In a message dated Fri, 25 Aug 2006, Juerd writes:

Trey Harris skribis 2006-08-25 11:33 (-0700):
Ok... same thing from a DBC perspective.  Subclasses can add functionality
(by AND'ing postconditions), or remove constraints (by OR'ing
preconditions), but they can't traditionally remove functionality or add
constraints.  I just want to read about how that works.

The keyword is "traditionally". We're used to a dynamic language that
bends the rules all the time, including runtime. Why would Perl stick to
academic limitations, while optimizing for the most common use is the

   my Array::Const @foo;
   @foo ~~ Array;  # False?! Please, no.

Though in practice I expect "is ro" to be used, not a subtype or subset.

Explain to me how "nontraditional" DBC might work in an internally consistent way. Otherwise, this is hand-waving. :-)


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