elan.expression
Class Expression

java.lang.Object
  |
  +--elan.GrammarElement
        |
        +--elan.expression.Expression

Direct Known Subclasses:

Background, Bg, BinaryExpression, Heading, Number, Pc, Pencolor, Pendownp, Pensize, Ps, Shape, UnaryExpression, Variable, Xcor, Ycor

public abstract class Expression

extends GrammarElement

the base class of all arithmetic expressions, the evaluate method uses the hook/template method value to return a Double value, the template method returns a double.

Fields inherited from class elan.GrammarElement

functionMap, ourMap

Constructor Summary

Expression()

Method Summary

java.lang.Object	evaluate(Context c) Evaluate this language construct in some context.
abstract double	value(Context c)

Methods inherited from class java.lang.Object

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

Constructor Detail

Expression

public Expression()

Method Detail

evaluate

public java.lang.Object evaluate(Context c)

Description copied from class: GrammarElement

Evaluate this language construct in some context. The evaluation may have side-effects, e.g., moving a turtle.

Overrides:

evaluate in class GrammarElement

Following copied from class: elan.GrammarElement

Parameters:

is - the context in which the evaluation takes place

Returns:

the result of evaluating the construct

value

public abstract double value(Context c)