slogo.instruction

Class Sum

java.lang.Object

slogo.GrammarElement

slogo.instruction.Instruction

slogo.instruction.Sum

public class Sum
extends Instruction

A SUM instruction has two components: two GrammarElements that represents the two numbers to perform addition on. To evaluate a SUM instruction the expressions are evaluated first, this determines the double version of the numbers. The second number is added to the first and the result is returned.

The value returned by evaluating a SUM instruction is the instruction itself, followed by the two expressions

Field Summary

Fields

Modifier and Type	Field and Description
private GrammarElement	expressionOne
private GrammarElement	expressionTwo
private java.lang.Double	total

Fields inherited from class slogo.GrammarElement

gelementsToValue

Constructor Summary

Constructors

Constructor and Description
Sum(GrammarElement e, GrammarElement f) Constructs a DIFFERENCE 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

expressionOne

private GrammarElement expressionOne

expressionTwo

private GrammarElement expressionTwo

total

private java.lang.Double total

Constructor Detail

Sum

public Sum(GrammarElement e,
           GrammarElement f)

Constructs a DIFFERENCE instruction that can be executed.

Parameters:

e - the first number

f - the second number

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 total after addition

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object

Returns:

a String representing this instruction as SUM, followed by the two expressions