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std: stop relying on precision-losing coercions

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mlugg 2025-07-31 10:56:49 +01:00
parent e664bf4d81
commit 64bf8bb146
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GPG key ID: 3F5B7DCCBF4AF02E
5 changed files with 29 additions and 25 deletions
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10
lib/std/math.zig
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@ -1345,11 +1345,15 @@ pub fn lossyCast(comptime T: type, value: anytype) T {
}
},
.float, .comptime_float => {
// In extreme cases, we probably need a language enhancement to be able to
// specify a rounding mode here to prevent `@intFromFloat` panics.
const max: @TypeOf(value) = @floatFromInt(maxInt(T));
const min: @TypeOf(value) = @floatFromInt(minInt(T));
if (isNan(value)) {
return 0;
} else if (value >= maxInt(T)) {
} else if (value >= max) {
return maxInt(T);
} else if (value <= minInt(T)) {
} else if (value <= min) {
return minInt(T);
} else {
return @intFromFloat(value);
@ -1366,7 +1370,7 @@ test lossyCast {
try testing.expect(lossyCast(i16, 70000.0) == @as(i16, 32767));
try testing.expect(lossyCast(u32, @as(i16, -255)) == @as(u32, 0));
try testing.expect(lossyCast(i9, @as(u32, 200)) == @as(i9, 200));
try testing.expect(lossyCast(u32, @as(f32, maxInt(u32))) == maxInt(u32));
try testing.expect(lossyCast(u32, @as(f32, @floatFromInt(maxInt(u32)))) == maxInt(u32));
try testing.expect(lossyCast(u32, nan(f32)) == 0);
}

32
lib/std/math/gamma.zig
View file

@ -189,19 +189,19 @@ fn series(comptime T: type, abs: T) T {
2.5066282746310002701649081771338373386264310793408,
};
const denominator = [_]T{
0,
39916800,
120543840,
150917976,
105258076,
45995730,
13339535,
2637558,
357423,
32670,
1925,
66,
1,
0.0,
39916800.0,
120543840.0,
150917976.0,
105258076.0,
45995730.0,
13339535.0,
2637558.0,
357423.0,
32670.0,
1925.0,
66.0,
1.0,
};
var num: T = 0;
var den: T = 0;
@ -244,9 +244,9 @@ const expectApproxEqRel = std.testing.expectApproxEqRel;
test gamma {
inline for (&.{ f32, f64 }) |T| {
const eps = @sqrt(std.math.floatEps(T));
try expectApproxEqRel(@as(T, 120), gamma(T, 6), eps);
try expectApproxEqRel(@as(T, 362880), gamma(T, 10), eps);
try expectApproxEqRel(@as(T, 6402373705728000), gamma(T, 19), eps);
try expectApproxEqRel(@as(T, 120.0), gamma(T, 6), eps);
try expectApproxEqRel(@as(T, 362880.0), gamma(T, 10), eps);
try expectApproxEqRel(@as(T, 6402373705728000.0), gamma(T, 19), eps);
try expectApproxEqRel(@as(T, 332.7590766955334570), gamma(T, 0.003), eps);
try expectApproxEqRel(@as(T, 1.377260301981044573), gamma(T, 0.654), eps);

2
lib/std/math/modf.zig
View file

@ -74,7 +74,7 @@ fn ModfTests(comptime T: type) type {
r = modf(@as(T, 43874.3));
try expectEqual(43874.0, r.ipart);
// account for precision error
const expected_b: T = 43874.3 - @as(T, 43874);
const expected_b: T = 43874.3 - @as(T, 43874.0);
try expectApproxEqAbs(expected_b, r.fpart, epsilon);
r = modf(@as(T, 1234.340780));

4
lib/std/math/pow.zig
View file

@ -192,8 +192,8 @@ fn isOddInteger(x: f64) bool {
}
test isOddInteger {
try expect(isOddInteger(math.maxInt(i64) * 2) == false);
try expect(isOddInteger(math.maxInt(i64) * 2 + 1) == false);
try expect(isOddInteger(@floatFromInt(math.maxInt(i64) * 2)) == false);
try expect(isOddInteger(@floatFromInt(math.maxInt(i64) * 2 + 1)) == false);
try expect(isOddInteger(1 << 53) == false);
try expect(isOddInteger(12.0) == false);
try expect(isOddInteger(15.0) == true);

6
lib/std/zon/parse.zig
View file

@ -2774,11 +2774,11 @@ test "std.zon parse float" {
// Test big integers
try std.testing.expectEqual(
@as(f32, 36893488147419103231),
@as(f32, 36893488147419103231.0),
try fromSlice(f32, gpa, "36893488147419103231", null, .{}),
);
try std.testing.expectEqual(
@as(f32, -36893488147419103231),
@as(f32, -36893488147419103231.0),
try fromSlice(f32, gpa, "-36893488147419103231", null, .{}),
);
try std.testing.expectEqual(@as(f128, 0x1ffffffffffffffff), try fromSlice(
@ -2788,7 +2788,7 @@ test "std.zon parse float" {
null,
.{},
));
try std.testing.expectEqual(@as(f32, 0x1ffffffffffffffff), try fromSlice(
try std.testing.expectEqual(@as(f32, @floatFromInt(0x1ffffffffffffffff)), try fromSlice(
f32,
gpa,
"0x1ffffffffffffffff",