Small errata in Ch. 12 and 13

[Ben]

A couple more errata, from Chapters 12 and 13.

1) pg 258, Figure 12.8a. In the line drawings, the slopes are written as dy/dx and a/b. The dy/dx is correct, but the other one should be b/a, not a/b (assuming it's written as y/x, but otherwise the dy/dx should be dx/dy).

2) pg 270. Keyboard.readString is actually Keyboard.readLine in the API.

3) pg 277, 2nd to last line: expect should be except.

[Mike In Chicago]

Also, on page 276, under the section marked "Complete Test", it states:

"... using the Pong game, whose source code is available in projects/12/Pong"

At least in the most recent software download, it is not there.  It can be found in projects/11/Pong