Function gammaCore

src/compute-engine/numerics/special-functions.ts:655–666

(ce: ComputeEngine, z: BigNum)

    if (k > 0 && term.abs().lt(tol)) break;
    result = result.add(term);
    pw = pw._mulToPrecision(u, p);
  }

  return result.sub(logProduct);
}

/**
 * Bignum Gamma function.  Precision scales with BigDecimal.precision.
 *
 * Reflection for z < 0.5; general case delegates to exp(bigGammaln(z)).
 * Note: integer fast paths are in bigGammaln (returning exact ln(n!)).
 * bigGamma goes through exp(ln(...)) so the result is a full-precision float.
 */
export function bigGamma(ce: ComputeEngine, z: BigNum): BigNum {
  // Exact: positive integer → (z-1)! (precision-independent, skip the