7GUIs — Cells

How it works

Every cell's value is a derive that parses its formula and resolves references by reading other cells' derives — so dependency tracking is automatic and exact. Edit A1 and only formulas that (transitively) mention A1 recompute; unrelated cells never even re-parse (the test counts evaluations). A formula whose result didn't change wakes nobody downstream, and reference cycles come back as #CYCLE instead of a hang.

const d = derive((): CellValue => {
  const src = formulas()[key] ?? ''    // tracked read: exactly this cell's path
  if (!src.startsWith('=')) return literalOrText(src)
  return parseExpr(tokenize(src), (ref) => numberOf(valueOf(ref)()))
})