15-851 Computation and Deduction
Lecture 2: Natural Semantics
We define the operational semantics of Mini-ML by a set of inference
rules that allow us to establish the relation between an expression and
its value. This style of definition we follow is called natural semantics.
We then use this definition to establish our first meta-theorem, namely
that the result of evaluation (if it exists) is in fact a value. The
techniques we use will be with us for the rest of the course, namely
structural induction and inversion.
We also define the typing rules for Mini-ML that sort out valid from
invalid expressions in preparation for the type preservation theorem
in the next lecture.