slogo.instruction

Class Minus

java.lang.Object

slogo.GrammarElement

slogo.instruction.Instruction

slogo.instruction.Minus

public class Minus
extends Instruction

A MINUS instruction has one component: a GrammarElement that represents the number to return the negative of. To evaluate a MINUS instruction the expression is evaluated first, this determines the double version. The number multiplied by negative one is returned.

The value returned by evaluating a MINUS instruction is the expression itself, representing the number.

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
Minus(GrammarElement e) Constructs a MINUS 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

Minus

public Minus(GrammarElement e)

Constructs a MINUS instruction that can be executed.

Parameters:

e - number to take the opposite of

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 number*-1

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object

Returns:

a String representing this instruction as MINUS, followed by the expression