Struct TraversalStream 

pub struct TraversalStream { /* private fields */ }

Dispenses activations for one traversal of a kernel.

The stream holds the comprehension’s tuples addressed by position (IndexedTuples): opening evaluated every source, and each activation computes its own tuple, so len, seek, and activation(index) cost the same at any index, and an order’s selection over a large product holds only the selected positions.

Implementations

impl TraversalStream

pub fn len(&self) -> usize

Number of activations the traversal dispenses.

pub fn is_empty(&self) -> bool

Whether the traversal dispenses no activation.

pub fn traversal(&self) -> &Traversal

The traversal this stream dispenses.

pub fn seek(&mut self, index: usize)

Move the dispense position. Every strategy is a decidable permutation, so seeking costs nothing beyond the index.

pub fn position(&self) -> usize

Current dispense position.

pub fn engine(&self) -> Engine

The engine this stream’s activations run on: the engine of the kernel that opened the traversal.

pub fn body_program(&self) -> Result<Arc<dyn KernelProgram>, String>

The body’s program on this stream’s engine — the one every activation is a kernel over, compiled once and shared, which is what makes activation cost no compile.

pub fn advance(&mut self) -> Result<Option<Activation<Box<dyn Kernel>>>, String>

The next activation, or None when exhausted.

pub fn activation( &self, index: usize, ) -> Result<Activation<Box<dyn Kernel>>, String>

Build the activation at index without moving the dispense position. Fibers partition a traversal by calling this over disjoint index ranges.

The kernel is on the stream’s engine — the one the kernel that opened the traversal runs on.

pub fn activation_on( &self, index: usize, engine: Engine, ) -> Result<Activation<Box<dyn Kernel>>, String>

Self::activation on engine (engines.md §3.6): a fresh kernel over the body’s program for that engine, compiled once per engine and shared by every activation after, driven through the Kernel trait with the same elements, cascade, and cursor narrowing. An engine that cannot run the body says so by name.