Commit 05380a11a426ce22a1a27f47d9f9371a72a35e24 | zig

author	Filippo Casarin <casarin.filippo17@gmail.com> 2021-03-24 20:59:15+01:00
committer	Andrew Kelley <andrew@ziglang.org> 2021-06-10 10:20:09-07:00
log	05380a11a426ce22a1a27f47d9f9371a72a35e24
tree	147ea450a01d2f40d7892ba3825d3a99bc149934
parent	4a3ac16711b41d90e0666f478e3085f764c83208

std.math.sqrt_int: fixed odd size integers types

1 files changed, 26 insertions(+), 31 deletions(-)

lib
- std
  - math
    sqrt.zig

lib/std/math/sqrt.zig+26-31

...	...	@@ -39,55 +39,50 @@ pub fn sqrt(x: anytype) Sqrt(@TypeOf(x)) {
39	39	}
40	40
41	41	fn sqrt_int(comptime T: type, value: T) Sqrt(T) {
42		switch (T) {
43		u0 => return 0,
44		u1 => return value,
45		else => {},
46		}
47
48		var op = value;
49		var res: T = 0;
50		var one: T = 1 << (@typeInfo(T).Int.bits - 2);
	42	if (@typeInfo(T).Int.bits <= 2) {
	43	return if (value == 0) 0 else 1; // shortcut for small number of bits to simplify general case
	44	} else {
	45	var op = value;
	46	var res: T = 0;
	47	var one: T = 1 << ((@typeInfo(T).Int.bits - 1) & -2); // highest power of four that fits into T
51	48
52		// "one" starts at the highest power of four <= than the argument.
53		while (one > op) {
54		one >>= 2;
55		}
	49	// "one" starts at the highest power of four <= than the argument.
	50	while (one > op) {
	51	one >>= 2;
	52	}
56	53
57		while (one != 0) {
58		if (op >= res + one) {
59		op -= res + one;
60		res += 2 * one;
	54	while (one != 0) {
	55	var c = op >= res + one;
	56	if (c) op -= res + one;
	57	res >>= 1;
	58	if (c) res += one;
	59	one >>= 2;
61	60	}
62		res >>= 1;
63		one >>= 2;
64		}
65	61
66		const ResultType = Sqrt(T);
67		return @intCast(ResultType, res);
	62	return @intCast(Sqrt(T), res);
	63	}
68	64	}
69	65
70	66	test "math.sqrt_int" {
71		try expect(sqrt_int(u0, 0) == 0);
72		try expect(sqrt_int(u1, 1) == 1);
73	67	try expect(sqrt_int(u32, 3) == 1);
74	68	try expect(sqrt_int(u32, 4) == 2);
75	69	try expect(sqrt_int(u32, 5) == 2);
76	70	try expect(sqrt_int(u32, 8) == 2);
77	71	try expect(sqrt_int(u32, 9) == 3);
78	72	try expect(sqrt_int(u32, 10) == 3);
	73
	74	try expect(sqrt_int(u0, 0) == 0);
	75	try expect(sqrt_int(u1, 1) == 1);
	76	try expect(sqrt_int(u2, 3) == 1);
	77	try expect(sqrt_int(u3, 4) == 2);
	78	try expect(sqrt_int(u4, 8) == 2);
	79	try expect(sqrt_int(u4, 9) == 3);
79	80	}
80	81
81	82	/// Returns the return type `sqrt` will return given an operand of type `T`.
82	83	pub fn Sqrt(comptime T: type) type {
83	84	return switch (@typeInfo(T)) {
84		.Int => \|int\| {
85		return switch (int.bits) {
86		0 => u0,
87		1 => u1,
88		else => std.meta.Int(.unsigned, int.bits / 2),
89		};
90		},
	85	.Int => \|int\| std.meta.Int(.unsigned, (int.bits + 1) / 2),
91	86	else => T,
92	87	};
93	88	}