Function canonicalAngle

src/compute-engine/boxed-expression/utils.ts:185–204

(
  x: Expression | undefined
)

 */
const TRANSFORMER_HEADS = new Set([
  'Simplify',
  'Expand',
  'ExpandAll',
  'Factor',
  'Together',
  'Distribute',
  'TrigExpand',
]);

/**
 * Reduce a held (already canonical) operand whose head is an
 * expression-transformer (see `TRANSFORMER_HEADS`) so that a structural
 * algorithm sees the transformed expression rather than the transformer
 * call. Any other expression is returned unchanged.
 */
export function reduceTransformerHead(expr: Expression): Expression {
  return reduceTransformerHeads(inlineLambdaApplications(expr));
}

/**
 * Reduce transformer heads anywhere in `expr`, not only at its root: in
 * `Solve(Simplify(u) = 2, w)` the transformer sits inside the `Equal`, so a
 * root-only check left it opaque and the solve returned `[]`.