exp5 := int64(0)

	// determine binary or decimal exponent contribution of radix point
	if fcount < 0 {
		// The mantissa has a radix point ddd.dddd; and
		// -fcount is the number of digits to the right
		// of '.'. Adjust relevant exponent accordingly.
		d := int64(fcount)
		switch b {
		case 10:
			exp5 = d
			fallthrough // 10**e == 5**e * 2**e
		case 2:
			exp2 += d
		case 8: