Something is wrong with programming syntax

I never understood all this interest in DSL (domain specific languages). I’ve seen beautiful code done in a DSL-way (whatever it means) in all kind of languges from C to Lisp for ages.

I suppose the emergence of Ruby and the renewed interest in Smalltalk and lisp-based languages like Clojure made DSL an interesting topic for blog posts.

But I must admit that maybe we need to explain what DSL means… or why a good API design is always needed, because:

// describe the optimization problem
LinearObjectiveFunction f = new LinearObjectiveFunction(new double[] {-2,1}, -5);
Collection constraints = new ArrayList();
constraints.add(new LinearConstraint(new double[] {1,2}, Relationship.LEQ, 6));
constraints.add(new LinearConstraint(new double[] {3,2}, Relationship.LEQ, 12));
constraints.add(new LinearConstraint(new double[] {0,1}, Relationship.GEQ, 0));

// create and run the solver
RealPointValuePair solution = new SimplexSolver().optimize(f, constraints, GoalType.MINIMIZE, false);

// get the solution
double x = solution.getPoint()[0];
double y = solution.getPoint()[1];
double min = solution.getValue();

…is not a good API Ben.

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Published:: 07.08.09 / 10am

Category:: programming

rogersm 07.08.09 / 10pm

A friend recomends Fowler’s upcoming book about DSL

Ben McCann 08.10.09 / 6am

I’d be interested to hear what you think should be improved in the API or what you perceive the shortcomings to be. Also, if you want a different interface to the solver you can run it via Google Spreadsheets.

rogersm 08.10.09 / 9am

If the text representation of the LP is better than the Java one, why not use the text description of the problem as input?

I suspect you want to use the compiler type checking functionality to check for errors, but I don’t think it is acceptable to transform a perfectly working mathematical notation:

 x + 2y < = 6

new double[] { 1, 2 }, Relationship.LEQ, 6

just to use the compiler to check for errors.

Also, why this double[] casting? Is the L.P. able to work in the integer domain?

Addittionally using a getter named getPoint

solution.getPoint()[0]

to return an array of points does not seem to make a lot of sense to me.

My Java knowledge is minimal, and I suspect the language does not encourage to leave the set values, compute, get results way of thinking but the API is horrible.

The original text description is written in 53 characters and is easier to understand than the 478 lines used in the Java code.

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Something is wrong with programming syntax

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