expr-lang/expr

Health v2 · maintenance only

Adoption not part of the score

7989 stars · 527 forks observed · 2026-08-28

What it is AI-extracted, prompt v1, taxonomy v1, 2026-08-29, confidence not recorded

Expr is a Go-centric expression language and evaluation engine that compiles expressions into bytecode and runs them on a fast, safe virtual machine. It offers static type checking against Go environments, memory-safe and side-effect-free execution, and built-in functions for collections, making it ideal for dynamic configuration and business rules.

Use cases

• evaluate user-supplied expressions safely in a Go app
• build a rule engine for access control policies
• add dynamic configuration logic to a Go service
• type-check expressions against Go structs at compile time
• filter and map over collections with a small DSL
• let users write business rules without redeploying code

When to choose

• you need safe, terminating, side-effect-free expression evaluation in Go
• you want static typing and friendly compile-time errors for user-written expressions
• you need high-performance evaluation with a bytecode VM and reusable compiled programs
• you want seamless use of existing Go structs, maps, and methods as the expression environment

When to avoid

• you need a full general-purpose scripting language with loops and side effects
• your project is not in Go
• you need sandboxed execution of arbitrary user code beyond pure expressions

Facets

library · maturity stable

interpreter compiler configuration-management developer-tools programming-languages developer-tools backend go cross-platform expression-language rule-engine bytecode-vm static-typing safe-evaluation dsl automation

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