uchicago.src.sim.math
Class CEquation

java.lang.Object
  uchicago.src.sim.math.CEquation

public class CEquation
extends java.lang.Object

A user specifiable evaluatable equation. This class will evaluate a specified equation replacing the variables in the equation with values from a specified object. The result of the equation evaluation will then be written to the object.

When evaluated a CEquation will replace the variables in the specified equation with those read from a specified object. For example, if the equation is "x + 1 * z", then evaluation will replace x and z in the equation with the results of calling getX() and getZ() on the object. The result of this evaluation will be assigned to the a resultVar in a similar manner. For example, if the resultVar is "y", then on assignment the result of the equation evaluation will be assigned to the object via the object's setY(double) method.

The variable "t" can also be used. "t" is replaced by the value of the current tick count. Similarly, the variable "dt" can be used. It will be set to the delta of the current tick count and the tick count at which the last evaluation occured.

Evaluation is performed using the evaluate method and assignment is performed using the assign method.

Version:

$Revision: 1.11 $ $Date: 2005/08/12 16:13:29 $

Author:

Nick Collier

Constructor Summary

CEquation(java.lang.Object target, TickCounter counter, java.lang.String equation, java.lang.String resultVar)
Creates a CEquation from the specified parameters.

CEquation(java.lang.Object target, TickCounter counter, java.lang.String equation, java.lang.String resultVar, double initialDTValue)
Creates a CEquation from the specified parameters.

Method Summary

void	assign() Assigns the result of the last call to evaluate to the result variable of the target specified in the constructor.
void	evaluate() Evaluates the equation encapsulated by this CEquation.
void	evaluateAndAssign() Evaluates the currently encapsulated equation and assigns the result to the result variable.
java.lang.String	getEquation()
void	setEquation(java.lang.String equation) Sets the equation to evalute.

Methods inherited from class java.lang.Object

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

Constructor Detail

CEquation

public CEquation(java.lang.Object target,
                 TickCounter counter,
                 java.lang.String equation,
                 java.lang.String resultVar)

Creates a CEquation from the specified parameters. When evaluated the CEquation will replace the variables in the specified equation with those read from the specified target. For example, if the equation is "x + 1 * z", then evaluation will replace x and z in the equation with the results of calling getX() and getZ() on the target. The result of this evaluation will be assigned to the specified resultVar in a similar manner. For example, if the resultVar is "y", then on assignment the result of the equation evaluation will be assigned to the target via a setY(double) method.

The variable "t" can also be used. "t" is replaced by the value of the current tick count. Similarly, the variable "dt" can be used. It will be set to the delta of the current tick count and the tick count at which the last evaluation occured. dt defaults to a value of 0 on the first evaluation. Use the alternate constructor to specify a different initial value.

Evaluation is performed using the evaluate method and assignment is performed using the assign method.

Parameters:

target - the target from which the equations variable values are read and to which the result is assigned

counter - a TickCounter from which the value of the "t" variable can be set

equation - the equation to evaluate.

resultVar - the name of the variable to assign the result to

CEquation

public CEquation(java.lang.Object target,
                 TickCounter counter,
                 java.lang.String equation,
                 java.lang.String resultVar,
                 double initialDTValue)

Creates a CEquation from the specified parameters. When evaluated the CEquation will replace the variables in the specified equation with those read from the specified target. For example, if the equation is "x + 1 * z", then evaluation will replace x and z in the equation with the results of calling getX() and getZ() on the target. The result of this evaluation will be assigned to the specified resultVar in a similar manner. For example, if the resultVar is "y", then on assignment the result of the equation evaluation will be assigned to the target via a setY(double) method.

The variable "t" can also be used. "t" is replaced by the value of the current tick count. Similarly, the variable "dt" can be used. It will be set to the delta of the current tick count and the tick count at which the last evaluation occured.

Evaluation is performed using the evaluate method and assignment is performed using the assign method.

Parameters:

target - the target from which the equations variable values are read and to which the result is assigned

counter - a TickCounter from which the value of the "t" variable can be set

equation - the equation to evaluate.

resultVar - the name of the variable to assign the result to

initialDTValue - the initial value of dt to use on the first evaluation when it would otherwise be set to 0

Method Detail

evaluate

public void evaluate()

Evaluates the equation encapsulated by this CEquation. This does NOT assign the result to the variable specified in the constructor. To assign the result to the result variable, follow the evaluate() call with a call to assign() or alternatively call evaluateAndAssign().

See Also:

assign(), evaluateAndAssign()

assign

public void assign()

Assigns the result of the last call to evaluate to the result variable of the target specified in the constructor.

evaluateAndAssign

public void evaluateAndAssign()

Evaluates the currently encapsulated equation and assigns the result to the result variable.

getEquation

public java.lang.String getEquation()

Returns:

the equation currently encapsulated and evaluated by this CEquation.

setEquation

public void setEquation(java.lang.String equation)

Sets the equation to evalute.

Parameters:

equation -