object

expected

Constructors for expected terms. An expected term contains either a value or an error. Expected terms should be regarded as opaque terms and always used with the expected/1 object by passing the expected term as a parameter.

Availability:
logtalk_load(expecteds(loader))
Author: Paulo Moura
Version: 2:2:0
Date: 2026-02-21
Compilation flags:
static, context_switching_calls
Provides:
type::type/1
type::check/2
Remarks:

  • Type-checking support: This object also defines a type expected for use with the type library object.

Inherited public predicates:
(none)

Public predicates

of_unexpected/2

Constructs an expected term from an error that represent that the expected value is missing.

Compilation flags:
static
Template:
of_unexpected(Error,Expected)
Mode and number of proofs:
of_unexpected(@term,--nonvar) - one

of_expected/2

Constructs an expected term from an expected value.

Compilation flags:
static
Template:
of_expected(Value,Expected)
Mode and number of proofs:
of_expected(@term,--nonvar) - one

from_goal/4

Constructs an expected term holding a value bound by calling the given goal. Otherwise returns an expected term with the unexpected goal error or failure represented by the Error argument.

Compilation flags:
static
Template:
from_goal(Goal,Value,Error,Expected)
Meta-predicate template:
from_goal(0,*,*,*)
Mode and number of proofs:
from_goal(+callable,--term,@term,--nonvar) - one

from_goal/3

Constructs an expected term holding a value bound by calling the given goal. Otherwise returns an expected term with the unexpected goal error or the atom fail representing the unexpected failure.

Compilation flags:
static
Template:
from_goal(Goal,Value,Expected)
Meta-predicate template:
from_goal(0,*,*)
Mode and number of proofs:
from_goal(+callable,--term,--nonvar) - one

from_goal/2

Constructs an expected term holding a value bound by calling the given closure. Otherwise returns an expected term holding the unexpected closure error or the atom fail representing the unexpected failure.

Compilation flags:
static
Template:
from_goal(Closure,Expected)
Meta-predicate template:
from_goal(1,*)
Mode and number of proofs:
from_goal(+callable,--nonvar) - one

from_generator/4

Constructs expected terms with the values generated by calling the given goal. On goal error or failure, returns an expected term with the unexpected goal error or failure represented by the Error argument.

Compilation flags:
static
Template:
from_generator(Goal,Value,Error,Expected)
Meta-predicate template:
from_generator(0,*,*,*)
Mode and number of proofs:
from_generator(+callable,--term,@term,--nonvar) - one_or_more

from_generator/3

Constructs expected terms with the values generated by calling the given goal. On goal error or failure, returns an expected term with, respectively, the unexpected goal error or the atom fail representing the unexpected goal failure.

Compilation flags:
static
Template:
from_generator(Goal,Value,Expected)
Meta-predicate template:
from_generator(0,*,*)
Mode and number of proofs:
from_generator(+callable,--term,--nonvar) - one_or_more

from_generator/2

Constructs expected terms with the values generated by calling the given closure. On closure error or failure, returns an expected term with, respectively, the unexpected closure error or the atom fail representing the unexpected closure failure.

Compilation flags:
static
Template:
from_generator(Closure,Expected)
Meta-predicate template:
from_generator(1,*)
Mode and number of proofs:
from_generator(+callable,--nonvar) - one_or_more

from_optional/3

Converts an optional term to an expected term. Returns an expected term holding the value if the optional term is not empty. Returns an expected term with the given error otherwise.

Compilation flags:
static
Template:
from_optional(Optional,Error,Expected)
Mode and number of proofs:
from_optional(+nonvar,@term,--nonvar) - one

Protected predicates

(no local declarations; see entity ancestors if any)

Private predicates

(no local declarations; see entity ancestors if any)

Operators

(none)

See also

expected(Expected), type