Jpeg.jpeg.history.valid: def of gralha-jpeg-decode@0.1.0.1
Import: import gralha-jpeg-decode@0.1.0.1/jpeg.bend as Jpeg
Lines 535-540 of gralha-jpeg-decode@0.1.0.1/jpeg.bend: https://jend.leeeet.dev/read.txt?path=gralha-jpeg-decode@0.1.0.1/jpeg.bend&start_line=535&end_line=540

import Base
import gralha-text-scan@0.1.0.1/scan.bend as U
import gralha-bytes@0.1.0.1/bytes.bend as Bin

# The sample buffer holds approximation history until IDCT replaces it.
# Zero means unseen; low+1 records the last transmitted coefficient bit.
def jpeg.history.valid(n: Nat, +index: U32, +history: Bin.Bytes, +high: U32) -> Bool:
  match n:
    case 0n: True{}
    case 1n+d: U32.is_eq(Bin.bytes.get(history, index), U.choose(U32, U32.is_eq(high, 0), 0, U32.inc(high))) && jpeg.history.valid(d, U32.inc(index), history, high)

Uses (9):
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Bool
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Bool.and
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Nat
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=U32
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=U32.inc
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=U32.is_eq
  https://jend.leeeet.dev/definition.txt?path=gralha-bytes@0.1.0.1/bytes.bend&name=Bytes
  https://jend.leeeet.dev/definition.txt?path=gralha-bytes@0.1.0.1/bytes.bend&name=bytes.get
  https://jend.leeeet.dev/definition.txt?path=gralha-text-scan@0.1.0.1/scan.bend&name=choose