panproto-expr

Expression AST and bounded evaluator used by migrations and schema enrichments.

Evaluation model

The language provides lambdas, application, lexical let bindings, pattern matching, records, lists, field access, and built-in operations. BuiltinOp has 60 variants covering arithmetic, comparison, strings, collections, records, conversion, hashing, and graph queries. Built-ins are first-class values and support partial application.

The base evaluator performs no I/O and mutation is confined to its evaluation state. Graph-query built-ins require an InstanceResolver; calling them through the base eval or apply_builtin path returns ExprError::NoInstanceContext.

Evaluation is bounded by EvalConfig. Its defaults are 100,000 steps, depth 256, and list length 10,000. Reaching a bound returns an error. These limits contain runaway evaluation; they do not prove termination below the configured bound.

Example

use panproto_expr::{Env, EvalConfig, Expr, Literal, eval};

let expr = Expr::app(
    Expr::lam("x", Expr::var("x")),
    Expr::Lit(Literal::Int(3)),
);
let value = eval(&expr, &Env::new(), &EvalConfig::default())?;

Public API

License

MIT