Fortran95程序设计\光盘\fortran95程序设计--光盘\document\FORTRAN95\c02

JUN1997WORKINGDRAFTJ3/97-0071Section2:Fortrantermsandconcepts22.1Highlevelsyntax3ThissectionintroducesthetermsassociatedwithprogramunitsandotherFortranconceptsabove4theconstruct,statement,andexpressionlevelsandillustratestheirrelationships.Thenotation5usedinthisstandardisdescribedin1.6.6NOTE2.17Someofthesyntaxrulesinthissectionaresubjecttoconstraintsthataregivenonlyatthe8appropriateplacesinlatersections.9R201programisprogram-unit10[program-unit]...11Aprogramshallcontainexactlyonemain-programprogram-unit.12R202program-unitismain-program13orexternal-subprogram14ormodule15orblock-data16R1101main-programis[program-stmt]17[specification-part]18[execution-part]19[internal-subprogram-part]20end-program-stmt21R203external-subprogramisfunction-subprogram22orsubroutine-subprogram23R1216function-subprogramisfunction-stmt24[specification-part]25[execution-part]26[internal-subprogram-part]27end-function-stmt28R1221subroutine-subprogramissubroutine-stmt29[specification-part]30[execution-part]31[internal-subprogram-part]32end-subroutine-stmt33R1104moduleismodule-stmt34[specification-part]35[module-subprogram-part]36end-module-stmt37R1112block-dataisblock-data-stmt38[specification-part]39end-block-data-stmt40R204specification-partis[use-stmt]...41[implicit-part]42[declaration-construct]...JUN1997WORKINGDRAFT9J3/97-007WORKINGDRAFTJUN19971R205implicit-partis[implicit-part-stmt]...2implicit-stmt3R206implicit-part-stmtisimplicit-stmt4orparameter-stmt5orformat-stmt6orentry-stmt7R207declaration-constructisderived-type-def8orinterface-block9ortype-declaration-stmt10orspecification-stmt11orparameter-stmt12orformat-stmt13orentry-stmt14orstmt-function-stmt15R208execution-partisexecutable-construct16[execution-part-construct]...17R209execution-part-constructisexecutable-construct18orformat-stmt19orentry-stmt20ordata-stmt21R210internal-subprogram-partiscontains-stmt22internal-subprogram23[internal-subprogram]...24R211internal-subprogramisfunction-subprogram25orsubroutine-subprogram26R212module-subprogram-partiscontains-stmt27module-subprogram28[module-subprogram]...29R213module-subprogramisfunction-subprogram30orsubroutine-subprogram31R214specification-stmtisaccess-stmt32orallocatable-stmt33orcommon-stmt34ordata-stmt35ordimension-stmt36orequivalence-stmt37orexternal-stmt38orintent-stmt39orintrinsic-stmt40ornamelist-stmt41oroptional-stmt42orpointer-stmt43orsave-stmt44ortarget-stmt45R215executable-constructisaction-stmt46orcase-construct47ordo-construct48orforall-construct49orif-construct10WORKINGDRAFTJUN1997JUN1997WORKINGDRAFTJ3/97-0071orwhere-construct2R216action-stmtisallocate-stmt3orassignment-stmt4orbackspace-stmt5orcall-stmt6orclose-stmt7orcontinue-stmt8orcycle-stmt9ordeallocate-stmt10orendfile-stmt11orend-function-stmt12orend-program-stmt13orend-subroutine-stmt14orexit-stmt15orforall-stmt16orgoto-stmt17orif-stmt18orinquire-stmt19ornullify-stmt20oropen-stmt21orpointer-assignment-stmt22orprint-stmt23orread-stmt24orreturn-stmt25orrewind-stmt26orstop-stmt27orwhere-stmt28orwrite-stmt29orarithmetic-if-stmt30orcomputed-goto-stmt31Constraint:Anexecution-partshallnotcontainanend-function-stmt,end-program-stmt,or32end-subroutine-stmt.332.2Programunitconcepts34ProgramunitsarethefundamentalcomponentsofaFortranprogram.Aprogramunitmaybea35mainprogram,anexternalsubprogram,amodule,orablockdataprogramunit.Asubprogram36maybeafunctionsubprogramorasubroutinesubprogram.Amodulecontainsdefinitionsthat37aretobemadeaccessibletootherprogramunits.Ablockdataprogramunitisusedtospecify38initialvaluesfordataobjectsinnamedcommonblocks.Eachtypeofprogramunitisdescribedin39Sections11or12.Anexternalsubprogramisasubprogramthatisnotinamainprogram,a40module,oranothersubprogram.Aninternalsubprogramisasubprogramthatisinamain41programoranothersubprogram.Amodulesubprogramisasubprogramthatisinamodulebut42isnotaninternalsubprogram.43Aprogramunitconsistsofasetofnonoverlappingscopingunits.Ascopingunitis44(1)Aderived-typedefinition(4.4.1),45(2)Aprocedureinterfacebody,excludinganyderived-typedefinitionsandprocedure46interfacebodiesinit(12.3.2.1),or47(3)Aprogramunitorsubprogram,excludingderived-typedefinitions,procedure48interfacebodies,andsubprogramsinit.49Ascopingunitthatimmediatelysurroundsanotherscopingunitiscalledthehostscopingunit.JUN1997WORKINGDRAFT11J3/97-007WORKINGDRAFTJUN199712.2.1Program2Aprogramconsistsofexactlyonemainprogramunitandanynumber(includingzero)ofother3kindsofprogramunits.Thesetofprogramunitsmayincludeanycombinationofthedifferent4kindsofprogramunitsinanyorderaslongasthereisonlyonemainprogramunit.5NOTE2.26Thereisarestrictionthatthereshallbenomorethanoneunnamedblockdataprogramunit7(11.4).8Sincethepublicportionsofamodulearerequiredtobeavailablebythetimeamodule9reference(11.3.1)isprocessed,aprocessormayrequireaspecificorderofprocessingofthe10programunits.112.2.2Mainprogram12Themainprogramisdescribedin11.1.132.2.3Procedure14Aprocedureencapsulatesanarbitrarysequenceofcomputationsthatmaybeinvokeddirectly15duringprogramexecution.Proceduresareeitherfunctionsorsubroutines.Afunctionisa16procedurethatisinvokedinanexpression;itsinvocationcausesavaluetobecomputedwhichis17thenusedinevaluatingtheexpression.Thevariablethatreturnsthevalueofafunctioniscalled18theresultvariable.AsubroutineisaprocedurethatisinvokedinaCALLstatementorbya19definedassignmentstatement(12.4,12.4.3,7.5.1.3).Unlessitisapureprocedure,asubroutinemay20beusedtochangetheprogramstatebychangingthevaluesofanyofthedataobjectsaccessibleto21thesubroutine;unlessitisapureprocedure,afunctionmaydothisinadditiontocomputingthe22functionvalue.23ProceduresaredescribedfurtherinSection12.242.2.3.1Externalprocedure25Anexternalprocedureisaprocedurethatisdefinedbyanexternalsubprogramorbymeansother26thanFortran.Anexternalproceduremaybeinvokedbythemainprogramorbyanyprocedureof27aprogram.282.2.3.2Moduleprocedure29Amoduleprocedureisaprocedurethatisdefinedbyamodulesubprogram(R213).Amodule30proceduremaybeinvokedbyanothermodulesubprograminthemoduleorbyanyscopingunit31thataccessesthemoduleprocedurebyuseassociation(11.3.2).Themodulecontainingthe32subprogramiscalledthehostofthemoduleprocedure.332.2.3.3Internalprocedure34Aninternalprocedureisaprocedurethatisdefinedbyaninternalsubprogram(R211).The35containingmainprogramorsubprogramiscalledthehostoftheinternalprocedure.Aninternal36procedureislocaltoitshostinthesensethattheinternalprocedureisaccessiblewithinthe37scopingunitsofthehostandallitsotherinternalproceduresbutisnotaccessibleelsewhere.382.2.3.4Procedureinterfaceblock39Thepurposeofaprocedureinterfaceblockistodescribetheinterfaces(12.3)toasetof40proceduresandtooptionallypermitthemtobeinvokedthrougheitherasinglegenericname,a41definedoperator,oradefinedassignment.Itdeterminestheformsofreferencethroughwhichthe42proceduresmaybeinvoked(12.4).12WORKINGDRAFTJUN1997JUN1997WORKINGDRAFTJ3/97-00712.2.4Module2Amodulecontains(oraccessesfromothermodules)definitionsthataretobemadeaccessibleto3otherprogramunits.Thesedefinitionsincludedataobjectdeclarations,typedefinitions,4proceduredefinitions,andprocedureinterfaceblocks.Thepurposeofamoduleistomakethe5definitionsitcontainsaccessibletoallotherprogramunitsthatrequestaccess.Ascopingunitin6anotherprogramunitmayrequestaccesstothedefinitionsinamodule.Modulesarefurther7describedinSection11.82.3Executionconcepts9EachFortranstatementisclassifiedaseitheranexecutablestatementoranonexecutablestatement.10Therearerestrictionsontheorderinwhichstatementsmayappearinaprogramunit,andcertain11executablestatementsmayappearonlyincertainexecutableconstructs.122.3.1Executable/nonexecutablestatements13Programexecutionisasequence,intime,ofcomputationalactions.Anexecutablestatementisan14instructiontoperformorcontroloneormoreoftheseactions.Thus,theexecutablestatementsof15aprogramunitdeterminethecomputationalbehavioroftheprogramunit.Theexecutable16statementsareallofthosethatmakeupthesyntacticclassofexecutable-construct.17Nonexecutablestatementsdonotspecifyactions;theyareusedtoconfiguretheprogram18environmentinwhichcomputationalactionstakeplace.Thenonexecutablestatementsareall19thosenotclassifiedasexecutable.Allstatementsinablockdataprogramunitshallbe20nonexecutable.Amoduleispermittedtocontainexecutablestatementsonlywithinasubprogram21inthemodule.22Table2.1Requirementsonstatementordering23PROGRAM,FUNCTION,SUBROUTINE,24MODULE,orBLOCKDATAstatement25USEstatements26IMPLICITNONE27PARAMETERIMPLICIT28statementsstatements29FORMATDerived-typedefinitions,30andPARAMETERinterfaceblocks,31ENTRYandDATAtypedeclarationstatements,32statementsstatementsspecificationstatements,andstatementfunctionstatements33DATAExecutable34statementsconstructs35CONTAINSstatement36Internalsubprograms37ormodulesubprograms38ENDstatement392.3.2Statementorder40ThesyntaxrulesofSection2.1specifythestatementorderwithinprogramunitsandsubprograms.41TheserulesareillustratedinTable2.1andTable2.2.Table2.1showstheorderingrulesfor42statementsandappliestoallprogramunitsandsubprograms.Verticallinesdelineatevarietiesof43statementsthatmaybeinterspersedandhorizontallinesdelineatevarietiesofstatementsthatshall44notbeinterspersed.InternalormodulesubprogramsshallfollowaCONTAINSstatement.JUN1997WORKINGDRAFT13J3/97-007WORKINGDRAFTJUN19971BetweenUSEandCONTAINSstatementsinasubprogram,nonexecutablestatementsgenerally2precedeexecutablestatements,althoughtheENTRYstatement,FORMATstatement,andDATA3statementmayappearamongtheexecutablestatements.Table2.2showswhichstatementsare4allowedinascopingunit.5Table2.2Statementsallowedinscopingunits6MainBlockExternalModuleInternalInterfaceKindofscopingunit:Module7programdatasubprogsubprogsubprogbody8USEstatementYesYesYesYesYesYesYes9ENTRYstatementNoNoNoYesYesNoNo10FORMATstatementYesNoNoYesYesYesNo11Misc.declarations(seenote)YesYesYesYesYesYesYes12DATAstatementYesYesYesYesYesYesNo13Derived-typedefinitionYesYesYesYesYesYesYes14InterfaceblockYesYesNoYesYesYesYes15ExecutablestatementYesNoNoYesYesYesNo16CONTAINSstatementYesYesNoYesYesNoNo17StatementfunctionstatementYesNoNoYesYesYesNo18NotesforTable2.2:1)Misc.declarationsarePARAMETERstatements,IMPLICITstatements,typedeclaration19statements,andspecificationstatements.2)Derivedtypedefinitionsarealsoscopingunits,buttheydonotcontainanyoftheabove20statements,andsohavenotbeenlistedinthetable.3)Thescopingunitofamoduledoesnotincludeanymodulesubprogramsthatthemodulecontains.212.3.3TheENDstatement22Anend-program-stmt,end-function-stmt,end-subroutine-stmt,end-module-stmt,orend-block-data-stmtis23anENDstatement.Eachprogramunit,modulesubprogram,andinternalsubprogramshallhave24exactlyoneENDstatement.Theend-program-stmt,end-function-stmt,andend-subroutine-stmt25statementsareexecutable,andmaybebranchtargetstatements.Executinganend-program-stmt26causesterminationofexecutionoftheprogram.Executinganend-function-stmtor27end-subroutine-stmtisequivalenttoexecutingareturn-stmtinasubprogram.28Theend-module-stmtandend-block-data-stmtstatementsarenonexecutable.292.3.4Executionsequence30Executionofaprogrambeginswiththefirstexecutableconstructofthemainprogram.The31executionofamainprogramorsubprograminvolvesexecutionoftheexecutableconstructswithin32itsscopingunit.Whenaprocedureisinvoked,executionbeginswiththefirstexecutableconstruct33appearingaftertheinvokedentrypoint.Withthefollowingexceptions,theeffectofexecutionis34asiftheexecutableconstructsareexecutedintheorderinwhichtheyappearinthemainprogram35orsubprogramuntilaSTOP,RETURN,orENDstatementisexecuted.Theexceptionsarethe36following:37(1)Executionofabranchingstatement(8.2)changestheexecutionsequence.These38statementsexplicitlyspecifyanewstartingplacefortheexecutionsequence.39(2)CASEconstructs,DOconstructs,andIFconstructscontainaninternalstatement40structureandexecutionoftheseconstructsinvolvesimplicitinternalbranching.See41Section8forthedetailedsemanticsofeachoftheseconstructs.42(3)END=,ERR=,andEOR=specifiersmayresultinabranch.43(4)Alternatereturnsmayresultinabranch.14WORKINGDRAFTJUN1997JUN1997WORKINGDRAFTJ3/97-0071InternalsubprogramsmayprecedetheENDstatementofamainprogramorasubprogram.The2executionsequenceexcludesallsuchdefinitions.32.4Dataconcepts4Nonexecutablestatementsareusedtodefinethecharacteristicsofthedataenvironment.This5includestypingvariables,declaringarrays,anddefiningnewdatatypes.62.4.1Datatype7Adatatypeisanamedcategoryofdatathatischaracterizedbyasetofvalues,togetherwitha8waytodenotethesevaluesandacollectionofoperationsthatinterpretandmanipulatethevalues.9Thiscentralconceptisdescribedin4.1.10Therearetwocategoriesofdatatypes:intrinsictypesandderivedtypes.112.4.1.1Intrinsictype12Anintrinsictypeisatypethatisdefinedimplicitly,alongwithoperations,andisalways13accessible.Theintrinsictypesareinteger,real,complex,character,andlogical.Thepropertiesof14intrinsictypesaredescribedin4.3.Anintrinsictypemaybeparameterized,inwhichcasetheset15ofdatavaluesdependsonthevaluesoftheparameters.Suchaparameteriscalledatype16parameter(4.3).ThetypeparametersareKINDandLEN.17Thekindtypeparameterindicatesthedecimalexponentrangefortheintegertype(4.3.1.1),the18decimalprecisionandexponentrangefortherealandcomplextypes(4.3.1.2,4.3.1.3),andthe19representationmethodsforthecharacterandlogicaltypes(4.3.2.1,4.3.2.2).Thecharacterlength20parameterspecifiesthenumberofcharactersforthecharactertype.212.4.1.2Derivedtype22Aderivedtypeisatypethatisnotdefinedimplicitlybutrequiresatypedefinitiontodeclare23componentsofintrinsicorofotherderivedtypes.Ascalarobjectofsuchaderivedtypeiscalled24astructure(5.1.1.7).Theonlyintrinsicoperationforderivedtypesisassignmentwithtype25agreement(7.5.1.5).Foreachderivedtype,structureconstructorsareavailabletoprovidevalues26(4.4.4).Inaddition,dataobjectsofderivedtypemaybeusedasprocedureargumentsandfunction27results,andmayappearininput/outputlists.Ifadditionaloperationsareneededforaderived28type,theyshallbesuppliedasproceduredefinitions.29Derivedtypesaredescribedfurtherin4.4.302.4.2Datavalue31Eachintrinsictypehasassociatedwithitasetofvaluesthatadatumofthattypemaytake.The32valuesforeachintrinsictypearedescribedin4.3.Becausederivedtypesareultimatelyspecified33intermsofcomponentsofintrinsictypes,thevaluesthatobjectsofaderivedtypemayassumeare34determinedbythetypedefinitionandthesetsofvaluesoftheintrinsictypes.352.4.3Dataentity36Adataentityisadataobject,theresultoftheevaluationofanexpression,ortheresultofthe37executionofafunctionreference(calledthefunctionresult).Adataentityhasadatatype(either38intrinsicorderived)andhas,ormayhave,adatavalue(theexceptionisanundefinedvariable).39Everydataentityhasarankandisthuseitherascalaroranarray.JUN1997WORKINGDRAFT15J3/97-007WORKINGDRAFTJUN199712.4.3.1Dataobject2Adataobject(oftenabbreviatedtoobject)isaconstant(4.1.2),avariable(6),orasubobjectofa3constant.Thetypeofanameddataobjectmaybespecifiedexplicitly(5)orimplicitly(5.3).4Subobjectsareportionsofcertainnamedobjectsthatmaybereferencedanddefined(variables5only)independentlyoftheotherportions.Theseincludeportionsofarrays(arrayelementsand6arraysections),portionsofcharacterstrings(substrings),andportionsofstructures(components).7Subobjectsarethemselvesdataobjects,butsubobjectsarereferencedonlybysubobject8designators.Asubobjectofavariableisavariable.SubobjectsaredescribedinSection6.9Objectsreferencedbyanameare:10anamedscalar(ascalarobject)11anamedarray(anarrayobject)12Subobjectsreferencedbyasubobjectdesignatorare:13anarrayelement(ascalarsubobject)14anarraysection(anarraysubobject)15astructurecomponent(ascalaroranarraysubobject)16asubstring(ascalarsubobject)172.4.3.1.1Variable18Avariablemayhaveavalueandmaybedefinedandredefinedduringexecutionofaprogram.192.4.3.1.2Constant20Aconstanthasavalueandcannotbecomedefinedorredefinedduringexecutionofaprogram.A21constantwithanameiscalledanamedconstantandhasthePARAMETERattribute(5.1.2.1).A22constantwithoutanameiscalledaliteralconstant(4.3).232.4.3.1.3Subobjectofaconstant24Asubobjectofaconstantisaportionofaconstant.Theportionreferencedmaydependonthe25valueofavariable.26NOTE2.327Forexample,given:28CHARACTER(LEN=10),PARAMETER::DIGITS='0123456789'29CHARACTER(LEN=1)::DIGIT30INTEGER::I31...32DIGIT=DIGITS(I:I)33DIGITSisanamedconstantandDIGITS(I:I)designatesasubobjectoftheconstantDIGITS.342.4.3.2Expression35Anexpression(7.1)producesadataentitywhenevaluated.Anexpressionrepresentseitheradata36referenceoracomputation,andisformedfromoperands,operators,andparentheses.Thetype,37value,andrankofanexpressionresultaredeterminedbytherulesinSection7.382.4.3.3Functionreference39Afunctionreference(12.4.2)producesadataentitywhenthefunctionisexecutedduring40expressionevaluation.Thetypeandrankofafunctionresultaredeterminedbytheinterfaceof41thefunction(12.2.2).Thevalueofafunctionresultisdeterminedbyexecutionofthefunction.16WORKINGDRAFTJUN1997JUN1997WORKINGDRAFTJ3/97-00712.4.4Scalar2Ascalarisadatumthatisnotanarray.Scalarsmaybeofanyintrinsictypeorderivedtype.3NOTE2.44Astructureisscalarevenifithasarraysascomponents.5Therankofascalariszero.Theshapeofascalarisrepresentedbyarank-onearrayofsizezero.62.4.5Array7Anarrayisasetofscalardata,allofthesametypeandtypeparameters,whoseindividual8elementsarearrangedinarectangularpattern.Anarrayelementisoneoftheindividualelements9inthearrayandisascalar.Anarraysectionisasubsetoftheelementsofanarrayandisitselfan10array.11Anarraymayhaveuptosevendimensions,andanyextent(numberofelements)inany12dimension.Therankofthearrayisthenumberofdimensions,anditssizeisthetotalnumberof13elements,whichisequaltotheproductoftheextents.Anarraymayhavezerosize.Theshapeof14anarrayisdeterminedbyitsrankanditsextentineachdimension,andmayberepresentedasa15rank-onearraywhoseelementsaretheextents.Allnamedarraysshallbedeclared,andtherank16ofanamedarrayisspecifiedinitsdeclaration.Therankofanamedarray,oncedeclared,is17constantandtheextentsmaybeconstantalso.However,theextentsmayvaryduringexecution18foradummyargumentarray,anautomaticarray,apointerarray,andanallocatablearray.19Twoarraysareconformableiftheyhavethesameshape.Ascalarisconformablewithanyarray.20Anyintrinsicoperationdefinedforscalarobjectsmaybeappliedtoconformableobjects.Such21operationsareperformedelement-by-elementtoproducearesultantarrayconformablewiththe22arrayoperands.Element-by-elementoperationmeanscorrespondingelementsoftheoperand23arraysareinvolvedina"scalar-like"operationtoproducethecorrespondingelementintheresult24array,andallsuchelementoperationsmaybeperformedinanyorderorsimultaneously.Suchan25operationisdescribedaselemental.26Arank-onearraymaybeconstructedfromscalarsandotherarraysandmaybereshapedintoany27allowablearrayshape(4.5).28Arraysmaybeofanyintrinsictypeorderivedtypeandaredescribedfurtherin6.2.292.4.6Pointer30ApointerisavariablethathasthePOINTERattribute.Apointerisassociatedwithatargetby31allocation(6.3.1)orpointerassignment(7.5.2).Apointershallneitherbereferencednordefined32untilitisassociated.ApointerisdisassociatedfollowingexecutionofaDEALLOCATEor33NULLIFYstatement,followingpointerassociationwithadisassociatedpointer,orinitiallythrough34pointerinitialization.Adisassociatedpointerisnotcurrentlyassociatedwithatarget(14.6.2).If35thepointerisanarray,therankisdeclared,buttheextentsaredeterminedwhenthepointeris36associatedwithatarget.372.4.7Storage38Manyofthefacilitiesofthisstandardmakenoassumptionsaboutthephysicalstorage39characteristicsofdataobjects.However,programunitsthatincludestorageassociationdependent40featuresshallobservecertainstorageconstraints(14.6.3).412.5Fundamentalterms42Thefollowingtermsaredefinedhereandusedthroughoutthisstandard.JUN1997WORKINGDRAFT17J3/97-007WORKINGDRAFTJUN199712.5.1Nameanddesignator2Anameisusedtoidentifyaprogramconstituent,suchasaprogramunit,namedvariable,named3constant,dummyargument,orderivedtype.Therulesgoverningtheconstructionofnamesare4givenin3.2.1.Asubobjectdesignatorisanamefollowedbyoneormoreofthefollowing:5componentselectors,arraysectionselectors,arrayelementselectors,andsubstringselectors.62.5.2Keyword7Thetermkeywordisusedintwowaysinthisstandard.Awordthatispartofthesyntaxofa8statementisastatementkeyword.Thesekeywordsarenotreservedwords;thatis,nameswith9thesamespellingsareallowed.Examplesofstatementkeywordsare:IF,READ,UNIT,KIND,and10INTEGER.11Anargumentkeywordisadummyargumentname(12.4).Section13specifiesargument12keywordsforalloftheintrinsicprocedures.Argumentkeyw