Exercise2.82Showhowtogeneralizeapply-generictohandlecoercioninthegeneralcaseofmultiplearguments.Onestrategyistoattempttocoercealltheargumentstothetypeofthefirstargument,thentothetypeofthesecondargument,andsoon.

Exercise2.80Defineagenericpredicate=zero?thattestsifitsargumentiszero,andinstallitinthegenericarithmeticpackage.Thisoperationshouldworkforordinarynumbers,rationalnumbers,andcomplexnumbers.这道题更简单，直接与0相比较就行，以下

Exercise2.79Defineagenericequalitypredicateequ?thatteststheequalityoftwonumbers,andinstallitinthegenericarithmeticpackage.Thisoperationshouldworkforordinarynumbers,rationalnumbers,andcomplexnumbers.这道题也挺简单的，分别在

Exercise2.78Theinternalproceduresinthescheme-numberpackageareessentiallynothingmorethancallstotheprimitiveprocedures+,-,etc.Itwasnotpossibletousetheprimitivesofthelanguagedirectlybecauseourtype-tagsystemrequiresthat

Exercise2.77LouisReasonertriestoevaluatetheexpression(magnitudez)wherezistheobjectshowninFigure2.24.Tohissurprise,insteadoftheanswershegetsanerrormessagefromapply-generic,sayingthereisnomethodfortheoperationmagni

Exercise2.74InsatiableEnterprises,Inc.,isahighlydecentralizedconglomeratecompanyconsistingofalargenumberofindependentdivisionslocatedallovertheworld.Thecompany’scomputerfacilitieshavejustbeeninterconnectedbymeansofacle

最近状态不太好，再加上2.73前面的内容有点多，学的有点吃力，所以昨天就没做。。Exercise2.73Section2.3.2describedaprogramthatperformssymbolicdifferentiation:(define(derivexpvar)(cond((number?exp)0)((variable?exp)(if(same-va

Exercise2.72ConsidertheencodingprocedurethatyoudesignedinExercise2.68.Whatistheorderofgrowthinthenumberofstepsneededtoencodeasymbol?Besuretoincludethenumberofstepsneededtosearchthesymbollistateachnodeencounter

Exercise2.71SupposewehaveaHuffmantreeforanalphabetofnsymbols,andthattherelativefrequenciesofthesymbolsare1,2,4,...,2n1.Sketchthetreeforn=5;forn=10.Insuchatree(forgeneraln)howmanybitsarerequiredtoencode

Exercise2.70Thefollowingeight-symbolalphabetwithassociatedrelativefrequencieswasdesignedtoefficientlyencodethelyricsof1950srocksongs.(Notethatthe“symbols”ofan“alphabet”neednotbeindividualletters.)A2GET2SHA3

Exercise2.69Thefollowingproceduretakesasitsargumentalistofsymbol-frequencypairs(wherenosymbolappearsinmorethanonepair)andgeneratesaHuffmanencodingtreeaccordingtotheHuffmanalgorithm.(define(generate-huffman-treepairs)

Exercise2.66Implementthelookupprocedureforthecasewherethesetofrecordsisstructuredasabinarytree,orderedbythenumericalvaluesofthekeys.这道题还是挺简单的，由于是有序的二叉树，所以可以先比较根与要查找的数字的大小，如果相等就查到了；如果根

Exercise2.63Eachofthefollowingtwoproceduresconvertsabinarytreetoalist.(define(tree->list-1tree)(if(null?tree)'()(append(tree->list-1(left-branchtree))(cons(entrytree)

Exercise2.60Wespecifiedthatasetwouldberepresentedasalistwithnoduplicates.Nowsupposeweallowduplicates.Forinstance,theset{1,2,3}couldberepresentedasthelist(2321322).Designprocedureselementof-set?,adjoin-set,unio

Exercise2.58Supposewewanttomodifythedifferentiationprogramsothatitworkswithordinarymathematicalnotation,inwhich+and*areinfixratherthanprefixoperators.Sincethedifferentiationprogramisdefinedintermsofabstractdata,we

Exercise2.56Showhowtoextendthebasicdifferentiatortohandlemorekindsofexpressions.Forinstance,implementthedifferentiationruled(x^n)/dx=nx^(n-1)byaddinganewclausetothederivprogramanddefiningappropriateproceduresexpone

Exercise2.52MakechangestothesquarelimitofwaveshowninFigure2.9byworkingateachofthelevelsdescribedabove.Inparticular:a.AddsomesegmentstotheprimitivewavepainterofExercise2.49(toaddasmile,forexample).b.Changethe

Exercise2.51Definethebelowoperationforpainters.belowtakestwopaintersasarguments.Theresultingpainter,givenaframe,drawswiththefirstpainterinthebottomoftheframeandwiththesecondpainterinthetop.Definebelowintwodiffere

Exercise2.50Definethetransformationflip-horiz,whichflipspaintershorizontally,andtransformationsthatrotatepainterscounterclockwiseby180degreesand270degrees.这道题挺有意思的，搞明白这道题就明白了frame的3个点的位置。如上图所示，为了更好

Exercise2.49Usesegments->paintertodefinethefollowingprimitivepainters:a.Thepainterthatdrawstheoutlineofthedesignatedframe.b.Thepainterthatdrawsan“X”byconnectingoppositecornersoftheframe.c.Thepainterthatdrawsad

Exercise2.48Adirectedlinesegmentintheplanecanberepresentedasapairofvectors—thevectorrunningfromtheorigintothestart-pointofthesegment,andthevectorrunningfromtheorigintotheend-pointofthesegment.Useyourvectorrepre

Exercise2.47Herearetwopossibleconstructorsforframes:(define(make-frameoriginedge1edge2)(listoriginedge1edge2))(define(make-frameoriginedge1edge2)(consorigin(consedge1edge2)))Foreachconstructorsupplytheappropriate

我在这一章遇到了一个大问题，就是书上用的那些函数beside,wave,flip-vert我统统用不了。我用的是DrRacket这个软件，在网上查了半天，终于找到了解决办法。首先是官方教程，在DrRacket中依次打开File->PackageManager...，在弹出的页面中"DoWhatIMean"菜单页的输入：sicp，

Exercise2.43LouisReasonerishavingaterribletimedoingExercise2.42.Hisqueensprocedureseemstowork,butitrunsextremelyslowly.(Louisneverdoesmanagetowaitlongenoughforittosolveeventhe6×6case.)WhenLouisasksEvaLuAtorf