Part 4: Defining IMP++

IMP++ extends IMP, which was discussed in Part 2 of this tutorial, with several new syntactic constructs. Also, some existing syntax is generalized, which requires non-modular changes of the existing IMP semantics. For example, global variable declarations become local declarations and can occur anywhere a statement can occur. In this tutorial we will learn the following:

• That (and how) existing syntax/semantics may change as a language evolves.
• How to refine configurations as a language evolves.
• How to define and use fresh elements of desired sorts.
• How to tag syntactic constructs and rules, and how to use such tags with the superheat/supercool options of kompile.
• How the search option of krun works.
• How to stream cells holding semantic lists to the standard input/output, and thus obtain interactive interpreters for the defined languages.
• How to delete, save and restore cell contents.
• How to add/delete cells dynamically.
• More details on how the configuration abstraction mechanism works.

Like in the previous tutorials, this folder contains several lessons, each adding new features to IMP++. Do them in order and make sure you completed and understood the previous tutorials.