solve/it.unibo.tuprolog.solve.function/AbstractEvaluator

AbstractEvaluator

abstract class AbstractEvaluator<E : ExecutionContext, T : Term>(request: Solve.Request<E>, index: Int?) : TermVisitor<T>

Base TermVisitor for reducing an expression Term to a value of type T, recursively resolving any Struct sub-term whose Signature matches a LogicFunction loaded in request's it.unibo.tuprolog.solve.library.Runtime (loadedFunctions) into that function's Compute.Response.result. A Struct matching no loaded function is handled by unevaluable (by default, an error).

Subclasses customize the exact evaluation semantics via staticCheck (run once per visited term, before recursing into sub-terms) and dynamicCheck (run on each sub-term's already-evaluated result); see ArithmeticEvaluator for a concrete example enforcing ISO arithmetic-expression validity.

Parameters

request

the request of the primitive in which the evaluation should happen

index

the index of the argument being evaluated in the aforementioned primitive

Inheritors

ArithmeticEvaluator

ExpressionEvaluator

ExpressionReducer

Constructors

AbstractEvaluator

constructor(request: Solve.Request<E>, index: Int?)

Functions

defaultValue

open override fun defaultValue(term: Term): T

unevaluable

open fun unevaluable(struct: Struct): Term

Called when struct matches no LogicFunction in loadedFunctions; by default raises a TypeError (TypeError.Expected.EVALUABLE). Overridden by ExpressionReducer to leave non-evaluable sub-terms untouched instead of failing.