.. index:: single: validated .. _validated/0:

.. rst-class:: right

object

validated

Types and predicates for type-checking and handling lists of validation terms. Inspired by Scala Cats and Kotlin Arrow.

| Availability: | logtalk_load(validations(loader))

| Author: Paulo Moura | Version: 1:0:0 | Date: 2026-02-22

| Compilation flags: | static, context_switching_calls

| Provides: | :ref:`type::type/1 <type/0::type/1>` | :ref:`type::check/2 <type/0::check/2>` | :ref:`arbitrary::arbitrary/1 <arbitrary/0::arbitrary/1>` | :ref:`arbitrary::arbitrary/2 <arbitrary/0::arbitrary/2>` | :ref:`arbitrary::shrinker/1 <arbitrary/0::shrinker/1>` | :ref:`arbitrary::shrink/3 <arbitrary/0::shrink/3>` | :ref:`arbitrary::edge_case/2 <arbitrary/0::edge_case/2>` | Uses: | :ref:`list <list/0>` | :ref:`random <random/0>` | :ref:`type <type/0>`

| Remarks:

• Type-checking support: Defines a validated(ValueType, ErrorType) type for checking validation terms where the value and error terms must be of the given types.
• QuickCheck support: Defines clauses for the type::arbitrary/1-2, arbitrary::shrinker/1, arbitrary::shrink/3, and arbitrary::edge_case/2 predicates to allow generating random values for the validated(ValueType, ErrorType) type.

| Inherited public predicates: | (none)

.. contents:: :local: :backlinks: top

Public predicates

.. index:: valids/2 .. _validated/0::valids/2:

valids/2 ^^^^^^^^^^^^

Returns the values stored in validation terms that hold valid values.

| Compilation flags: | static

| Template: | valids(Validations,Values) | Mode and number of proofs: | valids(+list(validation),-list) - one

---

.. index:: invalids/2 .. _validated/0::invalids/2:

invalids/2 ^^^^^^^^^^^^^^

Returns a flattened list with all errors stored in invalid validation terms.

| Compilation flags: | static

| Template: | invalids(Validations,Errors) | Mode and number of proofs: | invalids(+list(validation),-list) - one

---

.. index:: partition/3 .. _validated/0::partition/3:

partition/3 ^^^^^^^^^^^^^^^

Retrieves and partitions valid values and flattened accumulated errors from validation terms.

| Compilation flags: | static

| Template: | partition(Validations,Values,Errors) | Mode and number of proofs: | partition(+list(validation),-list,-list) - one

---

.. index:: map/3 .. _validated/0::map/3:

map/3 ^^^^^^^^^

Applies a closure to each list element to generate validation terms and returns a pair Values-Errors accumulating all valid values and all errors in one pass.

| Compilation flags: | static

| Template: | map(Closure,Terms,ValuesErrors) | Meta-predicate template: | map(2,*,*) | Mode and number of proofs: | map(+callable,+list,--compound) - one

---

.. index:: map/4 .. _validated/0::map/4:

map/4 ^^^^^^^^^

Applies a closure to each list element to generate validation terms and returns valid values and accumulated errors in one pass.

| Compilation flags: | static

| Template: | map(Closure,Terms,Values,Errors) | Meta-predicate template: | map(2,*,*,*) | Mode and number of proofs: | map(+callable,+list,-list,-list) - one

---

.. index:: sequence/2 .. _validated/0::sequence/2:

sequence/2 ^^^^^^^^^^^^^^

Sequences a list of validation terms into a single validation term, accumulating all errors.

| Compilation flags: | static

| Template: | sequence(Validations,Validation) | Mode and number of proofs: | sequence(+list(validation),--nonvar) - one

---

.. index:: traverse/3 .. _validated/0::traverse/3:

traverse/3 ^^^^^^^^^^^^^^

Applies a closure to each list element to generate validation terms and then sequences them, accumulating all errors.

| Compilation flags: | static

| Template: | traverse(Closure,Terms,Validation) | Meta-predicate template: | traverse(2,*,*) | Mode and number of proofs: | traverse(+callable,+list,--nonvar) - one

---

Protected predicates

(no local declarations; see entity ancestors if any)

Private predicates

(no local declarations; see entity ancestors if any)

Operators

(none)

.. seealso::

:ref:`validation <validation/0>`, :ref:`validation(Validation) <validation/1>`, :ref:`type <type/0>`, :ref:`arbitrary <arbitrary/0>`