slogo.instruction

Class Left

java.lang.Object

slogo.GrammarElement

slogo.instruction.Instruction

slogo.instruction.Left

public class Left
extends Instruction

A LEFT instruction has one component: a GrammarElement that represents the number of degrees to turn the turtle to the left. To evaluate a LEFT instruction the expression is evaluated first, this determines the double version of the degrees. The turtle's heading is then set using those degrees.

The value returned by evaluating a LEFT instruction is the expression itself, representing the degrees to turn the turtle to the left.

Field Summary

Fields

Modifier and Type	Field and Description
private GrammarElement	expression

Fields inherited from class slogo.GrammarElement

gelementsToValue

Constructor Summary

Constructors

Constructor and Description
Left(GrammarElement e) Constructs a LEFT instruction that can be executed.

Method Summary

Modifier and Type	Method and Description
java.lang.Object	evaluate(Context c) Evaluate this instruction in a Context.
java.lang.String	toString()

Methods inherited from class java.lang.Object

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

Field Detail

expression

private GrammarElement expression

Constructor Detail

Left

public Left(GrammarElement e)

Constructs a LEFT instruction that can be executed.

Parameters:

e - number of degrees to turn to the left

Method Detail

evaluate

public java.lang.Object evaluate(Context c)

Evaluate this instruction in a Context.

Specified by:

evaluate in class Instruction

Parameters:

c - the Context for the evaluation

Returns:

the degrees moved to the left

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object

Returns:

a String representing this instruction as LT, followed by the expression about the degrees turned to the left