object

validation

Constructors for validation terms. A validation term is either valid(Value) or invalid(Errors) where Errors is a list of errors. Validation terms allow applicative-style error accumulation.

Availability:
logtalk_load(validations(loader))
Author: Paulo Moura
Version: 1:0:0
Date: 2026-02-22
Compilation flags:
static, context_switching_calls
Provides:
type::type/1
type::check/2
Uses:
list
type
Remarks:

  • Type-checking support: Defines a validation type for use with the type library object.

Inherited public predicates:
(none)

Public predicates

of_valid/2

Constructs a validation term holding a valid value.

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

of_invalid/2

Constructs a validation term holding a single error.

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

of_invalids/2

Constructs a validation term holding a list of errors.

Compilation flags:
static
Template:
of_invalids(Errors,Validation)
Mode and number of proofs:
of_invalids(@list,--nonvar) - one

from_goal/4

Constructs a validation term holding a value bound by calling the given goal. Otherwise returns a validation term with a single error represented by the Error argument.

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

from_goal/3

Constructs a validation term holding a value bound by calling the given goal. Otherwise returns a validation term with a single error being the goal error or the atom fail representing goal failure.

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

from_goal/2

Constructs a validation term holding a value bound by calling the given closure. Otherwise returns a validation term with a single error being the closure error or the atom fail representing closure failure.

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

from_generator/4

Constructs validation terms with the values generated by calling the given goal. On goal error or failure, returns a validation term with a single error represented by the Error argument.

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

from_generator/3

Constructs validation terms with the values generated by calling the given goal. On goal error or failure, returns a validation term with, respectively, a single error being the goal error or the atom fail representing goal failure.

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

from_generator/2

Constructs validation terms with the values generated by calling the given closure. On closure error or failure, returns a validation term with, respectively, a single error being the closure error or the atom fail representing closure failure.

Compilation flags:
static
Template:
from_generator(Closure,Validation)
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 a validation term. Returns a valid term holding the value if the optional term is not empty. Returns an invalid term with the given error otherwise.

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

from_expected/2

Converts an expected term to a validation term. Returns a valid term holding the value if the expected term holds a value. Returns an invalid term with the expected term error otherwise.

Compilation flags:
static
Template:
from_expected(Expected,Validation)
Mode and number of proofs:
from_expected(+nonvar,--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

validation(Validation), validated, type, arbitrary