net.sourceforge.webcompmath.awt
Class ExpressionInput.EI

java.lang.Object
  net.sourceforge.webcompmath.awt.ExpressionInput.EI

All Implemented Interfaces:

java.io.Serializable, Expression, Value

Enclosing class:

ExpressionInput

protected class ExpressionInput.EI
extends java.lang.Object
implements Expression

The expression associated with an ExpressionInput belongs to this class. So is any derivative of such a function. Note that derivatives must be recomputed when the expression changes. This is done via "lazy evaluation", that is, only when necessary. When a derivative is used, it tests whether it is out of date by comparing its serialNumber to the serial number of the expression that it is the derivative of. If they don't match, then the expression is recomputed and the serial number is updated. The serial number and defintion of the main expresssion is changed by checkInput() whenever the user's input has changed.

See Also:

Serialized Form

Method Summary

boolean	dependsOn(Variable x) Get whether this expression depends on a particular variable
Expression	derivative(Variable wrt) Get the derivative of the expression
double	getVal() Returns the value of the expression
double	getValueWithCases(Cases c) Returns the value of the expression
java.lang.String	toString() Convert the expression to a string

Methods inherited from class java.lang.Object

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

Method Detail

getVal

public double getVal()

Returns the value of the expression

Specified by:

getVal in interface Value

Returns:

the value

getValueWithCases

public double getValueWithCases(Cases c)

Returns the value of the expression

Specified by:

getValueWithCases in interface Expression

Parameters:

c - the cases to use

Returns:

the value

toString

public java.lang.String toString()

Convert the expression to a string

Specified by:

toString in interface Expression

Overrides:

toString in class java.lang.Object

Returns:

the string

derivative

public Expression derivative(Variable wrt)

Get the derivative of the expression

Specified by:

derivative in interface Expression

Parameters:

wrt - variable with respect to

Returns:

the derivative

dependsOn

public boolean dependsOn(Variable x)

Get whether this expression depends on a particular variable

Specified by:

dependsOn in interface Expression

Parameters:

x - the valiable to check

Returns:

true or false