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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
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);
}