[plt-scheme] Programming and Martial Arts

I've been trying out a different metaphor as a way of making students
stick to the Design Recipe:

In martial arts, the first thing you learn is to do simple motions
very precisely.  Ditto for ballet, where the first thing you learn is
the five positions.

Once those are committed to muscle memory, you can go on to
combinations and variations.

Same deal for programming via HtDP: first practice using the templates
until you can do it without thinking.  Then you can go on to
combinations and variations.

And muscle memory is absolutely critical: that's knowledge that
compiled in your head, not interpreted.

--Mitch