message

tuprolog.solve.exception.error.message

Message errors: the errors carrying an arbitrary thrown term, fitting no ISO error family.

When Prolog code throws a term that is not an ISO error(Type, Extra) one (e.g. throw(my_problem)), or a primitive needs to throw a custom term, 2P-Kt represents it as a MessageError, whose content is the thrown term. Catching it in Prolog unifies the catcher with that very term.

Build them with message_error.

Examples:

>>> from tuprolog.core import atom
>>> from tuprolog.solve.library import library
>>> from tuprolog.solve.primitive import primitive
>>> from tuprolog.solve.prolog import prolog_solver
>>> def complain(request):
...     raise message_error(atom("my_problem"), request.context)
>>> lib = library("demo", primitives={"complain/0": primitive(complain)})
>>> solver = prolog_solver(libraries=lib)
>>> solver.solve_once("catch(complain, E, true)")["E"]
my_problem

See Also

2P-Kt's documentation on errors and exceptions.

MessageError module-attribute

MessageError = _errors.MessageError

The error carrying an arbitrary thrown term, used when no other LogicError fits.

The JVM class (also a tuprolog.errors.PrologMessageError). Members (snake_case aliases as well): content, the thrown term; besides those of tuprolog.solve.exception.LogicError.

message_error

message_error(
    content: Term,
    context: ExecutionContext,
    cause: Any = None,
) -> MessageError

Creates the error throwing an arbitrary term.

Parameters:

Name	Type	Description	Default
content	Term	the term to throw; Prolog's catch/3 unifies its catcher with it.	required
context	ExecutionContext	the execution context in which the error occurs (e.g. a request's context).	required
cause	Any	the exception causing this one, if any.	None

Returns:

Type	Description
MessageError	The error.

Note

Calls 2P-Kt's MessageError.Companion.of, which (not being static on the JVM) is not reachable as MessageError.of.

Examples:

>>> from tuprolog.solve import signature
>>> from tuprolog.solve.exception.error import *
>>> from tuprolog.solve.prolog import prolog_solver
>>> context = prolog_solver().current_context
>>> from tuprolog.core import atom
>>> message_error(atom("hello"), context).content
hello