The K framework: http://www.kframework.org/index.php/Main_Page http://www.kframework.org/index.php/Main_Page It's a system for formally expressing the semantics

The K framework: http://www.kframework.org/index.php/Main_Page http://www.kframework.org/index.php/Main_Page It's a system for formally expressing the semantics of programming languages and getting an interpreter. That said, the parent's claim about CHR is rather broad, and you may have read too much into it. It's a library for writing new constraint programming libraries for Prolog. Combined with operator overloading, you get embedded DSLs for constraint systems. That's great, and it is "language development" in some sense. But CHR is not a tool for implementing interpreters or compilers for new programming languages (though it may be useful for some subtasks).