com.threerings.expr
Class ExpressionParser<T>

java.lang.Object
  com.threerings.expr.ExpressionParser<T>

public class ExpressionParser<T>
extends Object

Parses simple expressions using an implementation of the shunting-yard algorithm.

Nested Class Summary

protected static class	ExpressionParser.ArrayIndex An array index identifier.
protected static class	ExpressionParser.FunctionCall An function call identifier.
protected static class	ExpressionParser.Identifier Wraps a string to identify it as an identifier.
protected static class	ExpressionParser.Operator An operator identifier.
protected static class	ExpressionParser.OperatorStreamTokenizer Extends StreamTokenizer slightly to handle multi-character operators.

Field Summary

protected Stack<Object>	_operation The operation stack.
protected Stack<T>	_output The output stack.
protected ExpressionParser.OperatorStreamTokenizer	_strtok The tokenizer from which we acquire tokens.
protected static Map<String,ExpressionParser.Operator>	OPERATORS The operator map.
protected static Map<String,ExpressionParser.Operator>	UNARY_ALTERNATES

Constructor Summary

ExpressionParser(Reader reader)
Creates a new parser to read from the specified reader.

Method Summary

protected static void	addOperator(String name, boolean rightAssociative, int precedence, int arity) Adds an operator to the map.
protected static void	addUnaryAlternate(String name, boolean rightAssociative, int precedence, int arity) Adds an unary alternate for operators that can be both unary and binary.
protected void	handle(Object value) Handles the supplied output value.
protected T	handleArrayIndex(String array) Handles an array index.
protected T	handleFunctionCall(String function, int arity) Handles a function call.
protected T	handleIdentifier(String name) Handles an identifier.
protected T	handleNumber(double value) Handles a number.
protected T	handleOperator(String operator, int arity) Handles an operator.
protected T	handleString(String value) Handles a string.
static void	main(String... args) Main method for testing.
T	parse() Parses the expression and returns the object at the top of the stack (or null if the stack is empty).

Methods inherited from class java.lang.Object

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

Field Detail

_strtok

protected ExpressionParser.OperatorStreamTokenizer _strtok

The tokenizer from which we acquire tokens.

_output

protected Stack<T> _output

The output stack.

_operation

protected Stack<Object> _operation

The operation stack.

OPERATORS

protected static final Map<String,ExpressionParser.Operator> OPERATORS

The operator map.

UNARY_ALTERNATES

protected static final Map<String,ExpressionParser.Operator> UNARY_ALTERNATES

Constructor Detail

ExpressionParser

public ExpressionParser(Reader reader)

Creates a new parser to read from the specified reader.

Method Detail

main

public static void main(String... args)
                 throws Exception

Main method for testing.

Throws:

Exception

parse

public T parse()
        throws Exception

Parses the expression and returns the object at the top of the stack (or null if the stack is empty).

Throws:

Exception

handle

protected void handle(Object value)
               throws Exception

Handles the supplied output value.

Throws:

Exception

handleNumber

protected T handleNumber(double value)
                  throws Exception

Handles a number.

Throws:

Exception

handleString

protected T handleString(String value)
                  throws Exception

Handles a string.

Throws:

Exception

handleOperator

protected T handleOperator(String operator,
                           int arity)
                    throws Exception

Handles an operator.

Throws:

Exception

handleFunctionCall

protected T handleFunctionCall(String function,
                               int arity)
                        throws Exception

Handles a function call.

Throws:

Exception

handleArrayIndex

protected T handleArrayIndex(String array)
                      throws Exception

Handles an array index.

Throws:

Exception

handleIdentifier

protected T handleIdentifier(String name)
                      throws Exception

Handles an identifier.

Throws:

Exception

addOperator

protected static void addOperator(String name,
                                  boolean rightAssociative,
                                  int precedence,
                                  int arity)

Adds an operator to the map.

addUnaryAlternate

protected static void addUnaryAlternate(String name,
                                        boolean rightAssociative,
                                        int precedence,
                                        int arity)

Adds an unary alternate for operators that can be both unary and binary.