Andy and John: (if possible) automatically turn expressions with array
sub-expressions into iteration over the array(s)

Andy: Add routines to allow access to guide components.

Andy: Make keywords cycle, tension, etc. usable by three.asy.

Andy: Look at Java syntactic sugar for iterating over arrays.

Andy: Add void operator init() "constructor" for structures.

Andy: Suppress writing of assignment expression statements at interactive
prompt.
