char*constp2=str;//addressisconstantp2[2]='w';//p2=str1;//errorconst

char*constp3=str;//p3[2]='w';//error//p3=str1;//error}04FunctionsFunctionsintmain(){stringcourseName;stringlecturer;intcourseHour;intstudentNo[studentNum];stringstudentName[studentNum];intgrade[studentNum];//ReadthecourseandstudentdatasetCourseInfo(courseName,lecturer,courseHour);setGrade(studentNo,studentName,grade);//DisplaythecourseandstudentdataprintCourseInfor(courseName,lecturer,courseHour);printGradeBook(studentNo,studentName,grade);return0;}Functions:programisbrief.easilymaintainenhancetheefficiencyofprogrammingreusableWhytousefunctions?Thefunctionalfeaturesofaprogramcanbesubdividedintoblocksofcodeknownas

functions.intmain(){…….setCourseInfo(courseName,lecturer,courseHour);}voidsetCourseInfo(string&cName,string&lectName,int&cHour){cout<<"EntercourseInformation\n";cin>>cName>>lectName>>cHour;}voidsetCourseInfo(string&cName,string&lectName,int&cHour);DeclarationandDefinitionofFunctionsAdeclarationestablishesthenameofthefunction,thetypeofreturnedbythefunction,theparameternumbersandtypesoftheparameterlist.declaration-prototypeFunctionbodyFunctiondefinitionFunctioncallHowtousefunctions?FunctionsignatureFunctionheaderFunctionswithDefaultArguments/ParametersProblem:Inquireastudent’sgradeinwhichispassorfail.intmain(){setCourseInfo(courseName,lecturer,courseHour);setGrade(studentNo,studentName,grade);inttempNo;cout<<"Inquireastudent'sgrade.EnterastudentID\n";cin>>tempNo;cout<<gradeResult(grade[tempNo])<<endl;return0;}chargradeResult(int,int=60);DefaultparameterchargradeResult(int

gradeOne,int

passValue){if(gradeOne>=passValue) return

'P';else return

'F';}DefaultargumentCaseStudy1-1FunctionswithDefaultParametersA

defaultparameterisafunctionparameter

thathasadefaultvalueprovidedtoit.chargradeResult(int,int=60);Adefaultparameteristypecheckedatthe

timeofthefunctiondeclarationandevaluatedatthetimeofthecall.(1)Iftheuserdoesnotsupplyavalueforthisparameter,thedefaultvaluewillbeused;(2)Iftheuserdoessupplyavalueforthedefaultparameter,theuser-suppliedvalueisusedinsteadofthedefaultvalue.FunctionswithDefaultParametersvoidprint(intval1=10,intval2=20,intval3=30);intmain(){print();print(31);print(31,10);print(31,16,15);}voidprint(intval1,intval2,intval3){cout<<val1<<val2<<val3<<endl;}Result:102030312030311030311615definitionFunctioncallWhentherecanexistmorethanoneparameterintheparameterlist,forexample,declarationLeftmostcriteria:fromlefttorightFunctionswithDefaultParametersvoidprint(intval1=10,intval2=20,intval3);voidprint(intval1=10,intval2,intval3=30);

voidprint(intval1,intval2=0,intval3=0);//error//error//okAlldefaultparameterswithindeclarationordefinitionmustbetherightmostparameters.Rightmostcriteria:fromrighttoleftFunction

OverloadingProblem:OutputthegradebookwithstudentIDandgrade.Twoormorefunctionshavethesamenameinthesamescopeiscalledfunctionoverloading.voidprintGradeBook(int*sNo,string*sName,int*sg);voidprintGradeBook(intsNo[],intg[]);C++allowsyoutospecifytwoormoredefinitionsfora

function

name

inthesamescope.Thecompilerwillneedtodeterminewhichfunctiontoexecutebasedonthefunctionsignature.Howtodo?CaseStudy1-2Function

OverloadingvoidprintGradeBook(int

sNo[],int

g[]){cout<<"----------------------------\n";cout<<"StudentNoGrade\n";for(inti=0;i<studentNum;i++) cout<<sNo[i]<<g[i]<<endl;cout<<"----------------------------\n";cout<<"Theaveragegrade:"<<average(g)<<endl;}voidprintGradeBook(int*sNo,string*sName,int*sg){cout<<"----------------------------\n";cout<<"StudentNoNameGrade\n";for(inti=0;i<studentNum;i++) cout<<sNo[i]<<sName[i]<<sg[i]<<endl;cout<<"----------------------------\n";cout<<"Theaveragegrade:"<<average(sg)<<endl;}printGradeBook(studentNo,grade);printGradeBook(studentNo,studentName,grade);voidprintGradeBook(int*sNo,string*sName,int*sg);voidprintGradeBook(intsNo[],intg[]);Whenyoudefineoverloadedfunctions,youmustprovideaparameterlistwithdifferentparameters.Function

Overloading-HowtoCallanOverloadedFunctionMakingacalltoanoverloadingfunctionresultsinoneofthethreepossibleoutcomes:AmatchisfoundNomatchisfoundAnambiguousmatchisfoundFunction

Overloading–HowtoCallanOverloadedFunctionTrytofindanexactmatchTrytofindamatchthroughpromotions

booltoint

chartoint

e.g.charc=‘a’;

shorttoint

floattodoubleTrytofindamatchthroughstandardconversions

inttodouble

doubletointe.g.doublea=3.4;intn=(int)a;

doubletolongdoubleT*tovoid*

derived*toBase*

inttounsigned