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Unformatted text preview: anel In this section we explain how to create, edit and save worlds.
Worlds can be edited using a variety of diﬀerent commands. Each
of these can be undone using the Undo command from the File
menu, and redone using the Redo command, on the same menu. 3.2.1 Adding blocks To put a block on the grid, simply click the New button on the
tool bar. This is the leftmost button on the toolbar, and looks like
an arrow pointing at the world, with blocks above it. Try this out.
The size and shape of block that is created can be controlled by
setting a preference (see section 3.6). A small cube is created by
default. 3.2.2 Selecting blocks A block can be selected by clicking on it. The block will change
color to indicate its selection. To deselect a block, click elsewhere
in the world window.
To select more than one block, hold down the command key
(control key on Windows) while clicking on the blocks. If many
blocks are selected, and you want to deselect one of them, click on
it while holding down the shift key. 3.2.3 Moving blocks To move a block, position the cursor over the block and drag it to
the desired position. (That is, move the mouse’s arrow over the
block and then, with the button depressed, move the mouse until
the block is where you want it.) If multiple blocks are selected, they
will all move. There is one exception to this. Large blocks are so
big that they overlap onto the adjoining squares. Consequently, it
is impossible to move blocks so that a large block adjoins a square
that is occupied. Using Tarski’s World / 19 If you move a block (or blocks) too close to the edge it will fall
oﬀ. 3.2.4 Sizing and shaping blocks To change a block’s shape, select it and click on one of the shape
buttons on the toolbar. These display a tetrahedron, cube and dodecahedron and change the shape appropriately. If multiple blocks
are selected all will changed to the new shape.
Similarly, to change a block’s size, select it and click on one
of the size buttons on the toolbar. These display circles of small,
medium and large sizes. If multiple blocks are selected all will
changed to the new size. There is one exception to this. Large
blocks are so big that they overlap onto the adjoining squares.
Consequently, it is impossible to make a block large if it adjoins
any square which has a block on it. 3.2.5 Naming blocks When a block is selected, the name checkboxes on the toolbar
are activated. To add a name to the selected block, click on the
appropriate name button, which looks like a cube with a name on
it. If the box is already selected, the name will be removed from
In ﬁrst-order logic, one object can have several names, but two
objects cannot share the same name. Hence Tarski’s World lets
you give a block more than one name, but once a name is used,
that name cannot be assigned to another block. So if one block
is named a and you want a diﬀerent block to be named a, you
must remove the name from the ﬁrst block before adding it to the
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This document was uploaded on 01/26/2014.
- Winter '14