Evaluator

Provides interfaces and implementations for logic constructs that return values without accepting arguments, either via closure captures, global state, calculation or otherwise.

Usage

Evaluator types

The three main evaluator types are ImmEval, Eval and RcEval (there's also DummyEval, which is rarely useful except for dynamically dispatched evaluator calls).

ImmEval

Evaluates Sized values using a closure without any caching.

Eval

Evaluates Copy-able values using an internal cache.

RcEval

Evaluates all kinds of values by returning a reference counter to the result. The most flexible yet the slowest type.

DummyEval

Takes a single Clone-able (remember, Copy implies Clone) object and returns it when evaluated. Useful if you have a Box<dyn Evaluator> and want to save a few cycles on the closure indirection if the evaluator which you placed there always returns the same value.

You can implement your own evaluators by implementing the Evaluator and RcEvaluator traits, which are responsible for the eval() methods.

Creating evaluators

Evaluators are created using the From trait, taking a closure as the only argument. They accept closures (or any type that implements Fn, really) that returns the kind of value that the evaluator accepts as the output (Sized for ImmEval, Copy for Eval and any value for RcEval).