A rule of thumb for implementing a "Low Coupling Principle" for objects
[http://www.ccs.neu.edu/research/demeter/demeter-method/LawOfDemeter/object-formulation.html]
[http://www.ccs.neu.edu/research/demeter/demeter-method/LawOfDemeter/general-formulation.html].

"The Law of Demeter was originally formulated as a style rule for designing object-oriented systems. "Only talk to your immediate friends" is the motto. The style rule was discovered at Northeastern University in the fall of 1987 by Ian Holland. 

A more general formulation of the Law of Demeter is: '''Each unit should have only limited knowledge about other units: only units "closely" related to the current unit.''' Or: Each unit should only talk to its friends; Don't talk to strangers."

''What has this got to do with tcl?''

Consider '''lset''' or some of the extra features proposed for various new or enhanced commands,
for example recent TIPs[http://www.tcl.tk/cgi-bin/tct/tip/] TIP 111 and TIP 127.

By allowing access to the extra depth into nested lists or dictionaries, coupling is increased.

It's a trade off between increased coupling between the code and the data and increased
performance.

Increased coupling makes code more fragile or more resistant to change.

This not to say that tcl should not allow such deep indexing, but people should be
clear on the consequences.

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''Created by [escargo] on 28 Feb 2003''