> ## Documentation Index
> Fetch the complete documentation index at: https://cantonfoundation-generated-reference-full-stack-preview.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# DA.Validation

> Reference documentation for Daml module DA.Validation.

<div class="x2mdx-ref-page x2mdx-ref-page--collection" />

<span id="module-da-validation-69700" />

<div class="x2mdx-ref-hero">
  <p class="x2mdx-ref-eyebrow">Daml module</p>

  <h1 class="x2mdx-ref-title">DA.Validation</h1>

  <p class="x2mdx-ref-summary">Validation type and associated functions.</p>

  <div class="x2mdx-ref-badges">
    <span class="x2mdx-ref-badge x2mdx-ref-badge--protocol">Daml</span>

    <a class="x2mdx-ref-badge x2mdx-ref-badge--added" href="#history-added-3-4-9">Added 3.4.9</a>

    <a class="x2mdx-ref-badge x2mdx-ref-badge--changed" href="#history-updated-3-5-1">Updated 3.5.1</a>
  </div>

  <dl class="x2mdx-ref-meta-grid">
    <div class="x2mdx-ref-meta-item">
      <dt>Module</dt>
      <dd>DA.Validation</dd>
    </div>

    <div class="x2mdx-ref-meta-item">
      <dt>Latest release</dt>
      <dd>3.5.7</dd>
    </div>
  </dl>
</div>

## Data Types

<span id="type-da-validation-types-validation-39644" />

### `data Validation err a`

A `Validation` represents eithor a non-empty list of errors, or a successful value.
This generalizes `Either` to allow more than one error to be collected.

Constructors:

<span id="constr-da-validation-types-errors-73825" />

* `Errors (NonEmpty err)`

<span id="constr-da-validation-types-success-12286" />

* `Success a`

Instances:

* instance [`Foldable`](/appdev/reference/daml-standard-library/da-foldable#class-da-foldable-foldable-25994) ([`Validation`](#type-da-validation-types-validation-39644) `err`)
* instance [`Applicative`](/appdev/reference/daml-standard-library/prelude#class-da-internal-prelude-applicative-9257) ([`Validation`](#type-da-validation-types-validation-39644) `err`)
* instance [`Semigroup`](/appdev/reference/daml-standard-library/prelude#class-da-internal-prelude-semigroup-78998) ([`Validation`](#type-da-validation-types-validation-39644) `err` `a`)
* instance [`Traversable`](/appdev/reference/daml-standard-library/da-traversable#class-da-traversable-traversable-18144) ([`Validation`](#type-da-validation-types-validation-39644) `err`)
* instance (`Serializable` `err`, `Serializable` `a`) => `Serializable` ([`Validation`](#type-da-validation-types-validation-39644) `err` `a`)
* instance [`Functor`](/appdev/reference/daml-standard-library/prelude#class-ghc-base-functor-31205) ([`Validation`](#type-da-validation-types-validation-39644) `err`)
* instance ([`Eq`](/appdev/reference/daml-standard-library/prelude#class-ghc-classes-eq-22713) `err`, [`Eq`](/appdev/reference/daml-standard-library/prelude#class-ghc-classes-eq-22713) `a`) => [`Eq`](/appdev/reference/daml-standard-library/prelude#class-ghc-classes-eq-22713) ([`Validation`](#type-da-validation-types-validation-39644) `err` `a`)
* instance ([`Show`](/appdev/reference/daml-standard-library/prelude#class-ghc-show-show-65360) `err`, [`Show`](/appdev/reference/daml-standard-library/prelude#class-ghc-show-show-65360) `a`) => [`Show`](/appdev/reference/daml-standard-library/prelude#class-ghc-show-show-65360) ([`Validation`](#type-da-validation-types-validation-39644) `err` `a`)

## Functions

<span id="function-da-validation-invalid-71114" />

### `invalid`

`invalid` : `err` -> [`Validation`](#type-da-validation-types-validation-39644) `err` `a`

Fail for the given reason.

<span id="function-da-validation-ok-57346" />

### `ok`

`ok` : `a` -> [`Validation`](#type-da-validation-types-validation-39644) `err` `a`

Succeed with the given value.

<span id="function-da-validation-validate-15676" />

### `validate`

`validate` : [`Either`](/appdev/reference/daml-standard-library/prelude#type-da-types-either-56020) `err` `a` -> [`Validation`](#type-da-validation-types-validation-39644) `err` `a`

Turn an `Either` into a `Validation`.

<span id="function-da-validation-run-73024" />

### `run`

`run` : [`Validation`](#type-da-validation-types-validation-39644) `err` `a` -> [`Either`](/appdev/reference/daml-standard-library/prelude#type-da-types-either-56020) ([`NonEmpty`](/appdev/reference/daml-standard-library/da-nonempty-types#type-da-nonempty-types-nonempty-16010) `err`) `a`

Convert a `Validation err a` value into an `Either`,
taking the non-empty list of errors as the left value.

<span id="function-da-validation-run1-16566" />

### `run1`

`run1` : [`Validation`](#type-da-validation-types-validation-39644) `err` `a` -> [`Either`](/appdev/reference/daml-standard-library/prelude#type-da-types-either-56020) `err` `a`

Convert a `Validation err a` value into an `Either`,
taking just the first error as the left value.

<span id="function-da-validation-runwithdefault-81974" />

### `runWithDefault`

`runWithDefault` : `a` -> [`Validation`](#type-da-validation-types-validation-39644) `err` `a` -> `a`

Run a `Validation err a` with a default value in case of errors.

<span id="function-da-validation-ltwhatgt-24976" />

### `<?>`

`<?>` : [`Optional`](/appdev/reference/daml-standard-library/prelude#type-da-internal-prelude-optional-37153) `b` -> `err` -> [`Validation`](#type-da-validation-types-validation-39644) `err` `b`

Convert an `Optional t` into a `Validation err t`, or
more generally into an `m t` for any `ActionFail` type `m`.

## Orphan Typeclass Instances

* instance ([`Eq`](/appdev/reference/daml-standard-library/prelude#class-ghc-classes-eq-22713) `err`, [`Eq`](/appdev/reference/daml-standard-library/prelude#class-ghc-classes-eq-22713) `a`) => [`Eq`](/appdev/reference/daml-standard-library/prelude#class-ghc-classes-eq-22713) ([`Validation`](#type-da-validation-types-validation-39644) `err` `a`)

* instance ([`Show`](/appdev/reference/daml-standard-library/prelude#class-ghc-show-show-65360) `err`, [`Show`](/appdev/reference/daml-standard-library/prelude#class-ghc-show-show-65360) `a`) => [`Show`](/appdev/reference/daml-standard-library/prelude#class-ghc-show-show-65360) ([`Validation`](#type-da-validation-types-validation-39644) `err` `a`)

* instance [`Functor`](/appdev/reference/daml-standard-library/prelude#class-ghc-base-functor-31205) ([`Validation`](#type-da-validation-types-validation-39644) `err`)

* instance [`Applicative`](/appdev/reference/daml-standard-library/prelude#class-da-internal-prelude-applicative-9257) ([`Validation`](#type-da-validation-types-validation-39644) `err`)

* instance [`Semigroup`](/appdev/reference/daml-standard-library/prelude#class-da-internal-prelude-semigroup-78998) ([`Validation`](#type-da-validation-types-validation-39644) `err` `a`)

* instance [`Foldable`](/appdev/reference/daml-standard-library/da-foldable#class-da-foldable-foldable-25994) ([`Validation`](#type-da-validation-types-validation-39644) `err`)

* instance [`Traversable`](/appdev/reference/daml-standard-library/da-traversable#class-da-traversable-traversable-18144) ([`Validation`](#type-da-validation-types-validation-39644) `err`)

## History

<div class="x2mdx-ref-history" aria-label="Reference history">
  <div class="x2mdx-ref-history-event x2mdx-ref-history-event--changed" id="history-updated-3-5-1">
    <div class="x2mdx-ref-history-event-head">
      <span class="x2mdx-ref-history-event-label">Updated</span>
      <code class="x2mdx-ref-history-event-version">3.5.1</code>
    </div>

    <p class="x2mdx-ref-history-event-detail">Module declarations or documentation updated.</p>
  </div>

  <div class="x2mdx-ref-history-event x2mdx-ref-history-event--introduced" id="history-added-3-4-9">
    <div class="x2mdx-ref-history-event-head">
      <span class="x2mdx-ref-history-event-label">Added</span>
      <code class="x2mdx-ref-history-event-version">3.4.9</code>
    </div>
  </div>
</div>