LARA

Lecture 06a: Simple Semantic Analysis

Scopes of Symbols

Simple Errors beyond Syntax

Identifiers vs Symbols Example

Simple Language with Local Variables

Scoping Rules Affect Program Meaning

Notation for Maps

Maintaining Maps

Implementation: Symbol Tables and Error Reporting

Symbol Table Contents

Functional versus Imperative Maps

An Efficient Imperative Map

Functional Maps

Efficient Comparison for Identifiers

Reporting Errors Based on Syntax Tree

Type Checking Rules for a Simple Language

Type Rules: local rules that say how types should agree on each syntax tree node. Can be used to derive type checking algorithms:

  • bottom-up: constants have types, variables have types (from declarations), so propagate through operators
  • top-down: resulting expressions have types, deduce the types of argument operators
  • combination

Rules are declarative specifications, they do not directly say in which direction to propagate

References