编译原理-数据类型和类型检查

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1、Chapter6DataTypesandTypeCheckingInstructorJianhuiYueSoftwareCollege@SCUcompilerscu@21cn.comCompilerTheoryFall2003JianhuiYuePrincipalTaskofCompilerTypeinference-thecomputationandmaintenanceofinformationondatatypesTypechecking–theuseoftheinformationtoensurethateachpartoftheprogr

2、ammakessenseunderthetyperulesofthelanguage.Thesetwotasksarerelated,performedtogether,andreferredastypechecking.CompilerTheoryFall2003JianhuiYueDataTypeDatatypeissetofvalueswithcertainoperationsonthosevalues.Example:integerreferstoasubsetofthemathematicalintegers,togetherwithth

3、earithmeticoperationsthatareprovidedbythelanguagedefinition.Datatypesaredescribedbyatypeexpressions,whichisAtypename(suchasinteger)orAstructuredexpressions(suchasarray[10])OperationsareassumedorimpliedCompilerTheoryFall2003JianhuiYueTypeExpressionsTypeexpressionscanoccurinseve

4、ralplacesinaprogram.Explicittypeinformationintx;-associatesatypetoavariablenameclassCar{…}–definesanewtypenameImplicittypeinformationconstgreeting=“Hello!”;-arrayofcharinPascal.Typeinformation,thatiscontainedindeclarations,ismaintainedinthesymboltableandretrievedbythetypecheck

5、erwhenevertheassociatednamesarereferenced.Example:a[i].Arangecheckingisnotstaticallydeterminable.CompilerTheoryFall2003JianhuiYueSimpleTypesTherearebuild-in(predefined)typesinaprogramminglanguage.Example:intanddoubleThepredefinedtypescorrespondtoNumericdatatypesthatareprovided

6、bymachinearchitecturesandwhoseoperationsexistasmachineinstructions.Elementarytypeslikebooleanorcharwhosebehavioriseasytoimplement.Suchdatatypesaresimpletypes,theirvalueshavenointernalstructure.CompilerTheoryFall2003JianhuiYueNewSimpleDataTypesInsomeprogramminglanguagesitisposs

7、ibletodefinenewsimpletypes.typedefenum{red,green,blue}Color;CompilerTheoryFall2003JianhuiYueStructuredTypesGivenasetofpredefinedtypes,newdatatypescanbecreatedusingtypeconstructors,suchasarrayandstruct.Suchtypesareoftencalledstructuredtypes.Arraysarecommonlyallocatedcontiguouss

8、toragefromsmallertolargerindexes.CompilerTheoryFall2003Jianhu