A very interesting note about ”variables.” One normally thinks of a variable as a data item, a name, a number, etc.  As discussed above PSL takes that a step higher.  But there is more.  In many places where one might think of placing a single value, PSL users can supply a list.  An interesting example of this is where colors are involved.  If the user supplies a list of colors PSL will shade the item by the colors in the list.  Furthermore, in the case of colors, one can intersperse other factors such as the orientation and spacing between the colors, and whether is is linear or radial.


 This is linear spacing.  This is radiant spacing - place "r" at the front of the list

A list of colors presented to the function that prints rows, such as in a statement, will cause the rows to cycle through the list of colors, one color per row.  Please see “Wizard” in PSL help.

Here’s another interesting example.

  One might not think of for use of variables is “geometric control” of images or graphics.  Scaling (anisotropic), location of the origin, and skewing can be controlled by variables. 


   For example the skew function accepts variables describing rotations about the x and y axis of graphics and text.  The same is true for much more mundane matters such as line thickness and color, dash patterns, and even “free form” line drawings.