edu.mit.ai.psg.jevaES
Class LeftAssociativeOperatorExpression

java.lang.Object
  |
  +--edu.mit.ai.psg.jevaES.SimpleNode
        |
        +--edu.mit.ai.psg.jevaES.JevaNode
              |
              +--edu.mit.ai.psg.jevaES.ExpressionNode
                    |
                    +--edu.mit.ai.psg.jevaES.LeftAssociativeOperatorExpression

Direct Known Subclasses:

JNEAdditiveExpression, JNEAndExpression, JNEEqualityExpression, JNEExclusiveOrExpression, JNEInclusiveOrExpression, JNEMultiplicativeExpression, JNERelationalExpression, JNEShiftExpression

public abstract class LeftAssociativeOperatorExpression

extends ExpressionNode

Shared implementation for left associative operators.

Author:

CarlManning, caroma@ai.mit.edu
Copyright (c) 1997 Massachusetts Institute of Technology

Fields inherited from class edu.mit.ai.psg.jevaES.SimpleNode

children, id, parent

Method Summary

abstract Object	binaryCombine(Token operator, Object accumResult, Object nextResult) binaryCombine -- combine two values, implemented in subclasses
abstract Class	binaryCombineTypes(Token operator, Class accumType, Class nextType) binaryCombineTypes -- Class of result of combining two types; implemented in subclasses
boolean	computeIsConstant(IEnv env)
Class	computeType(IEnv env)
Object	eval(IEnv env)

Methods inherited from class edu.mit.ai.psg.jevaES.ExpressionNode

getType, getValue, isConstant

Methods inherited from class edu.mit.ai.psg.jevaES.JevaNode

getBeginToken, getEndToken, print, print, printToken, printToString, printToString, setBeginToken, setEndToken

Methods inherited from class edu.mit.ai.psg.jevaES.SimpleNode

dump, jjtAddChild, jjtClose, jjtGetChild, jjtGetNumChildren, jjtGetParent, jjtOpen, jjtSetParent, toString, toString

Methods inherited from class java.lang.Object

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

Method Detail

computeType

public Class computeType(IEnv env)
                  throws VerifyingException

Returns:

Class of result returned by this operator on these arguments.

Throws:

IllegalTypeException - if types not acceptable

VerifyingException - if expression is illegal.

Overrides:

computeType in class ExpressionNode

binaryCombineTypes

public abstract Class binaryCombineTypes(Token operator,
                                         Class accumType,
                                         Class nextType)
                                  throws IllegalArgumentException

binaryCombineTypes -- Class of result of combining two types; implemented in subclasses

Parameters:

operator - is the Token between expressions (e.g., +,-,*,/,...)

accumResult - is result of accumulating the expressions to the left of the operator.

nextResult - is result of evaluating the next expression to the right of the operator.

Returns:

Class of result of the combining accumResult and nextResult with operator.

Throws:

IllegalArgumentException - if types not acceptable

computeIsConstant

public boolean computeIsConstant(IEnv env)
                          throws VerifyingException

Returns:

true if result of this expression is constant. Default is true if all subexpressions are constant, but subclasses may override this behavior.

Throws:

VerifyingException - if expression is illegal .

Overrides:

computeIsConstant in class ExpressionNode

eval

public Object eval(IEnv env)
            throws ThrowException

Returns:

evaluated children combined leftAssociatively, using binaryCombine()

Throws:

ThrowException - if expression completes abruptly with exception

Overrides:

eval in class ExpressionNode

binaryCombine

public abstract Object binaryCombine(Token operator,
                                     Object accumResult,
                                     Object nextResult)
                              throws ThrowException

binaryCombine -- combine two values, implemented in subclasses

Parameters:

operator - is the Token between expressions (e.g., +,-,*,/,...)

accumResult - is result of accumulating the expressions to the left of the operator.

nextResult - is result of evaluating the next expression to the right of the operator.

Returns:

result of the combining accumResult and nextResult with operator

Throws:

ThrowException - if expression completes abruptly with exception