return o
}

func compact(o options) options {
	o.simple = true
	return o
}

// HandleFinalSigma specifies whether the special handling of Greek final sigma
// should be enabled. Unicode prescribes handling the Greek final sigma for all
// locales, but standards like IDNA and PRECIS override this default.
func HandleFinalSigma(enable bool) Option {
	if enable {
		return handleFinalSigma
	}

		if !c.next() {
			break
		}
		if wasMid && c.info.isMid() {
			c.isMidWord = false
		}
	}
	return c.retSpan()
}

// finalSigma adds Greek final Sigma handing to another casing function. It
// determines whether a lowercased sigma should be σ or ς, by looking ahead for
// case-ignorables and a cased letters.
func finalSigma(f mapFunc) mapFunc {
	return func(c *context) bool {
		if !c.hasPrefix("Σ") {

// What we want to calculate is: R = matmul(P-z, Q-w).
// Then r_ij = sigma(k) (p_ik - z) * (q_kj - w)
//           = sigma(k)(p_ik * q_kj) - w * sigma(k)p_ik - z * sigma(k)q_kj
//             + sigma(k)z*w.
// zp_input_contribution = z * sigma(k)q_kj
// zp_weight_contribution = w * sigma(k)p_ik
// In case z != 0 and w != 0, we need to additionally calculate sigma(k)z*w,
// which is: # of reduced dim(n in this case) * input_zp * weight_zp

        entities.put("Nu", "\u039d");
        entities.put("Xi", "\u039e");
        entities.put("Omicron", "\u039f");
        entities.put("Pi", "\u03a0");
        entities.put("Rho", "\u03a1");
        entities.put("Sigma", "\u03a3");
        entities.put("Tau", "\u03a4");
        entities.put("Upsilon", "\u03a5");
        entities.put("Phi", "\u03a6");
        entities.put("Chi", "\u03a7");
        entities.put("Psi", "\u03a8");

		default:
			t.Fatalf("unexpected value %d on channel", b)
		}
	}
	// If the select in the goroutine is fair,
	// cnt1 and cnt2 should be about the same value.
	// See if we're more than 10 sigma away from the expected value.
	// 10 sigma is a lot, but we're ok with some systematic bias as
	// long as it isn't too severe.
	const mean = trials * 0.5
	const variance = trials * 0.5 * (1 - 0.5)
	stddev := math.Sqrt(variance)

        entities.put("Nu", "\u039d");
        entities.put("Xi", "\u039e");
        entities.put("Omicron", "\u039f");
        entities.put("Pi", "\u03a0");
        entities.put("Rho", "\u03a1");
        entities.put("Sigma", "\u03a3");
        entities.put("Tau", "\u03a4");
        entities.put("Upsilon", "\u03a5");
        entities.put("Phi", "\u03a6");
        entities.put("Chi", "\u03a7");
        entities.put("Psi", "\u03a8");

	"↓":                  "\u2193",
	"←":                  "\u2190",
	"→":                 "\u2192",
	"↑":                    "\u2191",
	"Σ":                           "\u03a3",
	"∘":                     "\u2218",
	"𝕊":                            "\U0001d54a",
	"√":                            "\u221a",

037A          ; disallowed_STD3_mapped ; 0020 03B9     # 1.1  GREEK YPOGEGRAMMENI
037B..037D    ; valid                                  # 5.0  GREEK SMALL REVERSED LUNATE SIGMA SYMBOL..GREEK SMALL REVERSED DOTTED LUNATE SIGMA SYMBOL
037E          ; disallowed_STD3_mapped ; 003B          # 1.1  GREEK QUESTION MARK
037F          ; mapped                 ; 03F3          # 7.0  GREEK CAPITAL LETTER YOT

	"Kappa":    "\u039A",
	"Lambda":   "\u039B",
	"Mu":       "\u039C",
	"Nu":       "\u039D",
	"Xi":       "\u039E",
	"Omicron":  "\u039F",
	"Pi":       "\u03A0",
	"Rho":      "\u03A1",
	"Sigma":    "\u03A3",
	"Tau":      "\u03A4",
	"Upsilon":  "\u03A5",
	"Phi":      "\u03A6",
	"Chi":      "\u03A7",
	"Psi":      "\u03A8",
	"Omega":    "\u03A9",
	"alpha":    "\u03B1",
	"beta":     "\u03B2",

// Analysis series B. Vol. 1:
// lgamma(z + 1) = (log(2) + log(pi)) / 2 + (z + 1/2) * log(t(z)) - t(z) + A(z)
// t(z) = z + kLanczosGamma + 1/2
// A(z) = kBaseLanczosCoeff
//       + sigma(k = 1, n, kLanczosCoefficients[i] / (z +  k))
//
// Coefficients for the Lanczos approximation of the gamma function. The
// coefficients are uniquely determined by the choice of g and n