C++大學(xué)教程課后習(xí)題答案11

Chapter12

SeparateCompilationandNamespaces

1.SolutionstoandRemarksonSelectedProgrammingProblems

1.DigitalTime

AddthefollowingmemberfunctiontotheADTclassDigitalTime.definedinDisplay

12.1and12.2.

void

DigitalTime：：interval_since(constDigitalTime&aPreviousTime,

int&hourslnlnterval,

int&minutesInInterval)；

Thedifferenceintheelapsedtimebetweenthetimeofthecallingobjectandthetimeof

theargumentobjectisreportedintheargumentsfortheintreferenceshoursandminutes

parameters.

Questionarisinginthesolution:Inexactlywhatdays(previous,current,successor)are

thesetimesallowedtobe?

Bothtimesinthesame(current)day,orcurrenttimeisinthecurrentdayandtheprevious

timeisinthepreviousday.

ThisBooleanexpressionistrueiftheprevioustimeisinthepreviousday:

(hour<prev.hour||hour==prev.hour&&minute<

prev.minute)

Thetimedifference

(callingobjtime)-(argumentpreviousobjtime)

actuallymeans

(callinghours：minutes)-(argumentprevioushours：minutes)

Copyright?2008PearsonEducation,Inc.PublishingasPearsonAddison-Wesley

This(perhaps)maybemoreclearlywritten

(caller_hours-prev_hours)：(caller_minutes-prev_minutes)

raw_difference=

(caller_hours-prev_hours)：(caller_minutes-prev_minutes)

whichwillneedfixingifeitherthehourortheminutearenegative.

Someexamples:

Timesinsameday,bothdifferencespositive:

11:1515:30

a_previous_timecallertime

raw_difference=(15-11)：(30-15)=4：15

0<difference_minutes<60,

Sowedon'tneedtofixthetime.

difference=raw_difference

Timesinsameday,minutesdifferencesnegative:

I.I

11:305:15

a_previous_timecallertime

raw_difference=(15-11)：(15-30)=4：(-15)

Thedifference_minute<0,sowedecrementhoursandadd60minutesto

minute,gettingtheintervalsincea_previous_time=3:45

Exampleswhereprevioustimeislaterthancaller'stime,sotimesareindifferent

days.

Wehavetimesondifferentdaysifthe

rawdifferencehour<0or

rawdifferencehour=0andrawdifferenceminute<0

thatis

(hour<prev.hour||hour==

prev.hour&&minute<prev.minute)

Whencaller'stimeisonapreviousday,add24toraw_differenceandfixminutesif

necessary.

Differencehoursnegative,differenceminutespositive:

previousdaycurrentday

||

12:3011:15

a_previous_timecallertime

raw_difference=(11-12)：(15-30)=(-1)：(-15)

difference=raw_difference+24:00

=(-1):(-15)+24:00=23:(-15)

differenceminutes<0,

whichwefixbyadding60anddecrementinghourstoget22:45

Bothdifferencehoursanddifferenceminutesarenegative:

previousdaycurrentday

||

12:1511:30

a_previous_timecallertime

raw_difference=(11-12)：(30-15)=(-1)：15

difference=raw_difference+24:00

=(-1):15+24:00=23:15

(differenceminutes>0sonofixisneeded)

previousdaycurrentday

12：5911：01

previoustimecaller'stime

raw_difference

=(caller_hours-prev_hours)：(caller_min-prev_min)

=(11-12):(01-59)=(-1):(-58)

difference=raw_difference+24：00

=(-1):(-58)+24:00=23:(-58)

minutes<0,

soweneedtofixbydecrementinghoursandadding60tominutes.Thefixedtimeis

22:02

TheclassDigitalTimedefinition,withintervalsinceadded:

//file：dtime.h

//modifiedfromtextforChapter12problem1byaddition

//ofpublicfunctionsnormalizeandinterval_since.

//InterfaceforclassDigitalTime

//valuesareinputandoutputin24hourtime：

//9:30AMis9:30,and2:45PMis14:45

#include<iostream>

usingnamespacestd；

classDigitalTime

public：

friendbooloperator==(constDigitalTime&zconst

DigitalTime&)；

DigitalTime(intthe_hourzintthe_minute)；

DigitalTime()；//settimetomidnight：0:00

voidadvance(intminutes_added)；

voidadvance(inthours_addedzintminutes_added)；

friendistream&operator>>(istream&,DigitalTime^)；

friendostream&operator<<(ostream&zconstDigitalTime^)；

//memberaddedforProgrammingProblem1zpage488

voidinterval_since(constDigitalTime&prev_timez

int&hours_in_interval,

int&minutes_in_interval)const；

private：

inthour；

intminute；

);

Thetestprogram:

//File：chl2prbl.cc

//Chapter12problem1：interval_sincetestprogram.

#include<iostream>

#include"dtime.hn

usingnamespacestd；

intmain()

cout<<"TestProgrammingProblem1n<<endl<<endl；

DigitalTimecurrentzprevious；

inthourszminutes；

charans；

do

cout<<"Enteracurrenttimein24hournotation"；

cin>>current；

cout<<""<<current<<endl

<<nEnteraprevioustimein24hournotation；

cin>>previous；

cout<<*'*'<<previous<<endl；

erval_since(previouszhourszminutes)；

cout<<"Thetimeintervalbetween”<<previous

<<'*and"<<current<<endl

<<"is"<<hours<<"hoursand"

<<minutes<<Hminutes11<<endl；

cout<<nY/yrepeats,anyothercharacterends"<<endl；

cin>>ans；

cout<<nn<<ans<<endl；

}while(1y*==ans||1Y1==ans)；

return0；

)

Hereisthecodeforthefunctionintervalsince:

#include"dtime.hn

ttinclude<iostream>

usingnamespacestd；

void

DigitalTime：：interval_since(constDigitalTime&prevz

int&hours_in_intervalz

int&minutes_in_interval)const

{——

DigitalTimedifference；

difference.hour=hour-prev.hour；

difference.minute=minute-prev.minute；

if(hour<prev.hour

hour==prev.hour&&minute<prev.minute)

(

cout<<n1Previous*timeisinthepreviousday"

<<endl；

difference.hour=24+(hour-prev.hour)；

)

if(difference.minute<0)

(

difference.hour--；

difference.minute=difference.minute+60；

)

hours_in_interval=difference.hour；

minutes_in_interval=difference.minute；

)——

Testdataforatypicalrun:

3:155:30y3:305:15y5:153:30y5:303:15y11:5911:58y

11:5811:59y

12:0112:00y12:0012:01n

Outputfromatypicalrun,generatedbythiscommandissuedatthecommand

prompt:

13:32:29:-/AW$chl2prbl<chl2prbl.in>chl2prbl.out

13:32：31:^/AW$catchllprbl.out

TestProgrammingProblem1

Enteracurrenttimein24hournotation3：15

Enteraprevioustimein24hournotation5:30

1Previous*timeisinthepreviousday

Thetimeintervalbetween5:30and3：15

is21hoursand45minutes

Y/yrepeats,anyothercharacterends

y

Enteracurrenttimein24hournotation3:30

Enteraprevioustimein24hournotation5：15

'Previous*timeisinthepreviousday

Thetimeintervalbetween5：15and3:30

is22hoursand15minutes

Y/yrepeats,anyothercharacterends

y

Enteracurrenttimein24hournotation5：15

Enteraprevioustimein24hournotation3:30

Thetimeintervalbetween3:30and5：15

is1hoursand45minutes

Y/yrepeats,anyothercharacterends

y

Enteracurrenttimein24hournotation5:30

Enteraprevioustimein24hournotation3：15

Thetimeintervalbetween3：15and5:30

is2hoursand15minutes

Y/yrepeats,anyothercharacterends

y

Enteracurrenttimein24hournotation11:59

Enteraprevioustimein24hournotation11:58

Thetimeintervalbetween11:58and11:59

is0hoursand1minutes

Y/yrepeatszanyothercharacterends

y

Enteracurrenttimein24hournotation11:58

Enteraprevioustimein24hournotation11:59

1Previous*timeisinthepreviousday

Thetimeintervalbetween11:59and11:58

is23hoursand59minutes

Y/yrepeats,anyothercharacterends

y

Enteracurrenttimein24hournotation12:01

Enteraprevioustimein24hournotation12:00

Thetimeintervalbetween12:00and12:01

is0hoursand1minutes

Y/yrepeatszanyothercharacterends

y

Enteracurrenttimein24hournotation12:00

Enteraprevioustimein24hournotation12:01

'Previous1timeisinthepreviousday

Thetimeintervalbetween12:01and12:00

is23hoursand59minutes

Y/yrepeatszanyothercharacterends

n

Optional:TheMakeUtilityandMakefiles:

InordertocompilethefilesfromthisproblemIcouldhavetypedin

g++dtime.ccchl2prbl.add.ccchl2prbl.cc

eachtimeIwantedtocompileandlinkthefiles.Instead,Icreatedafile,called

makefile,orMakefile,whichisinterpretedbythemakeprogram.(Fmtalkingabout

Unix/Linuxmake,butBorlandandotherC++compilervendorshaveprogramswith

similarcapability,butsomewhatdifferentsyntaxforthemakefile.)

Themakeutilityenablesyoutosplitthecompilingofalargeprogramintotheautomatic

compilinganumberofsmallerpieces,thenautomaticallycallingthelinkprogramtohook

yourpiecestogether.

HereisthemakefileIusedtocompilethisprogram,completewiththedidactic

commentaryIhabituallyputintomyprogramsandutilities.

#File：makefile

#For：Chapter12Problem1.

#Use：tocreateyourexecutablezissuethecommand：

#

#make

#

#toremovethe.ofiles,issuethecommand：

#

#makeclean

chl2prbl：chl2prbl.ochl2prbl.add.odtime.odtime.h

g++-ochl2prblchl2prbl.ochl2prbl.add.odtime.o

#leadcharactermustbea<tab>.Withoutitzyougeta

#(notveryclear)errormessagefrommakesuchas

#Makefile：12：missingseparator.Stop.

#The12isthelinenumberwheretheerrorwasdetected.

#Thenextlinesareacleanupforuseaftercompiling.

clean：

rmchl2prbl.odtime.ochl2prbl.add.o

#leadcharactermustbea<tab>.Withoutityougetanerror

frommake

#Makefile：20：missingseparator.Stop.

#The20isthelinenumberwheretheerrorwasdetected.

IwilldiscusstheMakefilelinebyline.

NamethiseitherMakefileormakefile,andkeepitinthesamedirectorywithyour

C++codefiles.ThemakeprogramselectsmakefilebeforeMakefiletofollowinthe

compilingofaprogram.

Thelinesthatbeginwith#arecomments.Thelinesthatstartwithanidentifierfollowed

bya：,followedbyasequenceoffilenameswitha.oextension,arecalleddependency

lines.Theidentifierisjustalabel.Itcouldbecow：aswellaschllprbl：.Itsays

wehaveatask,andthattaskdependsonthesefileswith.oextensions,andanything

thesefilesdependon(inparticular,thefilenameuptothe.ofollowedby.cc.

becausethefilename.ccmustbecompiledtogetthefilename.o.)Ifanyofthese

filesarechanged,thecommandfollowingthislinewillbeexecutedtocreatethe.ofiles.

Inshort,thepresenceofeachofthe.ofilesinthislinetellsthemakeprogramthatitis

tolookfor.ccfileswiththesamenameuptothe.o,andcompilethesewiththe

compilernameonthenextline.

Thelinefollowingthetargetanddependencylistisacommandthattellsmakehowto

'make'theprogramwhosenameisgivenfollowingthe-ooption.Inthiscase,Bythe

way,theleadingcharacteronthisnextlineisa<tab>.Themakeprogramrequiresthat

thisbeatabcharacter.

Themakeprogram,unlessdirectednottodosowiththe-scommandlineoption,displays

eachcommanditexecutes.

15:46:37：-/AW$make

make：'chl2prbl1isuptodate.

Here,Ihadjustrunmake,andIranitagain.Themakeinterpreterlookedatthedates

andtimesonthefilesinthemakefileandfoundthatthecompiledversionswerealllater

thanthe.ccand.hfiles,soitconcludedthatthatacompilehadbeendonesincethesource

fileshadbeenedited.

15:46:39：-/AW$makeclean

rmchl2prbl.odtime.ochl2prbl.add.o

Makedidthecommandlinejustbelowtheclean:target.Thiskindoftargetiscalledafake

target,sinceitdoesnotcreateanyprograms.Itonlyexiststoenablethetaskonthenext

linetobedoneforus.

15:46:42：-/AW$make

g++-cchl2prbl.cc-ochl2prbl.o

g++-cchl2prbl.add.cc-ochl2prbl.add.o

g++-cdtime.cc-odtime.o

g++-ochl2prblchl2prbl.ochl2prbl.add.odtime.o

15:46:54:-/AW$15:46:37:-/AW$

Thistimemakelookedforandcompiledeachprogramfile,inturn,thenlinkedtheobject

filestogetherinthelastline.

Makecancompilepartofacollectionofsourcefiles,orallofthem.Oncethecompileis

done,installtheresultsofthecompilationinwhateverdirectoriesyouspecify.

Finally,g++andgcchavethefacilitytocreatecommandanddependencylinesthatcanbe

usedinamakefile.Themanualpageforgcc/g++willshedsomelighthere.

Reference:Makehasalanguageallitsownformakefiles.Agoodbeginningbookonthe

makefacilityistheO'ReillybookManagingProgramswilhMakementionedabove.

2.DoSelf-TestExercise5infulldetail.WritethecompleteADTclassincluding

interfaceandimplementationfiles.AlsowriteaprogramtotestyourADTclass.

Nosolutionisprovidedforthisexercise.

3-5.NoSolutionsProvided.

6.RationalNumberClass-separatecompilation

ExtendsChapter11Problem5touseseparatelycompiledfiles.

Thisisthetestprogram,theHeader,rational.h,containstheclassdefinitionsandthe

implementationareinchl2.6.cpp

Thisproblemrequiresimplementationofaclassforrationalnumberofthetype2/3.

Requirements:

classRational；

privatedata：intn,(fractionnumerator)andintd(fraction

denominator).

publicinterface：

constructors：

twointargs,toallowsettingrationaltoanylegalvalue

oneintarg,toconstructrationalswithargnumeratoranddenominator1.

overload<<and>>toallowwritingtoscreeninform325/430

andreadingitfromthekeyboardinthesameformat.

Notes:eithernordmaycontainanegativequantity.

Overload+-*/<<=>>===

Putdefinitionsinseparatefileforseparatecompilation

Testprogramrequired.

"Warning:*

VC++6,asdistributedWILLNOTCOMPILECODETHATUSESfriendsundersome

circumstances.YOUMUSTHAVEATLEASTPATCHLEVEL5INSTALLED.I

compiledthisusingthelatestVisualStudiopatchesatlevel.6.

//Filechl2.6.tst.cpp

//

//TestprogramforRationalclass

#include<iostream>

usingnamespacestd；

#include"rational.h"

int

mam()

cout<<"Testingdeclarations1'<<endl；

cout<<nRationalx,y(2),z(-5,-6),w(1,-3)；'?<<endl；

Rationalx,y(2)zz(-5,-6),w(1z-3)；

cout<<'?z=?'<<z<<"，y="<<y<<",z="<<z

<<",w="<<w<<endl；

cout<<"Testing>>overloading：\nEnter"

<<"afractionintheformat"

<<"integer_numerator/integer_denominator"

<<endl；

cin>>x；

cout<<"Youenteredtheequivalentof："<<x<<endl；

cout<<z<<"-("<<w<<")="<<z-w<<endl；

cout<<"Testingtheconstructorandnormalizationroutines："<<endl；

y=Rational(-128z-48)；

cout<<"y=Rational(-128,-48)outputsas"<<y<<endl；

y=Rational(-128,48)；

cout<<"y=Rational(-128z48)outputsas?'<<y<<endl；

y=Rational(128,-48);

cout<<"y=Rational(128z-48)outputsas"<<y<<endl；

Rationala(1z1)；

cout<<'?Rationala(1,1)；aoutputsas："<<a<<endl；

Rationalww=y*a；

cout<<y<<"*"<<a<<?'="<<ww<<endl；

w=Rational(25,9);

z=Rational(3,5);

cout<<"Testingarithmeticandrelational

<<"operatoroverloading"<<endl；

cout<<w<<ii*II<<z<<II_II<<w*z<<endl

cout<<w<<ii+II<<z<<fl_fl<<w+z<<endl

cout<<w<<II-II<<z<<fl_II<<w-z<<endl

cout<<wVVII/!l<<z<<11_II<<w/z<<endl

cout<<w<<<<<z<<*'=H<<(w<z)<<endl；

cout<<w<<<"<<w<<"="<<(w<w)<<endl；

cout<<w<<<="<<z<<<<(w<=z)<<endl；

cout<<w<<<="<<w<<<<(w<=w)<<endl；

cout<<w<<<<(w>z)<<endl；

cout<<w<<<<(w>w)<<endl；

cout<<w<<<<(w>=z)<<endl；

cout<<w<<<<(w>=w)<<endl；

w=Rational(-21z9);

z=Rational(3z5);

cout<<w<<<<w*z<<endl；

cout<<w<<<<w+z<<endl；

cout<<w<<<<w-z<<endl；

cout<<w<<<<w/z<<endl；

cout<<w<<<<(w<z)<<endl；

cout<<w<<<<(w<w)<<endl；

cout<<w<<<<(w<=z)<<endl；

cout<<w<<<<(w<=w)<<endl；

cout<<w<<<<(w>z)<<endl；

cout<<w<<<<(w>w)<<endl；

cout<<w<<<<(w>=z)<<endl；

cout<<w<<<<(w>=w)<<endl；

return0；

)

//endfilechl2.5.tst.cpp

/*

TypicalRun：

Testingdeclarations

Rationalx,y⑵，z(-5,-6),w(1z-3)；

z=5/6zy=2/1zz=5/6zw=-1/3

Testing<<overloading：

Enterafractionintheformatinteger_numerator/integer_denominator

Youenteredtheequivalentof：9/7

5/6-(-1/3)=7/6

Testingtheconstructorandnormalizationroutines：

y=Rational(-128z-48)outputsas8/3

y=Rational(-128z48)outputsas-8/3

y=Rational(128,-48)outputsas-8/3

Rationala(1,1)；aoutputsas：1/1

-8/3*1/1=-8/3

Testingarithmeticandrelationaloperatoroverloading

25/9*3/5=5/3

25/9+3/5=152/45

25/9-3/5=98/45

25/9/3/5=125/27

25/9v3/5=0

25/9<25/9=0

25/9<=3/5=0

25/9<=25/9=1

25/9>3/5=1

25/9>25/9=0

25/9>=3/5=1

25/9>=25/9=1

-7/3*3/5=-7/5

-7/3+3/5=-26/15

-7/3-3/5=-44/15

-7/3/3/5=-35/9

-7/3<3/5=1

-7/3<-7/3=0

-7/3<=3/5=1

-7/3<=-7/3=1

-7/3>3/5=0

-7/3>-7/3=0

-7/3>=3/5=0

-7/3>=-7/3=1

***************************************************************

IMPLEMENTATION

***************************************************************

/*

6

.RationalNumberClass--separatecompilation

ExtendsChapter11Problem5touseseparatelycompiledfiles.

THESEARETHEIMPLEMENTATIONS.TheHeader,rational.h,containsthe

classdefinitionsandthetestprogramisinchl2.6.tst.cpp

Thisproblemrequiresimplementationofaclassfor

rationalnumberofthetype2/3.

*/

//file：chl2.6.cpp

//ImplementationsofthemembersofclassRational.

//ForChapter12Problem6

#include<iostream>

#include<cstdlib>

usingnamespacestd；

#include"rational.h"

//privatemembersofclassRational

//intn；

//intd；

Rational：：Rational(intnumer,intdenom)

(

normalize(numer,denom)；

n=numer；

d=denom；

)

//setsdenominatorto1

Rational：：Rational(intnumer)：n(numer),d(1)

//Seetheinitializerappendix

(

//bodydeliberatelyempty

)

//setsnumeratorto0,denominatorto1

Rational：：Rational()：n(0)zd(1)

//seeinitializerappendix

(

//bodydeliberatelyempty

)

Rationaloperator+(constRational&left,

constRationaleright)

(

intnumer=left.n*right.d+left.d*right.n；

intdenom=left.d*right.d；

normalize(numer,denom)；

Rationallocal(numer,denom)；

returnlocal；

)

Rationaloperator-(constRationaleleft,

constRationaleright)

(

intnumer=left.n*right.d-left.d*right.n；

intdenom=left.d*right.d；

normalize(numer,denom)；

Rationallocal(numer,denom)；

returnlocal；

)

Rationaloperator*(constRationaleleft,

constRationaleright)

(

Rationalproduct；

intnumer=left.n*right.n；

intdenom=left.d*right.d；

normalize(numer,denom)；

product=Rational(numer,denom)；

returnproduct；

)

Rationaloperator/(constRationaleleft,

constRationaleright)

(

Rationalquotient；

intnumer=left.n*right.d；

intdenom=left.d*right.n；

normalize(numer,denom)；

quotient=Rational(numer,denom)；

returnquotient；

)

//precondition：allrelationaloperatorsrequired>0

booloperator<(constRationaleleft,

constRationaleright)

returnleft.n*right.d<right.n*left.d；

}

booloperator<=(constRationaleleftz

constRational&right)

(

returnleft.n*right.d<=right.n*left.d；

)

booloperator>(constRationaleleft,

constRationaleright)

(

returnleft.n*right.d>right.n*left.d；

)

booloperator>=(constRational&leftz

constRationaleright)

(

returnleft.n*right.d>=right.n*left.d；

)

booloperator==(constRationalaleft,

constRational&right)

(

returnleft.n*right.d==right.n*left.d；

)

//NOTE:

//Doinginputchangestheinputstreamstate.Thisseems

//obvious,butIhavestudentswhodidn1trealizethis.

//Thiscode,alongwithiostreamlibrary,goesintoan

//infiniteloopifyoumakeistreamaconstreference.There

//arenoerrormessages,onlyaninfiniteloop,involving

//thesingleparameterconstructor.Thiscanbequite

//disconcertingtothenaivestudent.

//

//Bottomline：ThefirstparamMUSTNOTbeconst.The

//secondoneiswritten,soitcannotbeconsteither.

istream&operator>>(istream&in_str,Rationaleright)

(

charch；

in_str>>right.n>>ch>>right.d；

if(ch!='/1)//properlydone,wewouldsetiostream

//state

{//tofailhereincaseoferror.

cout<<"badinputformatforoperator>>.Aborting!?'

<<endl；

exit(1)；

)

normalize(right.n,right.d)；

returninstr；

}

//This,liketheabovecase,alongwithg++iostream

//library,goesintoaninfiniteloopwhenyouattemptto

//makeostreamaconstreference.

//Therearenoerrormessages,onlyaninfiniteloop,

//involvingthesingleparameterconstructor.

//

//Bottomline：Thefirstparametershouldnotbeconst,the

//secondisreadonlyandshouldbeconst.

ostream&operator<<(ostream&out_strz

constRational&right)

(

out_str<<right.n<<'/'<<right.d；

returnout_str；

}一

//postcondition：returnvalueisgcdoftheabsolutevalues

//ofmandndependsonfunctionintabs(int)；declaredin

//cstdlib

intgcd(intm,intn)

(

intt；

m=abs(m)；//don'tcareaboutsigns.

n=abs(n)；

if(n<m)//makem>=nsoalgorithmwillwork1

(

t=m；

m=n；

n=t；

)

intr；

r=m%n；

while(r!=0)

(

r=m%n；

m=n；

n=r；

)

returnm；

)

//postcondition：nandd(tobenumeratoranddenominator

//ofafraction)haveallcommonfactorsremoved,andd>0.

voidnormalize(int&n,int&d)

(

//removecommonfactors：

intg=gcd(n,d)；

n=n/g；

d=d/g；

//fixthingssothatifthefractionis'negative,

//itisnthatcarriesthesign.Ifbothnanddare

//negativezeachismadepositive.

if(n>0&&d<0||n<0&&d<0)

(

n