Record.Builder

newtype Builder a b

A Builder can be used to build a record by incrementally adding fields in-place, instead of using insert and repeatedly generating new immutable records which need to be garbage collected.

The mutations accumulated in a Builder are safe because intermediate states can't be observed. These mutations, then, are performed all-at-once in the build function.

The Category instance for Builder can be used to compose builders.

For example:

build (insert x 42 >>> insert y "testing") {} :: { x :: Int, y :: String }

Instances

• Semigroupoid Builder
• Category Builder

build :: forall r1 r2. Builder (Record r1) (Record r2) -> Record r1 -> Record r2

Build a record, starting from some other record.

buildFromScratch :: forall r. Builder (Record ()) (Record r) -> Record r

Build a record from scratch.

flip :: forall r1 r2 r3. (Record r1 -> Builder (Record r2) (Record r3)) -> Record r2 -> Builder (Record r1) (Record r3)

Flip a function of one argument returning a builder.

insert :: forall l a r1 r2. Cons l a r1 r2 => Lacks l r1 => IsSymbol l => Proxy l -> a -> Builder (Record r1) (Record r2)

Build by inserting a new field.

modify :: forall l a b r r1 r2. Cons l a r r1 => Cons l b r r2 => IsSymbol l => Proxy l -> (a -> b) -> Builder (Record r1) (Record r2)

Build by modifying an existing field.

delete :: forall l a r1 r2. IsSymbol l => Lacks l r1 => Cons l a r1 r2 => Proxy l -> Builder (Record r2) (Record r1)

Build by deleting an existing field.

rename :: forall l1 l2 a r1 r2 r3. IsSymbol l1 => IsSymbol l2 => Cons l1 a r2 r1 => Lacks l1 r2 => Cons l2 a r2 r3 => Lacks l2 r2 => Proxy l1 -> Proxy l2 -> Builder (Record r1) (Record r3)

Build by renaming an existing field.

merge :: forall r1 r2 r3 r4. Union r1 r2 r3 => Nub r3 r4 => Record r1 -> Builder (Record r2) (Record r4)

Build by merging existing fields from another record, taking precedence in the case of overlaps.

For example:

build (merge { x: 1, y: "y" }) { y: 2, z: true }
 :: { x :: Int, y :: String, z :: Boolean }

union :: forall r1 r2 r3. Union r1 r2 r3 => Record r1 -> Builder (Record r2) (Record r3)

Build by merging existing fields from another record, taking precedence in the case of overlaps. Unlike merge, this does not remove duplicate labels from the resulting record type. This can result in better inference for some pipelines, deferring the need for a Nub constraint.

For example:

build (union { x: 1, y: "y" }) { y: 2, z: true }
 :: { x :: Int, y :: String, y :: Int, z :: Boolean }

disjointUnion :: forall r1 r2 r3. Union r1 r2 r3 => Nub r3 r3 => Record r1 -> Builder (Record r2) (Record r3)

Build by merging some disjoint set of fields from another record.

nub :: forall r1 r2. Nub r1 r2 => Builder (Record r1) (Record r2)

A coercion which removes duplicate labels from a record's type.