Constraint Handling Rules

Constraint Handling Rules (CHR) are a way to programmatically specify how to solve problems by defining rules that manage constraints—conditions or requirements. Think of constraints as rules or restrictions in a puzzle, and CHR as a system that automatically applies these rules to find solutions. When certain constraints are present, CHR rules trigger actions to simplify, combine, or eliminate constraints until a consistent solution emerges. It's widely used in areas like scheduling, decision-making, and type inference, providing a flexible and logical framework for managing complex relationships between different conditions.