Hylograph.Expr.Integration

evalAttr :: forall datum a. Show a => String -> EvalD datum a -> Attribute datum

Convert a datum expression to a data-driven attribute.

The expression is interpreted using EvalD, which produces a function from (datum, index) to the attribute value.

-- expression
scaleX :: forall repr. NumExpr repr => DatumExpr repr PointRow => repr Number
scaleX = xField *: 20.0 +: 200.0

-- attribute
cxAttr :: Attribute Point
cxAttr = evalAttr "cx" scaleX

evalAttrStr :: forall datum. String -> EvalD datum String -> Attribute datum

Convert a string expression to an attribute (no quoting)

Use this for string-valued attributes like fill, stroke, class, d, etc.

evalAttrIndexed :: forall datum a. Show a => String -> EvalD datum a -> Attribute datum

Convert an expression to an indexed attribute.

Use this when your expression uses the datum index (e.g., for staggered positioning or animation delays).

-- expression using index
xFromIndex :: forall repr. NumExpr repr => DatumExpr repr PointRow => repr Number
xFromIndex = indexNum *: 50.0 +: 25.0
  where indexNum = E.mul (n 1.0) (unsafeCoerce index)  -- Convert Int to Number

-- indexed attribute
xAttr :: Attribute Point
xAttr = evalAttrIndexed "x" xFromIndex

evalAttrIndexedStr :: forall datum. String -> EvalD datum String -> Attribute datum

Convert an indexed string expression to an attribute (no quoting)

staticNum :: forall datum a. Show a => String -> a -> Attribute datum

Create a static numeric attribute.

For expressions that don't depend on datum at all, this produces a StaticAttr which is more efficient (evaluated once, not per-element).

staticStr :: forall datum. String -> String -> Attribute datum

Create a static string attribute (no quoting)

liftFn :: forall datum a. (datum -> a) -> EvalD datum a

Lift a datum-dependent PureScript function to an EvalD expression

This is an escape hatch for complex computations that can't easily be expressed in the DSL.

linePath :: Series -> String
linePath s = ...complex path computation...

d (liftFn linePath)

liftFnI :: forall datum a. (datum -> Int -> a) -> EvalD datum a

Lift an indexed PureScript function to an EvalD expression

fnAttr :: forall datum a. Show a => String -> (datum -> a) -> Attribute datum

Create a data-driven attribute from a plain PureScript function

Shortcut for evalAttr name (liftFn f)

fnAttrStr :: forall datum. String -> (datum -> String) -> Attribute datum

Create a string data-driven attribute from a plain PureScript function

Shortcut for evalAttrStr name (liftFn f)

fnAttrI :: forall datum a. Show a => String -> (datum -> Int -> a) -> Attribute datum

Create an indexed attribute from a plain PureScript function (datum -> Int -> a)

Use this when you need both datum and index access

fnAttrIStr :: forall datum. String -> (datum -> Int -> String) -> Attribute datum

Create an indexed string attribute from a plain PureScript function

evalAttrs :: forall datum a. Show a => Array { expr :: EvalD datum a, name :: String } -> Array (Attribute datum)

Convert multiple expressions to attributes at once.

This is a convenience for defining attribute sets:

circleAttrs :: Array (Attribute Point)
circleAttrs = evalAttrs
  [ { name: "cx", expr: scaleX }
  , { name: "cy", expr: scaleY }
  , { name: "r", expr: radius }
  ]

data AttributeValue

Attribute values

We support the most common value types. The ADT ensures type safety when setting attributes.

Constructors

• StringValue String
• NumberValue Number
• BooleanValue Boolean

Instances

• Eq AttributeValue
• Ord AttributeValue
• Show AttributeValue

newtype AttributeName

Attribute names (SVG/HTML properties)

We use a newtype to prevent typos and enable IDE autocomplete. The String inside is the actual DOM attribute name.

Constructors

• AttributeName String

Instances

• Eq AttributeName
• Ord AttributeName
• Show AttributeName

data Attribute datum

Type-safe attribute with datum phantom type

Attributes can be:

• Static: Same value for all elements
• Data-driven: Value computed from datum (with source metadata)
• Indexed: Value computed from datum and index (with source metadata)

The phantom type datum ensures attributes are only applied to selections with matching data types.

The AttrSource field enables interpreters to inspect attribute origins without evaluating the functions.

Constructors

• StaticAttr AttributeName AttributeValue
• DataAttr AttributeName AttrSource (datum -> AttributeValue)
• IndexedAttr AttributeName AttrSource (datum -> Int -> AttributeValue)
• AnimatedAttr { config :: AnimationConfig, fromValue :: Maybe (AnimatedValue datum), name :: AttributeName, toValue :: AnimatedValue datum }
• AnimatedCompound { config :: AnimationConfig, fromValues :: Array (AnimatedValue datum), generator :: Array Number -> String, name :: AttributeName, toValues :: Array (AnimatedValue datum) }

  Animated compound attribute for paths and other generated strings

  Animates multiple numeric values and calls a generator function to produce the final string value. Used for:

  • linkVertical (4 numbers → path string)
  • sankeyLink (6 numbers → path string)
  • arc (4 numbers → arc path)

  The generator receives interpolated values in the same order as fromValues/toValues.

Instances

• Show (Attribute datum)
• Contravariant Attribute

  Contravariant instance for Attribute

  Attributes consume data (they're data sinks), making them naturally contravariant. This enables attribute reuse via cmap:

  -- Define attribute for specific type
  radiusAttr :: Attribute Number
  radiusAttr = DataAttr (AttributeName "r") NumberValue
  
  -- Adapt to work with richer type
  type Circle = { radius :: Number, x :: Number, y :: Number }
  circleRadiusAttr :: Attribute Circle
  circleRadiusAttr = cmap _.radius radiusAttr
  

  The key insight: cmap composes the projection function with the attribute's data accessor, allowing attributes written for simple types to work with complex types via field selection.

data AttrSource

Source metadata for attributes

Describes where the attribute value comes from, enabling interpreters like MetaAST to show meaningful information about attribute bindings.

This is automatically captured when using the DSL (field, num, etc.) but is UnknownSource for raw PureScript functions (escape hatches).

Constructors

• UnknownSource
• StaticSource String
• FieldSource String
• ExprSource String
• IndexSource
• OpaqueSource

Instances

• Eq AttrSource
• Ord AttrSource
• Show AttrSource