TensorBandWindow.prepare: def of stelliferous@0.0.2.0
Import: import stelliferous@0.0.2.0/tensor_band_window.bend as TensorBandWindow
Lines 113-123 of stelliferous@0.0.2.0/tensor_band_window.bend: https://jend.leeeet.dev/read.txt?path=stelliferous@0.0.2.0/tensor_band_window.bend&start_line=113&end_line=123

import Base
import stelliferous@0.0.2.0/tensor_band.bend as Bands
import stelliferous@0.0.2.0/storage_buffer.bend as Storage
import stelliferous@0.0.2.0/traversal_partition.bend as Partition

# The full core tree is threaded through the preparation pass without cloning.
# Each allocation is a requested neighbour range, never a core-sized window.
# The resulting halo tree follows the same layout, ready to pair with cores.
def prepare(~Element: Data,+geometry: Geometry,+fill: Element,layout: Bands.Plan,bands: Bands.Bands(~Element)) -> Bands.Bands(~Element) & Halos(~Element):
  match layout:
    case Bands.Rows{+first,+count}: halo(~Element,input_geometry(geometry),fill,first,count,window(geometry,first,count),bands)
    case Bands.Split{left,right}:
      Storage.bind_pair(~Bands.Bands(~Element),~Halos(~Element),~(Bands.Bands(~Element) & Halos(~Element)),
        prepare(~Element,geometry,fill,left,bands),bands => left =>
          Storage.bind_pair(~Bands.Bands(~Element),~Halos(~Element),~(Bands.Bands(~Element) & Halos(~Element)),
            prepare(~Element,geometry,fill,right,bands),bands => right => (bands,Partition.Fork{left,right})))

Uses (11):
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Pair
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Sigma
  https://jend.leeeet.dev/definition.txt?path=stelliferous@0.0.2.0/storage_buffer.bend&name=bind_pair
  https://jend.leeeet.dev/definition.txt?path=stelliferous@0.0.2.0/tensor_band.bend&name=Bands
  https://jend.leeeet.dev/definition.txt?path=stelliferous@0.0.2.0/tensor_band.bend&name=Plan
  https://jend.leeeet.dev/definition.txt?path=stelliferous@0.0.2.0/tensor_band_window.bend&name=Geometry
  https://jend.leeeet.dev/definition.txt?path=stelliferous@0.0.2.0/tensor_band_window.bend&name=Halos
  https://jend.leeeet.dev/definition.txt?path=stelliferous@0.0.2.0/tensor_band_window.bend&name=halo
  https://jend.leeeet.dev/definition.txt?path=stelliferous@0.0.2.0/tensor_band_window.bend&name=input_geometry
  https://jend.leeeet.dev/definition.txt?path=stelliferous@0.0.2.0/tensor_band_window.bend&name=window
  https://jend.leeeet.dev/definition.txt?path=stelliferous@0.0.2.0/traversal_partition.bend&name=Tree