[MWForum] state variables

[Wendy Petti]

There is another way to add and delete state variables in MW EX:

In the turtle's backpack, on the State tab, you can right-click on "I have"
and you'll get a menu from which you may select "Add."  Type the name of the
variable, click OK, and the name appears underneath "I have."  To assign a
value to the variable, double-click the name or else right-click its name
again and select "Edit," to open a "value" dialog box with empty brackets.
Type a value to replace the brackets.

To delete a variable, you may right-click its name on the State tab and
select "Remove."  Alternatively, on the Project tab you may click on the +
next to the turtle's name to reveal an icon, name, and value for each
variable assigned to that turtle.  Right-click the icon or name and select
"Remove."

As Daniel has pointed out, you may also create and remove a variable created
through "turtlesown" - this will add the same variable to every turtle in
the project, without assigning a value to the variable.  Here are some
demonstration commands that can be typed in the Command Center:

Example 1:

turtlesown "speed
t1, setspeed 5
t2, setspeed 3

Example 2:

turtlesown "speed
everyone [setspeed 1 + random 5]
end

(In the second example, a different randomly-chosen number from 1 - 5 is
assigned as the value for each turtle's speed variable.)

I suspect that most users of MW EX would prefer to the turtle's backpack
interface to create and remove variables when dealing with just one or two
turtles at a time, but a pair of turtlesown commands in the Command Center
can be an efficient way to address an "army" of turtles all at once.  For
instance, suppose you hatch 30 turtles and assign each of them a starting
shape, heading, and position.  You want to launch them into action, but you
want them to be able to return to their starting conditions.  It would be
very cumbersome to determine the precise starting conditions for each turtle
and write a procedure with a lengthy set of commands to restore the turtles
to these conditions.  But it can be done simply like this:

(in the Command Center)

turtlesown "startpos
everyone [setstartpos pos]
turtlesown "startheading
everyone [setstartheading heading]
turtlesown "startshape
everyone [setstartshape shape]

(in the Procedures tab)

to get-ready
everyone [setpos startpos
          setheading startheading
          setsh startshape]
end

To clarify the above commands using just one of them as an example:
everyone [setstartpos pos] means:  "I'm telling each turtle to check its
position (with "pos") and set the "startpos" variable to this value."  In
this particular case, each turtle's startpos value will be a list of its x
and y coordinates in brackets, such as
[100 -49]
The value of startheading will be a single number from 0 to 359.
The value of startshape will be a number if the shape is unnamed, or else it
will be the name of the shape.

The get-ready procedure tells each turtle to set its position, heading, and
shape to the values of the 3 variables previously created with the
turtlesown commands, whose values were set with the set(variablename)
commands.

Wendy


> > How do you delete a homebase or speed in the state tab?