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add std.math.sign

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Travis Staloch 2022-05-11 16:33:55 -07:00 committed by Andrew Kelley
parent 5c20c7036b
commit 974af5f291
1 changed files with 112 additions and 3 deletions
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115
lib/std/math.zig
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@ -611,15 +611,15 @@ pub fn IntFittingRange(comptime from: comptime_int, comptime to: comptime_int) t
if (from == 0 and to == 0) {
return u0;
}
const sign: std.builtin.Signedness = if (from < 0) .signed else .unsigned;
const signedness: std.builtin.Signedness = if (from < 0) .signed else .unsigned;
const largest_positive_integer = max(if (from < 0) (-from) - 1 else from, to); // two's complement
const base = log2(largest_positive_integer);
const upper = (1 << base) - 1;
var magnitude_bits = if (upper >= largest_positive_integer) base else base + 1;
if (sign == .signed) {
if (signedness == .signed) {
magnitude_bits += 1;
}
return std.meta.Int(sign, magnitude_bits);
return std.meta.Int(signedness, magnitude_bits);
}
test "IntFittingRange" {
@ -1447,3 +1447,112 @@ pub fn break_f80(x: f80) F80 {
.exp = @truncate(u16, int >> 64),
};
}
/// Returns -1, 0, or 1.
/// Supports integer types, vectors of integer types, and float types.
/// Unsigned integer types will always return 0 or 1.
/// TODO: support vectors of floats
/// Branchless.
pub inline fn sign(i: anytype) @TypeOf(i) {
const T = @TypeOf(i);
return switch (@typeInfo(T)) {
.Int, .ComptimeInt => @as(T, @boolToInt(i > 0)) - @boolToInt(i < 0),
.Float, .ComptimeFloat => @intToFloat(T, @boolToInt(i > 0)) - @intToFloat(T, @boolToInt(i < 0)),
.Vector => |vinfo| blk: {
const u1xN = std.meta.Vector(vinfo.len, u1);
break :blk switch (@typeInfo(vinfo.child)) {
.Int => @as(T, @bitCast(u1xN, i > @splat(vinfo.len, @as(vinfo.child, 0)))) -
@as(T, @bitCast(u1xN, i < @splat(vinfo.len, @as(vinfo.child, 0)))),
.Float => @compileError("TODO: add support for vectors of floats once @intToFloat accepts vector types"),
// break :blk @intToFloat(T, @bitCast(u1xN, i > @splat(vinfo.len, @as(vinfo.child, 0)))) -
// @intToFloat(T, @bitCast(u1xN, i < @splat(vinfo.len, @as(vinfo.child, 0)))),
else => @compileError("Expected vector of ints or floats, found " ++ @typeName(T)),
};
},
else => @compileError("Expected an int, float or vector of one, found " ++ @typeName(T)),
};
}
fn testSign() !void {
// each of the following blocks checks the inputs
// 2, -2, 0, { 2, -2, 0 } provide expected output
// 1, -1, 0, { 1, -1, 0 } for the given T
// (negative values omitted for unsigned types)
{
const T = i8;
try std.testing.expectEqual(@as(T, 1), sign(@as(T, 2)));
try std.testing.expectEqual(@as(T, -1), sign(@as(T, -2)));
try std.testing.expectEqual(@as(T, 0), sign(@as(T, 0)));
try std.testing.expectEqual(@Vector(3, T){ 1, -1, 0 }, sign(@Vector(3, T){ 2, -2, 0 }));
}
{
const T = i32;
try std.testing.expectEqual(@as(T, 1), sign(@as(T, 2)));
try std.testing.expectEqual(@as(T, -1), sign(@as(T, -2)));
try std.testing.expectEqual(@as(T, 0), sign(@as(T, 0)));
try std.testing.expectEqual(@Vector(3, T){ 1, -1, 0 }, sign(@Vector(3, T){ 2, -2, 0 }));
}
{
const T = i64;
try std.testing.expectEqual(@as(T, 1), sign(@as(T, 2)));
try std.testing.expectEqual(@as(T, -1), sign(@as(T, -2)));
try std.testing.expectEqual(@as(T, 0), sign(@as(T, 0)));
try std.testing.expectEqual(@Vector(3, T){ 1, -1, 0 }, sign(@Vector(3, T){ 2, -2, 0 }));
}
{
const T = u8;
try std.testing.expectEqual(@as(T, 1), sign(@as(T, 2)));
try std.testing.expectEqual(@as(T, 0), sign(@as(T, 0)));
try std.testing.expectEqual(@Vector(2, T){ 1, 0 }, sign(@Vector(2, T){ 2, 0 }));
}
{
const T = u32;
try std.testing.expectEqual(@as(T, 1), sign(@as(T, 2)));
try std.testing.expectEqual(@as(T, 0), sign(@as(T, 0)));
try std.testing.expectEqual(@Vector(2, T){ 1, 0 }, sign(@Vector(2, T){ 2, 0 }));
}
{
const T = u64;
try std.testing.expectEqual(@as(T, 1), sign(@as(T, 2)));
try std.testing.expectEqual(@as(T, 0), sign(@as(T, 0)));
try std.testing.expectEqual(@Vector(2, T){ 1, 0 }, sign(@Vector(2, T){ 2, 0 }));
}
{
const T = f16;
try std.testing.expectEqual(@as(T, 1), sign(@as(T, 2)));
try std.testing.expectEqual(@as(T, -1), sign(@as(T, -2)));
try std.testing.expectEqual(@as(T, 0), sign(@as(T, 0)));
// TODO - uncomment once @intToFloat supports vectors
// try std.testing.expectEqual(@Vector(3, T){ 1, -1, 0 }, sign(@Vector(3, T){ 2, -2, 0 }));
}
{
const T = f32;
try std.testing.expectEqual(@as(T, 1), sign(@as(T, 2)));
try std.testing.expectEqual(@as(T, -1), sign(@as(T, -2)));
try std.testing.expectEqual(@as(T, 0), sign(@as(T, 0)));
// TODO - uncomment once @intToFloat supports vectors
// try std.testing.expectEqual(@Vector(3, T){ 1, -1, 0 }, sign(@Vector(3, T){ 2, -2, 0 }));
}
{
const T = f64;
try std.testing.expectEqual(@as(T, 1), sign(@as(T, 2)));
try std.testing.expectEqual(@as(T, -1), sign(@as(T, -2)));
try std.testing.expectEqual(@as(T, 0), sign(@as(T, 0)));
// TODO - uncomment once @intToFloat supports vectors
// try std.testing.expectEqual(@Vector(3, T){ 1, -1, 0 }, sign(@Vector(3, T){ 2, -2, 0 }));
}
// comptime_int
try std.testing.expectEqual(-1, sign(-10));
try std.testing.expectEqual(1, sign(10));
try std.testing.expectEqual(0, sign(0));
// comptime_float
try std.testing.expectEqual(-1.0, sign(-10.0));
try std.testing.expectEqual(1.0, sign(10.0));
try std.testing.expectEqual(0.0, sign(0.0));
}
test "sign" {
try testSign();
comptime try testSign();
}