ScalarExpr

Wire-serialisable AST for scalar expressions over the per-update input environment. The library uses these wherever a stat needs to apply a caller-supplied projection / weight / threshold expression that has to round-trip on the wire; weightBy, transform, the per-bin scaler projections, the WithFeedback op, the loss / pinball / quantile configurations.

The input environment

Every evaluation receives:

• x: Double: the primary scalar input. For series stats it's the observation value; for paired stats it's the x-axis; for regression stats it's unused (use V to access feature vector coordinates).

• y: Double: the secondary scalar input. Used by paired stats (the y-axis) and regression stats (the response).

• v: DoubleArray: the full input vector. Used by vector / regression stats; empty otherwise.

• primary: Result?: the primary stat's snapshot at evaluation time for feedback operators. Center, Scale, Low, High read directly from this; per-coordinate ops receive an com.eignex.kumulant.core.IndexedResult to thread the coordinate index through.

Stats that don't need a particular field pass the default (0.0, empty array, null).

Construction

Compose with the DSL operators in this file rather than constructing AST data classes directly: X * 2.0, (X + Const(1.0)) gt 0.0, IfExpr(X gt 0.0, X, -X). The operators return the public sealed interface and hide the concrete (internal) node types.

Wire format

Polymorphic via skema's $type discriminator. The @SerialName on each concrete node is the wire-format tag; pick stable, unambiguous names if you add new ones.

Inheritors