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Class edu.mit.ai.psg.jevaES.LeftAssociativeOperatorExpression 

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

Method Index

o binaryCombine(Token, Object, Object)
binaryCombine -- combine two values, implemented in subclasses
o binaryCombineTypes(Token, Class, Class)
binaryCombineTypes -- Class of result of combining two types; implemented in subclasses
o computeIsConstant(IEnv)
o computeType(IEnv)
o eval(IEnv)

Methods

o eval 
 public Object eval(IEnv env) throws EvalException
Returns:
evaluated children combined leftAssociatively, using binaryCombine()
Throws: EvalException
.
Overrides:
eval in class ExpressionNode
o 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
wraps exception thrown by operator.
o computeType 
 public Class computeType(IEnv env) throws EvalException
Returns:
Class of result returned by this operator on these arguments.
Throws: EvalException
.
Overrides:
computeType in class ExpressionNode
o binaryCombineTypes 
 public abstract Class binaryCombineTypes(Token operator,
                                          Class accumType,
                                          Class nextType)
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.
o computeIsConstant 
 public boolean computeIsConstant(IEnv env) throws EvalException
Returns:
true if result of this expression is constant. Default is true if all subexpressions are constant, but subclasses may override this behavior.
Throws: EvalException
.
Overrides:
computeIsConstant in class ExpressionNode 
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