Recently there was a thread on this forum that touched on
preconditions of creation procedures. It reminded me of a time
several years ago when I believed I had found a hole in Eiffel's
otherwise elegant design. I came upon a case (which I had foolishly
written myself) where a precondition of a creation procedure could
not be called by a client attempting to instantiate the class,
because the precondition was a feature of the class itself (a
creation procedure Catch-22). Something like this:
class
A
create
make
feature -- Initialization
make is
require
f
do
end
feature
f: BOOLEAN is
do
Result := False;
end
end
Wondering if the ECMA standard had anything to say about this case, I
checked the standardization document, and found section 8.20.3, which
declares that a creation procedure like 'make' should be invalid
(validity check VGCP), because there is an unqualified call in the
precondition.
This class, though, compiles cleanly in EiffelStudio 6.2 (and
predictably throws a run-time error if you try to instantiate A).
I'm wondering, is this an example of a compiler check that
EiffelStudio will one day include? The ink is hardly dry on the ECMA
standard; it's understandable that not all its rules would be in the
current version of the compiler. Is implementing all of the ECMA
standard the eventual goal of EiffelStudio?
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