15-317 Constructive Logic
Lecture 19: Metainterpreters

In this lecture we describe two interpreters for a Prolog-like fragment of logic in a Prolog-like metalanguage. Actually, we are slightly more abstract, but the specifications of the operational semantics of Horn logic can easily be transcribed into Prolog. In the first step, we use backtracking in the metalanguage to model backtracking in the object language. In a second, slightly lower-level interpreter we make this explicit, arriving at a form of abstract machine.

• Reading: lp:04-opsem.pdf (code), lp:05-backtrack.pdf (code)
• Previous lecture: Cut Elimination
• Next lecture: Saturation
• Key concepts:
  • Definitional interpreters
  • Soundness and nondeterministic completeness
  • Explicating choice
  • Explicit disjunction form

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Frank Pfenning