The internal representation of a Book.

A book with no records. You'll usually want to use this to construct books.

An alias for :-> because otherwise you'll have to tick your constructors.

Key is simply a proxy. You will usually not need to generate it directly, as it is generated by the OverlodadedLabels magic.

Gettable field val book is the constraint needed to get a value of type val from the field field in the book of type Book book.

Get a value by key, if it exists.

>>> get #age julian
28

If the key does not exist, throws a type error >>> get #moneyFrom julian ... ... • The provided Book does not contain the field "moneyFrom" ... Book type: ... '["age" ':-> Int, "name" ':-> String] ... • In the expression: get #moneyFrom julian ...

Flipped and infix version of get.

>>> julian ?: #name
"Julian K. Arni"

'Settable field val old new' is a constraint needed to set the the field field to a value of type val in the book of type 'Book old'. The resulting book will have type 'Book new'.

Sets or updates a field to a value.

>>> set #likesDoctest True julian
Book {age = 28, likesDoctest = True, name = "Julian K. Arni"}

Infix version of set

>>> julian & #age =: 29
Book {age = 29, name = "Julian K. Arni"}

Modifiable field val val' old new is a constraint needed to apply a function of type val -> val' to the field field in the book of type Book old. The resulting book will have type Book new.

Apply a function to a field.

>>> julian & modify #name (fmap toUpper)
Book {age = 28, name = "JULIAN K. ARNI"}

If the key does not exist, throws a type error >>> modify #height (_ -> 132) julian ... ... • The provided Book does not contain the field "height" ... Book type: ... '["age" ':-> Int, "name" ':-> String] ... • In the expression: modify #height ( _ -> 132) julian ...

Infix version of modify.

>>> julian & #name %: fmap toUpper
Book {age = 28, name = "JULIAN K. ARNI"}

Delete a field from a Book, if it exists. If it does not, returns the Book unmodified.

>>> get #name $ delete #name julian
...
...  • The provided Book does not contain the field "name"
...    Book type:
...    '["age" ':-> Int]
...  • In the expression: get #name
...

Generate a Book from an ordinary Haskell record via GHC Generics.

>>> data Test = Test {  field1 :: String, field2 :: Int, field3 :: Char } deriving Generic
>>> fromRecord (Test "hello" 0 'c')
Book {field1 = "hello", field2 = 0, field3 = 'c'}

Trying to convert a datatype which is not a record will result in a type error:

>>> data SomeSumType = LeftSide | RightSide deriving Generic
>>> fromRecord LeftSide
...
... • Cannot convert sum types into Books
...

>>> data Unit = Unit deriving Generic
>>> fromRecord Unit
...
... • Cannot convert non-record types into Books
...