Module Simula

Package simula.compiler.syntaxClass.expression

Class Expression

java.lang.Object

simula.compiler.syntaxClass.SyntaxClass

simula.compiler.syntaxClass.expression.Expression

Direct Known Subclasses:

ArithmeticExpression, AssignmentOperation, BooleanExpression, ConditionalExpression, Constant, LocalObject, ObjectGenerator, ObjectRelation, QualifiedObject, RelationalOperation, RemoteVariable, TextExpression, TypeConversion, UnaryOperation, VariableExpression

public abstract sealed class Expression
extends SyntaxClass
permits VariableExpression, ArithmeticExpression, AssignmentOperation, BooleanExpression, ConditionalExpression, Constant, LocalObject, ObjectGenerator, ObjectRelation, QualifiedObject, RelationalOperation, RemoteVariable, TextExpression, TypeConversion, UnaryOperation

Expression.

 Simula Standard: Chapter 3 Expressions
 
   expression
      = value-expression
      | reference-expression
      | designational-expression
      
   value-expression
      = arithmetic-expression
      | Boolean-expression
      | character-expression
      
   reference-expression
      = object-expression
      | text-expression
 

Syntax used during Parsing:

 Expression  =  SimpleExpression
                   |  IF  BooleanExpression  THEN  SimpleExpression  ELSE  Expression

  SimpleExpression  =  BooleanTertiary  { OR ELSE  BooleanTertiary }
  BooleanTertiary   =  Equivalence  { AND THEN  Equivalence }
  Equivalence       =  Implication  { EQV  Implication }
  Implication       =  BooleanTerm  { IMP  BooleanTerm }
  BooleanTerm       =  BooleanFactor  { OR  BooleanFactor }
  BooleanFactor     =  BooleanSecondary  { AND  BooleanSecondary }
  BooleanSecondary  =  [ NOT ]  BooleanPrimary
  BooleanPrimary    =  TextPrimary  { & TextPrimary }
  TextPrimary       =  SimpleArithmeticExpression  [ RelationOperator  SimpleArithmeticExpression ]
       RelationOperator  =  <  |  <=  |  =  |  >=  |  >  |  <> |  ==  |  =/=
  SimpleArithmeticExpression  =  [ + | - ]  Term  {  ( + | - )  Term }
  Term    =  Factor  {  ( * | / | // )  Factor }
  Factor  =  BasicExpression  { **  BasicExpression }
              
  
  BasicExpression  =  PrimaryExpression  |  {  RemoteIdentifier  |  ObjectRelation  |  QualifiedObject   }
                RemoteIdentifier =  PrimaryExpression  .  AttributeIdentifier
                ObjectRelation   =  PrimaryExpression ( IS | IN )  ClassIdentifier
                QualifiedObject  =  PrimaryExpression  QUA  ClassIdentifier
 
  PrimaryExpression =  ( Expression ) | Constant | ObjectGenerator | LocalObject | Variable | SubscriptedVariable
                Constant = IntegerConstant | RealConstant | CharacterConstant | TextConstant | BooleanConstant | SymbolicValue  
                                BooleanConstant = TRUE | FALSE
                                SymbolicValue   = NONE | NOTEXT
                ... other constants as delivered by the scanner
                ObjectGenerator  =  NEW  Identifier  "("  Expression  {  ,  Expression  }  ")"
                LocalObject = THIS ClassIdentifier
                Variable  =  Identifier
                SubscriptedVariable  =  Identifier  "("  Expression  {  ,  Expression  }  ")"
   
 

Link to GitHub: Source File.

Author:

SIMULA Standards Group, Øystein Myhre Andersen, Stein Krogdahl

Field Summary

Fields

Modifier and Type	Field	Description
SyntaxClass	backLink	This Expression is part of backLink Expression/Statement.
Type	type	The type

Fields inherited from class simula.compiler.syntaxClass.SyntaxClass

lineNumber

Constructor Summary

Constructors

Constructor	Description
Expression()	Expression.

Method Summary

Modifier and Type	Method	Description
private static Expression	acceptAdditiveOperation()	Parse Utility: Accept additive operation.
private static Expression	acceptAND()	Parse Utility: Accept Boolean AND.
private static Expression	acceptANDTHEN()	Parse Utility: Accept Boolean AND THEN.
private static Expression	acceptBASICEXPR()	Parse basic expression.
private static Expression	acceptEQV()	Parse Utility: Accept Boolean EQV.
private static Expression	acceptEXPON()	Parse Utility: Accept exponentiation.
static Expression	acceptExpression()	Accept expression.
private static Expression	acceptIMP()	Parse Utility: Accept Boolean IMP.
private static Expression	acceptMULDIV()	Parse Utility: Accept multiplicative operation.
private static Expression	acceptNOT()	Parse Utility: Accept Boolean NOT.
private static Expression	acceptOR()	Parse Utility: Accept Boolean OR.
private static Expression	acceptRelation()	Parse Utility: Accept relation.
private static Expression	acceptSimpleExpression()	Parse simple expression.
private static Expression	acceptTEXTCONC()	Parse Utility: Accept text concatenation.
private static Expression	acceptUNIMULDIV()	Parse Utility: Accept unary plus and minus.
static boolean	checkCompatibility(Expression simpleObjectExpression, String classIdentifier)	Check compatibility between simpleObjectExpression and a classDeclaration.
Expression	evaluate()	Try to Compile-time Evaluate this expression
static Expression	expectExpression()	Expect expression.
private static VariableExpression	expectVariable()	Parse Utility: Expect Variable
protected String	get()	Generate code for getting the value of this Expression
int	getInt()	Try to evaluate this expression to an integer.
Number	getNumber()	Try to evaluate this expression to a number.
static ClassDeclaration	getQualification(String classIdentifier)	Get qualification.
private static ClassDeclaration	getQualification(Expression expr)	Returns the qualification of the given simpleObjectExpression.
VariableExpression	getWriteableVariable()	Get a writeable variable.
abstract boolean	maybeStatement()	Returns true if this expression may be used as a statement.
void	printTree(int indent)	Utility print syntax tree method.
(package private) String	put(String evaluated)	Generate code for putting the value into this Expression
String	toString()

Methods inherited from class simula.compiler.syntaxClass.SyntaxClass

ASSERT_SEMANTICS_CHECKED, doChecking, doDeclarationCoding, doJavaCoding, edIndent, edTreeIndent, IS_SEMANTICS_CHECKED, print, SET_SEMANTICS_CHECKED, toJavaCode

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Details

type

public Type type

The type

backLink

public SyntaxClass backLink

This Expression is part of backLink Expression/Statement.

Constructor Details

Expression

Expression()

Expression.

Method Details

toString

public String toString()

Overrides:

toString in class Object

acceptExpression

public static Expression acceptExpression()

Accept expression.

 Expression  =  SimpleExpression
                 |  IF  BooleanExpression  THEN  SimpleExpression  ELSE  Expression
 

Returns:

Expression or null if no expression is found.

expectExpression

public static Expression expectExpression()

Expect expression.

 Expression  =  SimpleExpression
                 |  IF  BooleanExpression  THEN  SimpleExpression  ELSE  Expression
 

If no expression is found an error message is printed.

Returns:

Expression or null if no expression is found.

acceptSimpleExpression

private static Expression acceptSimpleExpression()

Parse simple expression.

  SimpleExpression  =  BooleanTertiary  { OR ELSE  BooleanTertiary }
  BooleanTertiary   =  Equivalence  { AND THEN  Equivalence }
  Equivalence       =  Implication  { EQV  Implication }
  Implication       =  BooleanTerm  { IMP  BooleanTerm }
  BooleanTerm       =  BooleanFactor  { OR  BooleanFactor }
  BooleanFactor     =  BooleanSecondary  { AND  BooleanSecondary }
  BooleanSecondary  =  [ NOT ]  BooleanPrimary
  BooleanPrimary    =  TextPrimary  { & TextPrimary }
  TextPrimary       =  SimpleArithmeticExpression  [ RelationOperator  SimpleArithmeticExpression ]
       RelationOperator  =  <  |  <=  |  =  |  >=  |  >  |  <> |  ==  |  =/=
  SimpleArithmeticExpression  =  [ + | - ]  Term  {  ( + | - )  Term }
  Term    =  Factor  {  ( * | / | // )  Factor }
  Factor  =  BasicExpression  { **  BasicExpression }
 

Returns:

Expression or null if no expression is found.

acceptANDTHEN

private static Expression acceptANDTHEN()

Parse Utility: Accept Boolean AND THEN.

 BooleanTertiary =  Equivalence  { AND THEN  Equivalence }
 

Returns:

an expression

acceptEQV

private static Expression acceptEQV()

Parse Utility: Accept Boolean EQV.

 Equivalence  =  Implication  { EQV  Implication }
 

Returns:

an expression

acceptIMP

private static Expression acceptIMP()

Parse Utility: Accept Boolean IMP.

 Implication =  BooleanTerm  { IMP  BooleanTerm }
 

Returns:

an expression

acceptOR

private static Expression acceptOR()

Parse Utility: Accept Boolean OR.

 BooleanTerm  =  BooleanFactor  { OR  BooleanFactor }
 

Returns:

an expression

acceptAND

private static Expression acceptAND()

Parse Utility: Accept Boolean AND.

 BooleanFactor =  BooleanSecondary  { AND  BooleanSecondary }
 

Returns:

an expression

acceptNOT

private static Expression acceptNOT()

Parse Utility: Accept Boolean NOT.

 BooleanSecondary  =  [ NOT ]  BooleanPrimary
 

Returns:

an expression

acceptTEXTCONC

private static Expression acceptTEXTCONC()

Parse Utility: Accept text concatenation.

 BooleanPrimary  =  TextPrimary  { & TextPrimary }
 

Returns:

an expression

acceptRelation

private static Expression acceptRelation()

Parse Utility: Accept relation.

 TextPrimary =  SimpleArithmeticExpression  [ RelationOperator  SimpleArithmeticExpression ]
    RelationOperator  =  <  |  <=  |  =  |  >=  |  >  |  <> |  ==  |  =/=
 

Returns:

an expression

acceptAdditiveOperation

private static Expression acceptAdditiveOperation()

Parse Utility: Accept additive operation.

 SimpleArithmeticExpression  =  UnaryTerm  {  ( + | - )  Term }
 

Returns:

an expression

acceptUNIMULDIV

private static Expression acceptUNIMULDIV()

Parse Utility: Accept unary plus and minus.

 UnaryTerm  =  [ + | - ]  Term
 

Returns:

an expression

acceptMULDIV

private static Expression acceptMULDIV()

Parse Utility: Accept multiplicative operation.

 Term  =  Factor  {  ( * | / | // )  Factor }
 

Returns:

an expression

acceptEXPON

private static Expression acceptEXPON()

Parse Utility: Accept exponentiation.

 Factor  =  BasicExpression  { **  BasicExpression }
 

Returns:

an expression

acceptBASICEXPR

private static Expression acceptBASICEXPR()

Parse basic expression.

  BasicExpression  =  PrimaryExpression  |  {  RemoteIdentifier  |  ObjectRelation  |  QualifiedObject   }
                RemoteIdentifier =  PrimaryExpression  .  AttributeIdentifier
                ObjectRelation   =  PrimaryExpression ( IS | IN )  ClassIdentifier
                QualifiedObject  =  PrimaryExpression  QUA  ClassIdentifier
 
  PrimaryExpression =  ( Expression ) | Constant | ObjectGenerator | LocalObject | Variable | SubscriptedVariable
                Constant = IntegerConstant | RealConstant | CharacterConstant | TextConstant | BooleanConstant | SymbolicValue  
                                BooleanConstant = TRUE | FALSE
                                SymbolicValue   = NONE | NOTEXT
                ... other constants as delivered by the scanner
                ObjectGenerator  =  NEW  Identifier  "("  Expression  {  ,  Expression  }  ")"
                LocalObject = THIS ClassIdentifier
                Variable  =  Identifier
                SubscriptedVariable  =  Identifier  "("  Expression  {  ,  Expression  }  ")"
 

Returns:

Expression or null if no expression is found.

expectVariable

private static VariableExpression expectVariable()

Parse Utility: Expect Variable

 Variable  =  Identifier  |  SubscriptedVariable
        SubscriptedVariable  =  Identifier  "("  Expression  {  ,  Expression  }  ")"
 

NOTE: That a SubscriptedVariable may be an subscripted array or a function designator.

Returns:

the created Variable

getWriteableVariable

public VariableExpression getWriteableVariable()

Get a writeable variable.

This method is redefined in Variable, RemoteVariable and TypeConversion

Returns:

a writeable variable or null

getQualification

private static ClassDeclaration getQualification(Expression expr)

Returns the qualification of the given simpleObjectExpression.

Parameters:

expr - simpleObjectExpression

Returns:

the qualification of the given simpleObjectExpression

getQualification

public static ClassDeclaration getQualification(String classIdentifier)

Get qualification.

Parameters:

classIdentifier - a class identifier

Returns:

the ClassDeclaration with same identifier

checkCompatibility

public static boolean checkCompatibility(Expression simpleObjectExpression,
 String classIdentifier)

Check compatibility between simpleObjectExpression and a classDeclaration.

Parameters:

simpleObjectExpression - a simple object expression

classIdentifier - a class identifier

Returns:

true if compatible, otherwise false

evaluate

public Expression evaluate()

Try to Compile-time Evaluate this expression

Returns:

the resulting evaluated expression

maybeStatement

public abstract boolean maybeStatement()

Returns true if this expression may be used as a statement.

Returns:

true if this expression may be used as a statement

get

protected String get()

Generate code for getting the value of this Expression

Returns:

the resulting Java code

put

String put(String evaluated)

Generate code for putting the value into this Expression

Parameters:

evaluated - a evaluated expression.

Returns:

the resulting Java code

getNumber

public Number getNumber()

Try to evaluate this expression to a number.

Returns:

the resulting number or null

getInt

public int getInt()

Try to evaluate this expression to an integer.

Returns:

the resulting int or 0

printTree

public void printTree(int indent)

Description copied from class: SyntaxClass

Utility print syntax tree method.

Overrides:

printTree in class SyntaxClass

Parameters:

indent - number of spaces leading the lines