|The alpha rewrite rule|
An alpha conversion changes the names of lambda expression formal parameters
An example of an alpha rewriting. The name a replaces x and the name b replaces y.
Examples of an illegal alpha conversion. f is a free name in the lambda expression. A free name is used, but not defined (bound) in the lambda expression. In case we rename one of the parameters to f, the free name will be bound, hereby causing an erroneous name binding.