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Documentation .doc.features

Selecting Turtles

There can only be one turtle selected at any time. There can also be no selected turtle. To select a turtle, you click on the turtle's drawing with the left mouse button. When a turtle is selected, it shows a second black board around the original blue or red border. To select no turtles, left-click the mouse anywhere in the window where these is no turtle.

Turtles And The Clipboard

You may copy and paste turtles to and from the clipboard just like any other Windows program. When a turtle is copied to the clipboard, using the Copy command in the Edit menu, both textual and graphical data are placed on the clipboard. This means that you can edit the program of the turtle, which is placed on the clipboard as text data. It also means that you can paste the picture that the turtle draws into any graphics program, such as PhotoShop or Illustrator.

The textual data will contain the logo algorithm used by the turtle to draw its figure. This data can then be pasted into any text editor, or other application that utilizes text. Further, this textual data may be pasted back into any selected turtle to replace its algorithm (and thus its figure) with that represented by the algorithm on the clipboard. To try this, select a turtle, select Copy, select a different turtle, finally, select Paste.

The graphical data contains the Windows standard MetaFile data that draws the turtle's image. This MetaFile data can be pasted into any application that accepts MetaFile data. This allows you to paste a turtle's figure into any windows graphics application. Technically, the format of the data is the Windows Enhanced MetaFile.

Zooming In On A Turtle's Figure

To display a turtle's figure in the full area of the population window (to blow it up), simply right-click on the turtle's figure.

This will cause the turtle to display its figure full size in the contents of the population window. To return to viewing the entire population, left-click anywhere within the contents of the window, and the entire population will be displayed once again.

Doping Turtles

Doping a turtle means to replace its algorithm with another. This causes the turtle to display a figure that you select. This can be accomplished with the algorithm from a previously saved turtle, or it could be an algorithm that you have copied and modified, or it could be an algorithm that you have manufactured yourself using the Logo language.

Doping a turtle from a previously saved turtle is accomplished via the Load Turtle command in the File menu. This command is only highlighted when a turtle is selected. When you select the command, the Open File Dialog will be displayed asking you to select a file, which contains a previously saved turtle. Once you select a file, this file's turtle algorithm will replace the algorithm of the selected turtle, and the new figure will be drawn in the selected turtle's square.

Doping a turtle from an algorithm in textual form is accomplished via the Paste command in the Edit menu. When the Paste command is selected, it will look on the Clipboard for textual data. If textual data is found, it is assumed to be an expression using the logo language. If this turns out to be true, and the algorithm is syntactically correct (meaning there are no mistakes in the expression), then the currently selected turtle will have its algorithm replaced with the algorithm from the clipboard and a new figure will be drawn for the turtle. If the algorithm is not valid, then the application will display an error message, and leave the selected turtle unmodified.

Mutating Turtles

Mutating turtles involves randomly generating a logo expression and then randomly splicing this expression into the algorithm of the turtle. This can have a wide range of effects, from no visual difference, to profound visual change including no display at all.

Mutating a turtle is accomplished by selecting the turtle's figure then selecting the Mutate Turtle item in the File menu. This will cause the mutation to be made to the selected turtle, and its new figure to be displayed in its square.

Mutation is usually used when a population appears to be stuck in a particular feature set and it is proving difficult to move the population into any new directions without the injection of some random figures.

Note that sometimes when you mutate a turtle, the figure that it draws will not change. This is normal. It means that the mutation occurred in a part of the program that does not display, or in a portion where the modifications are not significant. Some turtles will never change what they draw without many mutations. Others will suddenly drawing nothing.

Printing Turtles

You may print a turtle's figure to any Windows supported printer. To print a turtle select the desired turtle's figure, then select the Print Turtle command from the File menu.

You can select Landscape mode for turtles whose drawings are wide.

When you print a turtle, you will first be presented with a dialog box asking you for the pen width. This is the width of the pen that will draw the turtle's figure. After you print several turtles, you will begin to note some significant differences with what you see on the screen. One of the primary differences will be the pen width. Lines on the screen are always printed with a width of 1. However, some turtles, when printed with a pen width of 1, do not look very good. Other turtles, because of their many overlapping lines, will look bad is the pen width is too thick.

For this reason, you are asked to specify the pen width you wish to use to print the turtle. A width of zero tells the printer to use the thinnest lines it is capable of printing. Larger widths cause thicker lines to be printed. On my HP DeskJet printer, I typically use widths between 0 and 4.

Please note that what you see on a printer can seem completely different than what you saw on the screen. There are many reasons for this. The biggest reason is simply that line widths will vary, total number of pixels for drawing increases dramatically on the printer, and because colors on the monitor do not always match the printed colors well.

Saving Turtles

You may save turtles to a file. Currently, only the text of the turtle's Logo program is saved. You can edit this text, and thus the turtle's algorithm, and load the turtle once again. This allows you to modify turtles as you see fit.

You save a turtle by selecting the turtle (using a left-click), then selecting the Save Turtle command from the File menu. This will display a Save As Dialog box. Enter the name of the file you want to save the turtle in, and click the Save button. The filename will have the extension ".txt" added to it, unless you put the suffix on yourself. You load saved turtles using the Doping technique. You select a turtle to replace and use the Load Turtle command from the File menu. Select the file you saved the turtle in and it will replace the one selected.

You can also save and load populations. This saves all of the turtles in a population into a single file. Populations can be saved to a file using the Save Population command in the File menu. Populations can be loaded again into a population window using the Load Population command in the File menu. When you load a saved population, only the number of turtles in the window you are loading into will be loaded. In other words, if a saved population file has 100 turtles in it, and you load it into a population window that is displaying 50 turtles, only the first 50 turtles will be loaded from the file.

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