Expr is a high-performance expression evaluation engine and language for Go applications. It functions as a dynamic rule engine that parses and executes custom logic and data validations at runtime without requiring the application to be recompiled.
The system utilizes a sandboxed logic executor to run expressions without side effects. It ensures program termination by employing instruction-level loop detection to prevent infinite loops and isolates the evaluation process from the host system.
The engine employs a bytecode-based virtual machine and abstract syntax tree analysis to achieve execution. It includes static type resolution and runtime type validation to ensure data correctness, using reflection to map external object properties to expression identifiers.