Music.Time.Meta

Provides a way to annotate data-types with Transformable meta-data. See Music.Score.Meta for more specific applications.

Inspired by Clojure and Diagram's styles, in turn based on xmonad's Message type, in turn based on ideas in:

Simon Marlow. An Extensible Dynamically-Typed Hierarchy of Exceptions. Proceedings of the 2006 ACM SIGPLAN workshop on Haskell. http://research.microsoft.com/apps/pubs/default.aspx?id=67968.

Attributes

type AttributeClass a = (Typeable a, Monoid a, Semigroup a)

Class of values that can be wrapped.

type TAttributeClass a = (Transformable a, AttributeClass a)

Class of values that can be wrapped and transformed.

data Attribute

An existential wrapper type to hold attributes.

Instances

Semigroup Attribute

Transformable Attribute

Splittable Attribute

Reversible Attribute

Creating attributes

wrapAttr :: AttributeClass a => a -> Attribute

Wrap up an attribute.

wrapTAttr :: TAttributeClass a => a -> Attribute

Wrap up a transformable attribute.

unwrapAttr :: AttributeClass a => Attribute -> Maybe a

Convert something from an attribute. Also works with transformable attributes

Meta-data

data Meta

Instances

Show Meta

Monoid Meta

The empty meta contains no attributes; composition of metas is a union of attributes; if the two metas have attributes of the same type they are combined according to their semigroup structure.

Semigroup Meta

Transformable Meta

Splittable Meta

Reversible Meta

HasMeta Meta

Creating meta-data

wrapMeta :: forall a. AttributeClass a => a -> Meta

Convert something from meta-data. Also works with transformable attributes

wrapTMeta :: forall a. TAttributeClass a => a -> Meta

Convert something to meta-data.

unwrapMeta :: forall a. AttributeClass a => Meta -> Maybe a

Convert something from meta-data.

The HasMeta class

class HasMeta a where

Type class for things which have meta-data.

Methods

meta :: Lens' a Meta

Access the meta-data.

Instances

HasMeta Meta

HasMeta a => HasMeta (Maybe a)

HasMeta (AddMeta a)

HasMeta (Score a)

HasMeta a => HasMeta (b, a)

HasMeta a => HasMeta (Twain b a)

setMeta :: HasMeta a => Meta -> a -> a

setMetaAttr :: (AttributeClass b, HasMeta a) => b -> a -> a

Update a meta attribute.

setMetaTAttr :: (TAttributeClass b, HasMeta a) => b -> a -> a

Update a meta attribute.

applyMeta :: HasMeta a => Meta -> a -> a

Apply meta-information by combining it (on the left) with the existing meta-information.

Add meta-data to arbitrary types

data AddMeta a

Annotate an arbitrary type with meta-data, preserving instances of all common type classes. In particular Functor and Applicative is lifted and Compose AddMeta is semantically equivalent to Identity.

Instances

Monad AddMeta

Functor AddMeta

Typeable1 AddMeta

Applicative AddMeta

Foldable AddMeta

Comonad AddMeta

Bounded a => Bounded (AddMeta a)

Enum a => Enum (AddMeta a)

Eq a => Eq (AddMeta a)

Floating a => Floating (AddMeta a)

Fractional a => Fractional (AddMeta a)

Integral a => Integral (AddMeta a)

Num a => Num (AddMeta a)

Ord a => Ord (AddMeta a)

Real a => Real (AddMeta a)

RealFrac a => RealFrac (AddMeta a)

Show a => Show (AddMeta a)

Monoid a => Monoid (AddMeta a)

Semigroup a => Semigroup (AddMeta a)

Wrapped (AddMeta a)

Transformable a => Transformable (AddMeta a)

HasDuration a => HasDuration (AddMeta a)

HasPosition a => HasPosition (AddMeta a)

Splittable a => Splittable (AddMeta a)

Reversible a => Reversible (AddMeta a)

HasMeta (AddMeta a)

Rewrapped (AddMeta a) (AddMeta b)

annotated :: Lens (AddMeta a) (AddMeta b) a b

Access the annotated value.

 over annotated = fmap

unannotated :: Getter a (AddMeta a)

Access the annotated value.

 view fromAnnotated = pure

unsafeAnnotated :: Iso (AddMeta a) (AddMeta b) a b

Access the annotated value. This is only an isomorphism up to meta-data equivalence. In particular under unsafeAnnotated leads to meta-data being thrown away. See annotated and unannotated for safe (but less general) definitions.

 over annotated = fmap