LIVAALiteVersionofJava

ShanqiLu JiafeiSong ZihanJiao YananZhangsl4017 js4984 zj2203 yz3054

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Table of Contents

CHAPTER1INTRODUCTION....................................................................................................3

CHAPTER2LEXICALCONVENTIONS........................................................................................32.1WhiteSpace...............................................................................................................................32.2Comments..................................................................................................................................42.3Identifiers...................................................................................................................................42.4Keyword.....................................................................................................................................42.5Literals.......................................................................................................................................4

2.5.1BooleanLiterals..........................................................................................................................42.5.2IntegerLiterals............................................................................................................................52.5.3FloatingPointLiterals.................................................................................................................52.5.4CharacterLiterals........................................................................................................................52.5.5StringLiterals..............................................................................................................................52.5.6EscapeSequencesforCharacterandStringLiterals...................................................................52.5.7TheNullLiteral............................................................................................................................6

2.6Separators..................................................................................................................................62.7Operators...................................................................................................................................6

CHAPTER3Types....................................................................................................................63.1PrimitiveTypes...........................................................................................................................6

3.1.1IntegralTypes.............................................................................................................................63.1.2Floating-PointTypes...................................................................................................................73.1.3TheBooleanType.......................................................................................................................7

3.2ReferenceTypes.........................................................................................................................73.2.1Objects........................................................................................................................................73.2.2TheClassString...........................................................................................................................73.2.3Arrays..........................................................................................................................................8

CHAPTER4Classes.................................................................................................................84.1ClassDeclarations.......................................................................................................................84.2ClassMembers...........................................................................................................................94.3FieldDeclarations.......................................................................................................................94.4MethodDeclarations..................................................................................................................94.5ConstructorDeclarations............................................................................................................94.5Inheritance...............................................................................................................................10

CHAPTER5Statements..........................................................................................................105.1ExpressionStatements.............................................................................................................105.2DeclarationStatements............................................................................................................115.3ControlFlowStatements..........................................................................................................11

5.3.1If-thenandIf-then-else.............................................................................................................115.3.2Looping:for...............................................................................................................................125.3.3Looping:while...........................................................................................................................12

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5.4MethodCreationandMethodCall............................................................................................135.5PrinttoConsole........................................................................................................................145.6EmptyStatement......................................................................................................................15

CHAPTER6Expressions.........................................................................................................156.1Evaluation,Denotation,andResult...........................................................................................156.2TypeofanExpression...............................................................................................................166.3EvaluationOrder......................................................................................................................16

6.3.1Left-HandOperandFirst...........................................................................................................166.3.2EvaluateOperandsbeforeOperation.......................................................................................166.3.3EvaluationRespectsParenthesesandPrecedence..................................................................16

6.4LexicalLiterals..........................................................................................................................166.5TheArithmeticOperations.......................................................................................................176.6TheRelationalOperations........................................................................................................176.7TheBitwiseandConditionalOperations:..................................................................................186.8MethodInvocationExpressions................................................................................................186.9ArrayAccessExpressions..........................................................................................................186.10Assignment.............................................................................................................................19

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CHAPTER 1 INTRODUCTION LivaisageneralpurposeprogramminglanguageandaliteversionofJava.Itisdesignedtoletprogrammers who are familiar with class-based languages feel comfortable with developingcommonalgorithmslikeGCD.ItisliteinthesensethatitmaintainssomebutnotallfeaturesinJava. It has the similar syntax and abstract data types in Java and supports object-orientedparadigmandinheritance.However,genericsandnestedclassesarebeyondthescopeofthisproject,hencetheyarenottobeimplemented.The Liva programming language is strongly typed. The compiler checks whether argumentspassedtoafunctionmatchexpectedtypesandreturnanerrorifnot.ItisaportablelanguageandcompileddowntoLLVM.Thislanguagereferencemanualisorganizedasfollows:

• Chapter2describesthelexicalconventionsoftheLivaprogramminglanguage.• Chapter 3 describes types. Types are divided into two categories: primitive types and

referencetypes.• Chapter4describesclassesincludingclassdeclarationsandinheritance.• Chapter5describesstatements.• Chapter6describesexpressions.

CHAPTER 2 LEXICAL CONVENTIONS ThischapterspecifiesthelexicalconventionsofLivaprogramminglanguage.Acompilertakesaprogramwhichconsistsofasequenceofcharactersandreduceittoasequenceofelements,which are tokens,white space and comments. The tokens are identifiers, keywords, literals,separators,andoperators.

Element:WhiteSpace|Comment|Token

Token:Identifier|Keyword|Literal|Separator|Operator

2.1WhiteSpace

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White space in Liva is defined as space character, tab character, form feed character(page-breaking)andlineterminatorcharacter.Whitespacecharactersareignoredbyacompilerexceptastheyservetoseparatetokens.2.2CommentsThereisonekindofcomments:

• /*text*/Allcharactersfrom“/*”to“*/”areignored.2.3IdentifiersAnidentifierisasequenceofletters,digitsandunderscore‘_’.Itcanonlybeginwithaletter.Identifiersarethenamesofvariables,methodsandclasses.Theyarecase-sensitive.2.4KeywordKeywordsarereservedandcannotbeusedasidentifiers.

• Keyword:

2.5LiteralsLiteralsaresyntacticrepresentationsofnumeric,character,booleanorstringdata.Theyareusedforrepresentingvaluesinprograms.2.5.1BooleanLiteralsTherearetwobooleanliterals:

• true representsatrueBooleanvalue• false representsafalseBooleanvalue

for new if boolean this break

double implements else import return extendsint char interface void class float

while

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2.5.2IntegerLiteralsInteger numbers in Liva are in decimal format. Negative decimal numbers such as -10 areactuallyexpressionsconsistingoftheoperator‘-’andintegerliteral.Theprimitivetypeofintegerliteralisint.2.5.3FloatingPointLiteralsFloatingpointnumbersareexpressedasdecimalfractionsandconsistof:

• anoptional‘+’or‘-’sign;ifomitted,thevalueispositive,• oneofthefollowingformats

Format Example

integerdigits 9integerdigits . 7.integerdigits . integerdigits 17.31 . integerdigits .56

2.5.4CharacterLiteralsCharacterliteralsareexpressedasasinglequote:'a', '#', 'π'2.5.5StringLiteralsStringliteralsbeginwithadoublequotecharacter",followedbyzeroormorecharactersandaterminatingdoublequote"Withinstringliterals,therecanbeescapesequencesbutnotunescapednewline.2.5.6EscapeSequencesforCharacterandStringLiteralsAnescapesequenceisusedtorepresentaspecialcharacter.Itbeginswithabackslashcharacter(\),whichindicatesthatthefollowingcharactersshouldbetreatedspecially.Escapesequencesarelistedinthetablebelow.Name CharacterTAB \tnewline \ndoublequote \”singlequote \’backslash \\

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2.5.7TheNullLiteralNullisaspecialliteralwhichrepresentsanullvaluewhichdoesnotrefertoanyobject.Thenullliteralisformedas:null2.6SeparatorsSeparatorsaretokensusedforseparatingtokens.

2.7OperatorsTheexpressionsectionofthismanualwillexplainbehaviorsoftheseoperators.Herelistsalltheoperators.

CHAPTER 3 Types TheLivaprogramminglanguagesupportstwokindsoftypes:primitivetypesandreferencetypes.Therearealsotwokindsofdatavalues:primitivevaluesandreferencevaluesaccordingly.Thereisalsoaspecialnulltype.Primitivetypesarebooleantypesandnumerictypes.Referencetypesareclasstypesandarraytypes3.1PrimitiveTypesPrimitivetypesareredefinedandtheirnamesarereservedkeywords.3.1.1IntegralTypes

= > < ! == >=

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Theintegraltypesareintandchar.Theintegerdatatypeisa32-bitsequenceofdigits,whichhasaminimumvalueof-2^31andamaximumvalueof 2^31-1.An integer literal is a sequenceof digits precededby anoptionalnegativesign.Asinglezerocannotbeprecededbyanegativesign.

Thechardatatypebelongstointegraltypeswhosevaluesare16-bitunsignedintegers.

3.1.2Floating-PointTypesThefloating-pointdatatypeisasigned-precision32-bitformatvalues.

3.1.3TheBooleanTypeThebooleandata type has twopossible values:trueandfalse. A boolean is its own type andcannotbecomparedtoanon-booleanvariable.Therefore,expression“true==1”wouldleadtoanerror.

3.2ReferenceTypesTherearetwokindsofreferencetypes:classtypesandarraytypes.3.2.1ObjectsAnobjectcanbeaclassinstanceoranarray.3.2.2TheClassString

int x = 10; int y = -50; int z = 0;

char x = 'a';

float x = 1.5; float y = -5.1; float z = 2.0;

boolean x = true; boolean y = false;

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AninstanceofclassStringisasequenceofcharacters.TheclassStringsupportsthefollowingbuilt-inmethods:

• charAt(intindex)ThismethodreturnsthecharacterlocatedattheString'sspecifiedindexbutreturnsanerroriftheindexisoutofrange.Indexesstartfromzero.• length()Thismethodreturnsthelengthofastring.

3.2.3ArraysArrayscanbeseenasaspecialtype.Anarrayobjectcontainsanumberofvariables.Allelementsinanarraysmusthavethesametype.

CHAPTER 4 Classes Aclassdeclarationdefinesanewreferencetypeandhowitisimplemented.Classescontainfieldsandmethods. Field declarations describe class variables whilemethod declarations describeprogramsthatmaybeinvokedbyotherprograms4.1ClassDeclarationsClasses are defined in the following way. The optional extends clause in a class declarationspecifiesthesuperclassofthecurrentclass.

classMyClassextendsSuperClass{//field,constructor//methoddeclarations

}

String w = "Liva"; String x = new String("Liva"); int y = x.length(); char z = x.charAt(1);

int[] ai; char ac[] = { 'a', 'b', 'c', ' ' };

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4.2ClassMembersMembersofaclassconsistof:

• Membersinheritedfromitssuperclass• Membersdeclaredintheclassdeclaration

4.3FieldDeclarationsFieldDeclarationsspecifyvariablesofaclasstype.4.4MethodDeclarationsMethoddeclarationsspecifyexecutablecodethatmightbeinvoked.

4.5ConstructorDeclarationsIftheconstructorisnotdefined,thecompilergeneratesadefaultone.

/* Field declarations and method declarations */ class Calculation{ int z; void addition(int x, int y){ z = x+y; } void Subtraction(int x,int y){ z = x-y; } }

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4.5InheritanceInheritanceisthatasubclassacquiresallthebehaviorsandpropertiesofasuperclass.

CHAPTER 5 Statements Statements include: if, else, for, break, continue, return, as well all expressions which areexplainedinthefollowing.Exceptasindicated,statementsareexecutedinsequence5.1ExpressionStatementsAnexpressionstatementconsistsofanexpressionfollowedbyasemicolon.

/* User defined constructor*/ class Calculation{ int z; constructor (int z){ this.z = z; } void addition(int x, int y){ z = x+y; } void Subtraction(int x,int y){ z = x-y; } }

expression;

class My_Calculation extends Calculation { void multiplication(int x, int y) { z = x * y; } }

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Usuallyexpressionstatementsareassignmentsorfunctioncalls.

5.2DeclarationStatements Adeclarationstatementdeclaresavariablebyspecifyingitsdatatypeandname.Italsocouldinitializethevariableduringthedeclaring.

5.3ControlFlowStatements 5.3.1If-thenandIf-then-elseTherearetwoformsofconditionalstatements.For the first case, the conditional expression that is evaluated is enclosed in balancedparentheses. The sectionof code that is conditionally executed is specified as a sequenceofstatementsenclosedinbalancedbraces.Iftheconditionalexpressionevaluatestofalse,controljumpstotheendoftheif-thenstatement.

/* declare a variable with data type and name */ char a; int b =10; float c; int array1[] = { 2, 5, -2, 6, -3, 8, 0, -7, -9, 4 }; String name= "class"; boolean isMatch = false;

/* Object creation expressions */ Student e1 = new Student (); /* Object creation expressions */ c = 8933.234;

if (expression) { statement

}

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Inthesecondcasethesecondsub-statementisexecutediftheexpressionisfalse.Asusualthe‘else’ambiguityisresolvedbyconnectinganelsewiththelastencounteredelselessif.

5.3.2Looping:for The‘for’conditionwillalsoruninaloopsolongastheconditionspecifiedinthe‘for’statementistrue.The‘for’statementhasthefollowingformat:

Thefirstexpressionspecifiesinitializationfortheloopanditisexecutedonceatthebeginningofthe'for'statement;thesecondspecifiesatest,madebeforeeachiteration,suchthattheloopisterminated when the expression becomes false; the third expression typically specifies anincrementordecreasewhichisperformedaftereachiteration.Thefollowingexampleusesa‘for’statementtoprintthenumbersfrom0to10:

5.3.3Looping:whileThe‘while’statementhastheform:

The‘while’statementwillbeexecutedinaloopaslongasthespecifiedconditioninthewhilestatementistrue.Theexpressionmusthavetypeboolean,oracompile-timeerroroccurs.

if (expression) { statement1

} else { Statement2

}

for (expression1; expression2; expression 3) { statement

}

for (int num=0; num < 11; num ++) { print(num); }

while(expression) { statement

}

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• Ifthevalueforexpressionistrue,thenthecontainedstatementisexecuted

• Ifexecutionofthestatementcompletesnormally,thentheentire‘while’statementisexecutedagain,beginningbyre-evaluatingtheexpression.

• Ifthevalueoftheexpressionisfalse,nofurtheractionistakenandthe‘while’statementcompletesnormally.

5.3.4Branching:break,continue,andreturn Thebreakstatementcausesterminationofthesmallestenclosingforstatement;controlpassestothestatementfollowingtheterminatedstatement.Theexpressionfor ‘break’statement isshownbelow:

Thecontinuestatementcausescontroltopasstotheloop-continuationportionofthesmallestenclosingforstatement;thatistotheendoftheloop.Theexpressionfor‘continue’statementisshowbelow:

Afunctionreturnstoitscallerbymeansofthe‘return’statement,whichhasoneoftheforms:

Inthefirstcasenovalueisreturnedwhenamethodisdeclaredvoid.Forthefirstcase,theuserscouldspecifynoreturnstatementforsimplification.Inthesecondcase,simplyputthevalue(oran expression that calculates the value) after the return Keyword, then the value of theexpressionisreturnedtothecallerofthefunction. 5.4MethodCreationandMethodCall Theusercouldwritetheuser-definedmethods.

break;

continue;

return; return(expression);

returnType nameOfMethod (Parameter List) { // method body }

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• returnType: Methodmayreturnavalue. • nameOfMethod: Thisisthemethodname.Themethodsignatureconsistsofthemethod

nameandtheparameterlist. • Parameter List: The list of parameters, it is the type, order, and number of

parametersofamethod.Theseareoptional,methodmaycontainzeroparameters. • method body: Themethodbodydefineswhatthemethoddoeswithstatements.

Forusingamethod, it shouldbe called. Thereare twoways inwhichamethod is called i.e.methodreturnsavalueorreturningnothing(noreturnvalue).Following is the example to demonstrate how to define amethod and how to call itwith areturnedvalue:

5.5PrinttoConsole Theprint()functiontakesoneormoreparametersandprintsthemonebyonetostandardoutput.Theparametertypemaybestring,number,orobject.Itisinthefollowingform:

Hereisanexampletoacceptanintandprinttheinttotheconsole.

Anotherexampletoacceptastringandprintthestringtotheconsole:

void main(String[] args) { int a = 11; int b = 6; int c = minFunction(a, b); prin("Minimum Value = " + c); } int minFunction(int n1, int n2) { int min; if (n1 > n2) min = n2; else min = n1; return min; }

print (parameters);

print (1);

print (“CS4115 is fun!”)

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5.6EmptyStatement Anemptystatementdoesnothingandhasthefollowingform:

CHAPTER 6 Expressions Much of the work in a program is done by evaluatingexpressions, such as assignments tovariables,orfortheirvalues,whichcanbeusedasargumentsoroperandsinlargerexpressions,ortoaffecttheexecutionsequenceinstatements,orboth.

Thischapterspecifiesthemeaningsofexpressionsandtherulesfortheirevaluation.

6.1Evaluation,Denotation,andResultLivaevaluatesalargerexpressionbyevaluatingsmallerpartsofit.Sotheresultofanexpressionisimportant.Whenanexpressioninaprogramisevaluated(executed),theresultdenotesoneofthreethings:

• Avariable• Avalue• Nothing(forvoidfunctionsandmethods)

Anexpressiondenotesnothingifandonlyifitisamethodinvocationthatinvokesamethodthatdoesnotreturnavalue,thatis,amethoddeclaredvoid.Suchanexpressioncanbeusedonlyasan expression statement (in statement chapter), because every other context in which anexpressioncanappearrequirestheexpressiontodenotesomething.

Ifanexpressiondenotesavariable,andavalueisrequiredforuseinfurtherevaluation,thenthevalueofthatvariableisused.Inthiscontext,iftheexpressiondenotesavariableoravalue,wemayspeaksimplyofthevalueoftheexpression.Inthisway,wemaysayeachexpressiondenotesavalueinacertaintype.

;

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6.2TypeofanExpressionForanexpressionthatdenotestoavariable,thevaluestoredinavariableisalwayscompatiblewiththetypeofthevariable.Inotherwords,thevalueofanexpressionwhosetypeisTisalwayssuitableforassignmenttoavariableoftypeT.

The rules for determining the type of an expression that denotes to a value are explainedseparatelybelowforeachkindofexpression.Includingarithmeticoperations,relationoperations,bitwise/conditionaloperations,assignment.

6.3EvaluationOrder

Livaguaranteesthattheoperandsofoperatorsappeartobeevaluatedinaspecificevaluationorder,namely,fromlefttoright.

6.3.1Left-HandOperandFirst

Theleft-handoperandofabinaryoperatorappearstobefullyevaluatedbeforeanypartoftheright-handoperandisevaluated.

6.3.2EvaluateOperandsbeforeOperation

Liva guarantees that every operand of an operator (except the conditional operators&,|)appearstobefullyevaluatedbeforeanypartoftheoperationitselfisperformed.

Forexample,inanassignmentexpression,theassignmentwillnotbeevaluateduntiltherighthandoperands(ifitisanotherexpression)isevaluated.

6.3.3EvaluationRespectsParenthesesandPrecedence

Liva respects the order of evaluation indicated explicitly by parentheses and implicitly byoperatorprecedence.

6.4LexicalLiterals

Aliteraldenotesafixed,unchangingvalue.Thiskindofexpressioncouldbeevaluatedwithoutbeingbrokenintosmallexpressions.

Thetypeofaliteralisdeterminedasfollows:

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• Thetypeofanintegerliteralisint.• Thetypeofafloating-pointisfloat.• Thetypeofabooleanliteralisboolean.• Thetypeofacharacterliteralischar.• ThetypeofastringliteralisString.• Thetypeofthenullliteralnullisthenulltype;itsvalueisthenullreference.Evaluationofalexicalliteralalwayscompletesnormally.

6.5TheArithmeticOperationsThevalueofanequalityexpression isnumeric(intordouble,dependsontheoperands).Theoperators+,-,*,/,and%arecalledthearithmeticoperators.Theyhavethesameprecedenceand are syntactically left-associative (they group left-to-right). The type of the arithmeticexpressionisthepromotedtypeofitsoperands.

Thetypeofeachoftheoperandsofarithmeticoperatorsmustbeatypethatisconvertibletoaprimitivenumerictype,oracompile-timeerroroccurs.Forexample:“+”twoobjectsofauser-definedclassisprohibited.

+ Adds values on either side of the operator

- Subtracts right hand operand from left hand operand

* Multiplies values on either side of the operator

/ Divides left hand operand by right hand operand

% Divides left hand operand by right hand operand and returns remainder

6.6TheRelationalOperationsThevalueofanequalityexpressionisalwaysboolean.Theequalityoperatorsmaybeusedtocomparetwooperandsthatareconvertibletonumericinttype,ortwooperandsoftypeboolean.Allothercasesresultinacompile-timeerror.

== ( Addition) Adds values on either side of the operator

!= Checks if the values of two operands are equal or not, if values are not equal then condition becomes true.

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6.7TheBitwiseandConditionalOperations:UnlikeJava,Livauses&,|,^,~forbothbitwiseandconditionaloperations.Thatdependsontheoperands.TheoperandsofaBitwise/ConditionalOperationshouldbothbeintorboolean.

& Binary AND if both operands are int type / Logic AND if both operands are boolean type

| Binary OR if both operands are int type / Logic OR if both operands are boolean type

^ Binary XOR if both operands are int type / Logic XOR if both operands are boolean type

~ Binary Complement if both operands are int type / Logic INVERT if both operands are boolean type

6.8MethodInvocationExpressionsAmethod/function invocation expression is used to invoke an instancemethod (declared inpreviouschapters).Theresulttypeofthechosenmethodisdeterminedasfollows:Ifthechosenmethod/functionisdeclaredwithareturntypeofvoid,thentheresultisvoid.Otherwise,theresulttypeisthemethod/function'sdeclaredreturntype.

6.9ArrayAccessExpressionsAnarrayaccessexpressioncontainstwosubexpressions,thearrayreferenceexpression(beforetheleftbracket)andtheindexexpression(withinthebrackets).

Notethatthearrayreferenceexpressionmaybeanameoranyprimaryexpressionthatisnotan

> Checks if the value of left operand is greater than the value of right operand, if yes then condition becomes true.

< Checks if the value of left operand is less than the value of right operand, if yes then condition becomes true.

>= Checks if the value of left operand is greater than or equal to (no less than) the value of right operand, if yes then condition becomes true.

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arraycreationexpression.Thetypeofthearrayreferenceexpressionmustbeanarraytype.Fortheindexexpression,thepromotedtypemustbeint,oracompile-timeerroroccurs.

TheresultofanarrayaccessexpressionisavariableoftypeT,namelythevariablewithinthearrayselectedbythevalueoftheindexexpression.

6.10AssignmentInLiva,theonlyassignmentoperatoris“=”.

Theresultofthefirstoperandofanassignmentoperatormustbeavariable.Thisoperandmaybeanamedvariable,suchasalocalvariableorafieldofthecurrentobjectorclass,oritmaybeacomputedvariable,ascanresultfromafieldaccessoranarrayaccess(definedpreviously).