A nice Squeak tutorial.
it has been awhile since we mentioned Squeak, but there were days when it was mentioned quite regularly...
Ken Arnold, "programmer and author who helped create Jini, JavaSpaces, Curses, and Rogue", writes that the usefulness of generics is outweighed by their complexity. Ken is talking about Java 5, but such critiques are well-known for C++, and C# is not immune either. Ken describes the Java case as follows:
The article contains a few simple supporting examples, including the interesting definition of Java 5's
Enum<T extends Enum<T>>
...which "we're assured by the type theorists ... we should simply not think about too much, for which we are grateful."
If we accept the article's premise, here's a question with an LtU spin: do the more elegant, tractable polymorphic inferencing type systems, as found in functional languages, improve on this situation enough to be a viable alternative that could address these complexity problems? In other words, are these problems a selling point for better type systems, or another barrier to adoption?
[Thanks to Perry Metzger for the pointer.]
Method mixins - written by Erik Ernst
This paper provides an interesting perspective on the role of variables in programming. It is about a construct called method mixins, but the discussion about the role of variables in Sec. 2 is relatively independent of the specific construct proposed in the paper:
Metaclasses are a nifty (albeit somewhat arcane) OOP feature. I found the article interesting, but I had a lot of trouble with the elaborate type soundness proofs. Those who are unfamiliar with metaclass programming might want to read some introductory material before tackling this article. Metaclass Programming in Python by Mertz and Simionato is a particularly good overview.
Parameterized Unit Tests. Nikolai Tillmann; Wolfram Schulte; Wolfgang Grieskamp
Parameterized unit tests extend the current industry practice of using closed unit tests defined as parameterless methods. Parameterized unit tests separate two concerns: 1) They specify the external behavior of the involved methods for all possible test arguments. 2) Test cases can be re-obtained as traditional closed unit tests by instantiating the parameterized unit tests. Symbolic execution and constraint solving can be used to automatically choose a minimal set of inputs that exercise a parameterized unit test with respect to possible code paths of the implementation. In addition, parameterized unit tests can be used as symbolic summaries which allows symbolic execution to scale for arbitrary abstraction levels. We have developed a prototype tool which computes test cases from parameterized unit tests; it is integrated into the forthcoming Visual Studio Team System product. We report on its first use to test parts of the .NET base class library.
By adding parameters the authors turn a closed unit test into a universally quantified conditional axiom that must hold for all inputs under specified assumptions. Adding parameters improves the expressiveness of unit cases, at the expense of not providing concrete test cases. Symbolic execution is used to automatically find the set of parameters that have to be tested.
This seems like an interesting approach to unifying unit testing and algebraic specifications.
Metaphor is a strongly-typed, multi-stage, object-oriented programming language. Metaphor is based on a subset of C# and is extended with multi-stage programming constructs in the style of MetaML or MetaOCaml. Metaphor is implemented as a compiler on the .NET CLR.
A lot of language theory goes past here on Lambda the Ultimate, but we rarely see that theory directly impacting commercial programmers.
We discussed Hibernate, and O/R mapping in general, a couple of times so I thought this might be of interest.
An critique of OOP. The article is about OOP as a SE/design approach and doesn't directly attack the issue from a PL angle, but it might still interest LtU readers.
From a PL point of view, I would have chnaged the title to: OOP Is Much Better in Theory Than in Practice, (And the Theory Isn't too Good anyway).
Polyglot is a compiler front end framework for building Java language extensions that doesn't seem to have been mentioned here.
Amongst the extensions is an implementation of nested inheritance which, I admit, I don't completely get. There's a discussion (moderately critical) of the paper in the context of OCaml that starts here.
This caught my eye while scanning the latest Caml Weekly News - a useful summary of the (rather high volume) (O)Caml list.
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