PoPL Lecture 10

• Till now, we studied syntax
• Now, semantics or dynamics/evaluations of expressions
• Again, defining syntax formally in terms of trees

Overview of what we will cover:

• Addition language
• Syntax and interactive semantics

Syntax:

• Consider the syntax for the addition language

  

• Hereon, “term” = inductive term unless otherwise specified
• How to evaluate: say 2() + (3() + 4()) → 2() + 7() → 9()

• Defining a transition system:

  

• Defining something? TODO

  

  Along those lines, what is a Run

  

• Term graph as a system

  

  Useful for lots of things, including data structures, can look at what as
  transitions and navigate around.

• TODO Subterms, replacements

• Addition and rewrite rules

  

• TODO this well. Addition as a system