CSC151.02 2003F, Class 26: Local Procedure Bindings

Admin
* Did anyone go to the McGlotten talk?
* New reading
* Questions on yesterday's lab?
* Behave at the 10/10 party, which is further evidence that Grinnell students cannot count.
* Food

Overview:
* Review: What is a local variable?
* Why have "local" procedures.
* Technique one: letrec
* Technique two: Named let
* Lab

Why do we want local variables and local procedures?
* Local variables can clarify your code.  Makes it clearer what you're talking about in a long expression if you name that expression.
* Simplifies the husk-and-kernel programming strategy in that the husk really protects the kernel; no one can call the kernel directly.
* Simplifies the creation of helper procedures.
* Sam doesn't require as much documentation for local procedures.  A summary of the purpose is still nice.
* Makes it easier to name things (or at least shorter names), e.g., kernel rather than kernel-of-longest-thing-in-list-helper.

A Problem!  let and let* don't let you write recursive local procedures