Show HN: Program Synthesis for Ruby (opens in new tab)

> But doesn't this just mean that instead of writing your code and logic in Ruby you're writing it in RDL?

RDL allows the specification of types and effect labels only. You still write the tests in standard Ruby and synthesized code should satisfy the logic as checked by the tests.

> Also, it would be great to see some examples in the README or in an examples folder. It's kind of hard for me to tell exactly what I need to write and what to call to generate the Ruby.

Sorry for the sparse documentation, I plan to improve that. I have added an example to the readme. Other examples can be found in `test/benchmark` folder.

> But doesn't this just mean that instead of writing your code and logic in Ruby you're writing it in RDL?

..and write a test for it..? :|

Indeed, there is rich prior work on example based program synthesis. Often these use inductive logic programming or aided by SMT solvers if these examples can be lifted to solver level values (think integers or booleans, or data types made from those).

However, not all program values can be easily lifted to solvers. So the goal with RbSyn is to allow the programmer to write the same tests they would have written anyway to check their program correctness, without any extra fiddling. As tests subsume examples, we expect more program behavior can be specified than just using simple examples.

> I do wonder if the benefit will really be significant enough to make it worth it.

I have often pondered on what makes a program synthesis tool useful. I expect writing code as art as much as it is science, and people like to express code in the way they model system behavior in their head. In that regard, I do not think program synthesis tools will enable you to automate away large parts of code, but I do think it will automate mundane parts of a program; like writing utility methods, or filling in a partial program when enough information can be gathered from surrounding context (such as the arguments you write for a substring function).

That is a fair concern. The tool only guarantees correctness up to the level checked by the tests you provide. So if all corner cases are not covered, RbSyn will generate some program that passes the tests, but might not pass unspecified corner cases. I suspect the missing cases will be clear with a manual audit of the synthesized code, and you can add update the synthesized code manually or add requisite tests.