Chapter 10. The Form API, Page 244

Location on the page: 
Final blockof code, beginning function formexample_nameform(
Chapter: 
10. The Form API
Error: 

The signature of the called function is incorrect. This is also incorrect throughout the downloadable code for this chapter.

Correction: 

The correct signature is
function formexample_nameform($form_state=NULL)

$form_state is passed in the first parameter.

Description of the Error: 

$form_state is passed in the first parameter, not the second.