slogo.instruction

Class Assignment

java.lang.Object

slogo.GrammarElement

slogo.instruction.Assignment

public class Assignment
extends GrammarElement

An assignment instruction assigns an expression to a variable, updating the global state to reflect the assignment.

Executing the assignment instruction causes the expression to be evaluated and assigned to the variable, until the assignment instruction executes, the expression isn't evaluated.

Field Summary

Fields

Modifier and Type	Field and Description
protected GrammarElement	myExpression
protected Variable	myVariable

Fields inherited from class slogo.GrammarElement

gelementsToValue

Constructor Summary

Constructors

Constructor and Description
Assignment(Variable v, GrammarElement e) Construct an Assignment instruction from a variable and an expression, e.g., X = expression.

Method Summary

Modifier and Type	Method and Description
java.lang.Object	evaluate(Context c) Evaluate the expression that's part of this instruction and update a global map/store to record the assignment of the expression to the variable.
java.lang.String	toString() Returns a String for this instruction.

Methods inherited from class java.lang.Object

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

Field Detail

myVariable

protected Variable myVariable

myExpression

protected GrammarElement myExpression

Constructor Detail

Assignment

public Assignment(Variable v,
                  GrammarElement e)

Construct an Assignment instruction from a variable and an expression, e.g., X = expression.

Parameters:

e - expression being assigned

v - variable to which the expression is assigned

Method Detail

evaluate

public java.lang.Object evaluate(Context c)

Evaluate the expression that's part of this instruction and update a global map/store to record the assignment of the expression to the variable.

Specified by:

evaluate in class GrammarElement

Parameters:

c - is the Context in which the evaluation takes place

Returns:

the result of evaluation (which is the expression assigned)

toString

public java.lang.String toString()

Returns a String for this instruction.

Overrides:

toString in class java.lang.Object

Returns:

VAR = EXPRESSION