或物件所属的空间名称

ObjectorientedprogrammingWhatisClass?WhatisObject?Fromobject-orientedpointofviewClassisauser-defineddatatypewhichcontainsrelevantdataandfunctionsObjectisavariabledeclaredundersomeclassdatatypeFromphilosophyconceptClassisanabstractconceptthatdescribestheattributesofacollectionofobjects1FromCtoC++Namespace變數、函數、或物件所屬旳空間名稱,在不同旳namespace中可使用相同旳變數名稱。std:C++全部系統提供旳函數所屬旳namespaceavoidconflictofvariablenamesinthedifferentclasslibraries2namespaceexample//Thisprogramoutputsthemessage////C++:onesmallstepfortheprogram,//onegiantleapfortheprogrammer////tothescreen#include<iostream>usingnamespacestd;intmain(){cout<<"C++:onesmallstepfortheprogram,\n"<<"onegiantleapfortheprogrammer\n";return0;}comparetoC:#include<stdio.h>main(){

printf(“….”);withoutnamespace3namespacescreatenamespaceexamples: namespacemfc{ intinflag; voidg(int);…}namespaceowl{ intinflag; …}4namespaceusevariablesinanamespaceusescoperesolutionoperator::e.g.mfc::inflag=3;owl::inflg=-823;cout<<mfc::inflag;theusingdirectivee.g..usingnamespacemfc;inflag=3;//相當於mfc::inflag=3;owl::inflag=-823;5C++Input/OutputC++Input/Outputobjectscin standardinputcout standardoutputcerr standarderrore.g.cin>>x;cin>>len;cout<<x;cout<<len;cin>>x>>len;

cout<<x<<len;6C++Input/Outputexample#include<iostream>usingnamespacestd;intmain(){intid;floatav;cout<<“Entertheidandtheaverage:”;cin>>id>>av;cout<<“Id:”<<id<<‘\n’<<“Average:”<<av<<‘\n’;return0;}Entertheidandtheaverage:90003890.8Id:900038Average:90.8

7C++InputOutputManipulatorsfortheformatofI/Osetwidthton:setw(n)for(i=1;i<=1000;i*=10)cout<<setw(6)<<i<<‘\n’;11010010008manipulatorsendl:endofline,writenewlinee.g.inti=4,j=6,k=8;charc=‘!’;cout<<i<<c<<endl<<j<<c<<‘\n’ <<k<<c<<endl;4!6!8!9manipulatorsoct(octal),hex(hexadecimal),dec(decimal)e.g.inti=91;cout<<“i=“<<i<<“(decimal)\n”;cout<<“i=“<<oct<<i<<“(octal)\n”;cout<<“i=“<<hex<<i<<“(hexadecimal)\n”;cout<<“i=“<<dec<<i<<“(decimal)\n”;i=91(decimal)i=133(octal)i=5b(hexadecimal)i=91(decimal)10manipulatorslistedinchap.14-9dec,endl,fixed,flush,hex,left,oct,right,scientific,setfill(c),setprecision(n),setw(n),showpoint,noshowpoint,showpos,noshowpos,skipws,noskipws,ws

11manipulatorssetfill,setprecisione.g.floata=1.05,b=10.15,c=200.87;cout<<setfill(‘’)<<setprecision(2);cout<<setw(10)<<a<<‘\n’;cout<<setw(10)<<b<<‘\n’;cout<<setw(10)<<c<<‘\n’;******1.05*****10.15****200.8712files(example)#include<fstream>usingnamespacestd;constintcutoff=6000;constfloatrate1=0.3;constfloatrate2=0.6;intmain(){ifstreaminfile;ofstreamoutfile;intincome,tax;infile.open("income.txt");outfile.open("tax.txt");while(infile>>income){if(income<cutoff)tax=rate1*income;elsetax=rate2*income;outfile<<"Income="<<income<<"greenbacks\n"<<"Tax="<<tax<<"greenbacks\n";}infile.close();outfile.close();return0;}13files(examplecont.)inputfile“income.txt”22141050031010result:outputfile“tax.txt”Income=2214greenbacksTax=664greenbacksIncome=10500greenbacksTax=6299greenbacksIncome=31010greenbacksIncome=18605greenbacks14filestestingwhetherfilesareopenfileobjectconvertsto‘true’ifopensuccessfully,otherwiseconvertsto‘falsee.g.ifstreaminfile;ifstream.open(“scores.dat”);…if(infile){…}//ifopensucessfullyorif(!infile){…}//iffailtoopenthefile15filese.g..ifstreaminfile;infile.open(“scores.dat”);if(!infile){cerr<<“Unabletoopenscores.dat\n”;exit(0);}16C++featuresbooldatatypevalues:true(1)orfalse(0)manipulators:boolalpha,noboolalpha(default)e.g.boolflag;flag=(3<5);cout<<flag<<‘\n’;cout<<boolalpha<<flag<<‘\n’;1true17thetypestringstringinitializatione.g.#include<string>strings1;strings2=“Bravo”;strings3=s2;strings4(10,’x’);cout<<s1<<‘\n’;cout<<s2<<‘\n’;cout<<s4<<‘\n’;Bravoxxxxxxxxxx

18thetypestringC-stylestring(endwithanullchar‘\0’)charmystring=“astring”;orcharmystring[]=“astring”;printf(“%s\n”,mystring);charmystring[9]thenullcharacter‘\0’isaddedbytheCcompilerautomaticallyastring\0

19thetypestringstringlengthstrings=“EdWood”;cout<<“Length=“<<s.length()<<‘\n’;inputastringseparatebyspaceornewlinecout<<“Enterastring:”;cin>>s;cout<<s;Length=7

EdWoodEd20getlinefunctionexample(copyfile)#include<iostream>#include<fstream>#include<string>usingnamespacestd;intmain(){stringbuff;ifstreaminfile;ofstreamoutfile;cout<<“Inputfilename:”;cin>>buff;infile.open(buff.c_str());cout<<“Outputfilename:”;cin>>buff;outfile.open(buff.c_str());while(getline(inflie,buff))outfile<<buff<<“\n\n”;infile.close();outfile.close();return0;}21thetypestringinputalineofstringfromcinstirngs;getline(cin,s);concatenationofstringstrings1=“Atlas”,s2=“King”,s3;s3=s1+s2;cout<<s1<<‘\n’;cout<<s2<<‘\n’;cout<<s3<<‘\n’;AtlasKingAtlasKing22thetypestringremoveasubstrings.erase(position,length);e.g.strings=“RayDennisSteckler”;s.erase(4,7);cout<<s<<‘\n’;RaySteckler23thetypestringinsertastrings.insert(position,str2);replaceasubstrings.replace(startpos,length,str2);swapstringss1.swap(s2);extractasubstrings.substr(position,length)24thetypestring[]operatorstrings=“Nan”cout<<s[1];<<‘\n’;s[0]=‘J’;cout<<s<<‘\n’;searchasubstrings1.find(s2,position);comparestrings==,!=,<,>,<=,>=aJan25functionsreferencevariablesprovidesanalternativenameforstoragee.g.memoryintx;int&ref=x;xrefx=3;cout<<ref;326functionscallbyvalue(defaultinC)passvaluestothecalledfunctioncallbyreferencepassaddressestothecalledfunctionprovidedinC++,butnotinCe.g.voidswap(int&,int&);27callbyreference#include<iostream>usingnamespacestd;voidswap(int&,int&);intmain(){inti=7,j=-3;swap(i,j);cout<<“i=“<<i<<‘\n’<<“j=“<<j<<‘\n’;return0;}voidswap(int&a,int&b){intt;t=a;a=b;b=t;}

passaddressofi,jtoa,b

main()

swap()tiajb7-3

i=-3j=728callbyreferenceinC(usepointer)#include<stdio.h>voidswap(int*,int*);//functionprototypemain(){inti=7,j=-3;swap(&i,&j);//passingaddressesofiandjprintf(“i=%dj=%d”,i,j);}voidswap(int*a,int*b){//usepointersparametersinsteadintt;//ofreferencevariablest=*a;*a=*b;*b=t;//usepointerstoreferencethe}//valuesinmainfunction29functionsoverloadingfunctionsfunctionscanhavethesamename,butfunctionsignaturesneedtobedistinctfunctionname,andnumber,datatype,andorderofitargumentse.g.voidprint(inta);voidprint(doublea);//o.k.voidprint(inta,intb);//o.k.intprint(inta);//wrong!,returntypeisnotpartofsignatures30functionsdefaultargumentsalltheparameterswithoutdefaultvaluesmustcomefirstintheparameterlist.bettertospecifyintheprototype,e.g.voidf(intval,floats=12.6,chart=‘\n’,stringmsg=“Error”);validinvocationf(14,48.3,‘\t’,“ok”);//s=48.3,t=‘\t’,msg=“ok”f(14,48.3);//s=48.3,t=‘\n’,msg=“Error”f(14);//s=12.6,t=‘\n’,msg=“Error”31functionsoverloadingfunctionsfunctionscanhavethesamename,butfunctionsignaturesneedtobedistinctfunctionnamenumber,datatype,andorderofitargumentse.g.voidprint(inta);voidprint(doublea);//o.k.voidprint(inta,intb);//o.k.intprint(inta);//wrong!returntypeisnotpartofsignatures32overloadingfunctions#include<iostream>#include<iomanip>voidprint(inta);voidprint(doublea);intmain(){intx=8;doubley=8.0;print(x);print(y);return0;}voidprint(inta){cout<<a<<‘\n’;}voidprint(doublea){cout<<showpoint<<a<<‘\n’;}88.00033dynamic(vs.static)allocationdynamicallocationpointer_var=newdata-type;//singledatapointer_var=newdata-type[size];//arraye.g.int*int_ptr;

int_ptr=newint;ptrint*ptr;ptr=newint[100];ptr[0]ptr[1]…ptr[99]…34dynamicallocationdelete,delete[]freestorageallocatedbynewornewtype[size]e.g.deleteint_ptr;delete[]ptr;linkedlistexamplenamenextstart‧‧‧

“林旺”“馬蘭”“阿美”035dynamicallocation#include<string>usingnamespacestd;structElephant{stringname;Elephant*next;};voidprint_elephants(constElephant*ptr);Elephant*get_elephants();voidfree_list(constElephant*ptr);intmain(){Elephant*start;start=get_elephants();print_elephants(start);free_list(start);return0;}36dynamicallocationElephant*get_elephants(){Elephant*current,*first;intresponse;current=first=newElephant;cout<<"\nNAME:";cin>>current->name;cout<<"\nAddanother?(1==yes,0==no):";cin>>response;//AddElephantstolistuntilusersignalshalt.while(response==1){