com.ds.common.expression

类 EvaluatorVisitor

java.lang.Object

com.ds.common.expression.EvaluatorVisitor

所有已实现的接口:

ParserVisitor

public class EvaluatorVisitor
extends Object
implements ParserVisitor

This class is used for the evaluation of an expression. It uses the Visitor design pattern to traverse the function tree and evaluate the expression using a stack.

Function nodes are evaluated by first evaluating all the children nodes, then applying the function class associated with the node. Variable and constant nodes are evaluated by pushing their value onto the stack.

构造器概要

构造器

构造器和说明
EvaluatorVisitor() Constructor.

方法概要

限定符和类型	方法和说明
Object	getValue(Node topNode, Vector errorList_in, SymbolTable symTab_in) Returns the value of the expression as an object.
Object	visit(ASTConstant node, Object data) Visit a constant node.
Object	visit(ASTFunNode node, Object data) Visit a function node.
Object	visit(ASTStart node, Object data) This method should never be called when evaluating a normal expression.
Object	visit(ASTVarNode node, Object data) Visit a variable node.
Object	visit(SimpleNode node, Object data) This method should never be called when evaluation a normal expression.

从类继承的方法 java.lang.Object

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

构造器详细资料

EvaluatorVisitor

public EvaluatorVisitor()

Constructor. Initialize the stack member

方法详细资料

getValue

public Object getValue(Node topNode,
                       Vector errorList_in,
                       SymbolTable symTab_in)
                throws Exception

Returns the value of the expression as an object. The expression tree is specified with its top node. The algorithm uses a stack for evaluation.

The errorList_in parameter is used to add error information that may occur during the evaluation. It is not required, and may be set to null if no error information is needed.

The symTab parameter can be null, if no variables are expected in the expression. If a variable is found, an error is added to the error list.

An exception is thrown, if an error occurs during evaluation.

返回:

The value of the expression as an object.

抛出:

Exception

visit

public Object visit(SimpleNode node,
                    Object data)

This method should never be called when evaluation a normal expression.

指定者:

visit 在接口中 ParserVisitor

visit

public Object visit(ASTStart node,
                    Object data)

This method should never be called when evaluating a normal expression.

指定者:

visit 在接口中 ParserVisitor

visit

public Object visit(ASTFunNode node,
                    Object data)

Visit a function node. The values of the child nodes are first pushed onto the stack. Then the function class associated with the node is used to evaluate the function.

指定者:

visit 在接口中 ParserVisitor

visit

public Object visit(ASTVarNode node,
                    Object data)

Visit a variable node. The value of the variable is obtained from the symbol table (symTab) and pushed onto the stack.

指定者:

visit 在接口中 ParserVisitor

visit

public Object visit(ASTConstant node,
                    Object data)

Visit a constant node. The value of the constant is pushed onto the stack.

指定者:

visit 在接口中 ParserVisitor