question about implicit differentiaion

Hello,
  I have been playing with implicit differentiation, and have noticed 
some strange behavior.

Consider the two files: implicit_1.mac, implicit_2.mac attached. Th

They simply give 2d and 3d examples of the use of the function 
'implicit_derivative'

They each can be loaded and work in separate maxima sessions.

When I try to put them in a single file, the scripts crash.   Check 
out   implicit_1a.mac

Any idea what is going on?


TIA,
 -sen


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