| I guess one thing that bothers me a little is that people are quick to say that Eiffel is "elegant" without really looking at it. I fear that such statements will become self-fulfilling prophecies, with those programmers interested in elegance migrating over to Eiffel rather than sticking with Ada.
In particular, although I like the assertion stuff in Eiffel, I think the language has a number of "inelegant" aspects. For example:
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exception handlers only at the top level of a routine, with the only way to "handle" an exception being by retrying the whole routine.
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No way to return from a routine in the middle. This makes it a pain in the neck to search through a list for something in a loop, and then return immediately when you find what you want. (I have never found the addition of extra boolean control variable a help to the understanding of an algorithm.)
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Namespace control handled by a separate sublanguage, and no real higher level concept of "module" or "subsystem."
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An obscure notation like "!!" being used for an important and frequent operation (construction).
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No way to conveniently "use" another abstraction without inheriting from it.
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No strong distinctions between integer types used for array indexing.
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Using the same operator ":=" for both (aliasing) pointer assignment, and for value assignment, depending on whether the type is "expanded." (Simula's solution was far preferable, IMHO).
And most critically:
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No separate interface for an abstraction. You can view a interface by running a tool, but this misses completely the importance of having a physical module that represents the interface, and acts as a contract between the specifier or user of an abstraction and its implementor. In Eiffel, one might not even be truly aware when one is changing the interface to an abstraction, because there is no particular physical separation between interface and implementation.
I consider many of the above problems quite serious, with some of them being real throwbacks to the old style of programming languages where there were no well defined interfaces or modules.
Hence, I cringe a bit when people say that Eiffel is the "most elegant" OOP and that they would use it if only it were practical to do so. In many ways, I think Ada is much better human-engineered than Eiffel, with important things like range constraints built into the language in a way that makes them convenient to use. Although general assertions are nice, they don't give you the kind of line-by-line consistency checks that Ada can give you.
To summarize --
Although Eiffel certainly has a number of nice features, I don't consider it ready for prime time as far as building and maintaining large systems with large numbers of programmers. And from a human engineering point of view, I think Ada is significantly better.
(Tucker Taft) |
