[MWForum] state variables

[Wendy Petti]

P.S. A few more bits of information about creating and removing state
variables:

The TURTLESOWN method of creating state variables for all turtles in a
project can be used with any version of MicroWorlds.

You can remove such a variable in any version of MW by typing this in the
Command Center:

remove "variablename

If you have MW EX and check the State tab, you'll see that after typing this
command, the variable disappears from each turtle's backpack.  It also
disappears from the turtlesown listing on the Project tab, in MW EX and MW
Pro.  And it disappears from MW 2.0_ too even though there is no easy way to
"see" this.  So this is one more way to remove a state variable, through a
REMOVE command in the Command Center.

If you use the GIVETURTLE command to create a state variable for one
specific turtle (in MW Pro or EX), then you also have the option of removing
that turtle's state variable with a REMOVE command in the Command Center.

Wendy

> -----Original Message-----
> From: mwforum-admin@lists.mathcats.com
> [mailto:mwforum-admin@lists.mathcats.com]On Behalf Of Wendy Petti
> Sent: Thursday, April 21, 2005 2:16 PM
> To: mwforum@lists.mathcats.com
> Subject: RE: [MWForum] state variables
>
>
> 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?
>
>
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