tk.pratanumandal.expr4j.shuntingyard

Class ShuntingYardExpressionTree

java.lang.Object

tk.pratanumandal.expr4j.shuntingyard.ShuntingYard

tk.pratanumandal.expr4j.shuntingyard.ShuntingYardExpressionTree

public class ShuntingYardExpressionTree
extends ShuntingYard

The ShuntingYardExpressionTree class provides an implementation of the Shunting Yard algorithm using Expression Tree.

An expression tree is created from the postfix (or RPN) expression.
The expression tree is then parsed to evaluate the expression.

Since:

0.0.2

Author:

Pratanu Mandal

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
protected class	ShuntingYardExpressionTree.Node The Node class represents a node of the expression tree.

Field Summary

Fields

Modifier and Type	Field and Description
protected Stack<Operator>	operatorStack Stack to hold the operators.
protected Stack<Token>	postfix Stack to hold the postfix (RPN) expression.
protected ShuntingYardExpressionTree.Node	root Root node of the expression tree.

Constructor Summary

Constructors

Constructor and Description
ShuntingYardExpressionTree() No-Argument Constructor.

Method Summary

Modifier and Type	Method and Description
protected Operand	evaluate(ShuntingYardExpressionTree.Node node) Method to recursively evaluate the expression tree and return the result as an operand.
double	evaluate(String expr) Method to evaluate an expression. This method acts as the single point of access for expression evaluation.
protected void	evaluateParenthesis() Method to evaluate operators at the top of the operator stack until a left parenthesis is encountered.
protected void	formTree() Method to form the expression tree.
protected boolean	formTree(ShuntingYardExpressionTree.Node node, Token token) Method to form the expression tree recursively.
protected void	init(String expr) Method to create the postfix expression from the infix expression.

Methods inherited from class java.lang.Object

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

Field Detail

root

protected ShuntingYardExpressionTree.Node root

Root node of the expression tree.

postfix

protected Stack<Token> postfix

Stack to hold the postfix (RPN) expression.

operatorStack

protected Stack<Operator> operatorStack

Stack to hold the operators.

Constructor Detail

ShuntingYardExpressionTree

public ShuntingYardExpressionTree()

No-Argument Constructor.

Method Detail

init

protected void init(String expr)

Method to create the postfix expression from the infix expression.

Parameters:

expr - Expression string

evaluateParenthesis

protected void evaluateParenthesis()

Method to evaluate operators at the top of the operator stack until a left parenthesis is encountered.

formTree

protected boolean formTree(ShuntingYardExpressionTree.Node node,
                           Token token)

Method to form the expression tree recursively.

Parameters:

node - Current node of the expression tree

token - Token to be inserted

Returns:

true if token could be inserted, otherwise false

formTree

protected void formTree()

Method to form the expression tree.

evaluate

protected Operand evaluate(ShuntingYardExpressionTree.Node node)

Method to recursively evaluate the expression tree and return the result as an operand.

Parameters:

node - Current node of the expression tree

Returns:

Result of expression evaluation as an operand

evaluate

public double evaluate(String expr)

Method to evaluate an expression.
This method acts as the single point of access for expression evaluation.

Specified by:

evaluate in class ShuntingYard

Parameters:

expr - Expression string

Returns:

Result of expression evaluation as a double