Lambda the Ultimate

Dyna is a language I stumbled upon by accident today. What I find interesting qualities of it are its claimed clean compilation to C++ and its non-standard semantics.

Dyna is a small, very-high-level programming language that makes it easy to specify dynamic programs and train their weights. You write a short declarative specification in Dyna, and the Dyna optimizing compiler produces efficient C++ classes that form the core of your C++ application.

Natural applications in NLP include various kinds of parsing, machine translation, speech decoding, and finite-state modeling. Dyna also has many other applications, especially in other applied AI areas, since dynamic programming (and its degenerate case, tree search) is a common strategy for solving combinatorial optimization problems.

Properly speaking, Dyna is a "weighted" logic programming language: terms have values, and Horn clauses are replaced by aggregation equations. It is Turing-complete. You can also think of Dyna as extending compiled C++ with powerful deductive database features.