// borderline - too large
		{"+0x1.fffffffffffff8p1023", infp0, ErrRange},
		{"-0x1fffffffffffff.8p+971", infm0, ErrRange},
		{"+0x1.fffffffffffff8p1023i", inf0p, ErrRange},
		{"-0x1fffffffffffff.8p+971i", inf0m, ErrRange},
		{"+0x1.fffffffffffff8p1023+0x1.fffffffffffff8p1023i", infpp, ErrRange},
		{"+0x1.fffffffffffff8p1023-0x1.fffffffffffff8p1023i", infpm, ErrRange},

	{"1.797693134862315808e308", "+Inf", ErrRange},
	{"-1.797693134862315808e308", "-Inf", ErrRange},
	{"0x1.fffffffffffff8p1023", "+Inf", ErrRange},
	{"-0x1.fffffffffffff8p1023", "-Inf", ErrRange},
	{"0x1fffffffffffff.8p+971", "+Inf", ErrRange},
	{"-0x1fffffffffffff8p+967", "-Inf", ErrRange},
	{"0x.1fffffffffffff8p1027", "+Inf", ErrRange},
	{"-0x.1fffffffffffff9p1027", "-Inf", ErrRange},

	// a little too large

		{"1", 1, Exact},
		{"1.000000000000000000001", 1, Below},
		{"12345.0", 12345, Exact},
		{"12345.000000000000000000001", 12345, Below},
		{"0x1.fffffffffffff0p1023", math.MaxFloat64, Exact},
		{"0x1.fffffffffffff4p1023", math.MaxFloat64, Below},

		// overflow
		{"0x1.fffffffffffff8p1023", math.Inf(+1), Above},
		{"0x1p1024", math.Inf(+1), Above},
		{"1e10000", math.Inf(+1), Above},

	assert(equal(0x2.p10, 2048.0))
	assert(equal(0x1.Fp+0, 1.9375))
	assert(equal(0x.8p-0, 0.5))
	assert(equal(0x1FFFp-16, 0.1249847412109375))
	assert(equal(0x1.fffffffffffffp1023, 1.7976931348623157e308))
	assert(equal(0x1.fffffffffffffp1023i, complex(0, 1.7976931348623157e308)))

	assert(equal(0x_1p-2, 0.25))
	assert(equal(0x2.p1_0, 2048.0))
	assert(equal(0x1_0.Fp+0, 16.9375))
	assert(equal(0x_0.8p-0, 0.5))

// no prefix is accepted. The octal prefix "0" is not supported (a leading
// "0" is simply considered a "0").
//
// A "p" or "P" exponent indicates a base 2 (rather than base 10) exponent;
// for instance, "0x1.fffffffffffffp1023" (using base 0) represents the
// maximum float64 value. For hexadecimal mantissae, the exponent character
// must be one of 'p' or 'P', if present (an "e" or "E" exponent indicator

		{"0x0p+10", 0},
		{"-0x0p-10", -zero_},
		{"0xff", 255},
		{"0X.8p1", 1},
		{"-0X0.00008p16", -0.5},
		{"-0X0.00008P+16", -0.5},
		{"0x0.0000000000001p-1022", math.SmallestNonzeroFloat64},
		{"0x1.fffffffffffffp1023", math.MaxFloat64},

		// underscores
		{"0_0", 0},
		{"1_000.", 1000},
		{"1_2_3.4_5_6", 123.456},
		{"1.0e0_0", 1},
		{"1p+1_0", 1024},
		{"0b_1000", 0x8},
		{"0b_1011_1101", 0xbd},