Module activation 

The activation runtime for for traversals (for_traversal.md §3.4, §3.6, §5).

A TraversalStream dispenses one Activation per tuple of a compiled traversal. An activation is a fresh state over the body’s program, compiled once at parent compile time, with the tuple’s elements and the parent’s cascaded wires bound and every over cursor narrowed. Activation never compiles: the cost of the second activation is the cost of the first minus nothing, because the first did not compile either.

Cycles follow the rule in §3.4: a body with a cursor iterates its narrowest cursor extent, one cycle per ordinal, with the cursor’s ordinal written before each pull; a body without a cursor has one cycle per activation.

Structs

Activation

One child scope of a traversal: the tuple it was activated for, a fresh kernel over the body’s program, and its cursor slice if the body declares a cursor.

CursorSlice

The interval of ordinals an activation’s cursor iterates.

TraversalStream

Dispenses activations for one traversal of a kernel.

Functions

open_traversal

Open traversal against parent’s current values, on any engine (engines.md §3.6): the cascaded wires and the wires the sources reference are snapshotted through the Kernel trait, and the comprehension is evaluated in the body’s scope, the body’s program with those wires bound, where a source or predicate resolves every name it can reference and a tuple’s own elements are layered in front as it is built. Nothing here needs the opening kernel beyond the snapshot.

program_identity

Identity of the program an activation runs over, for callers that want to assert the one-program-per-position property.