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Comment by rednb | Hacker News Reader

Wow, what a vicious footgun. I do a lot of work related to pricing, invoicing, exchange rates etc... where decimals do matter, so this kind of stresses me out. Thanks for the heads up.

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You shouldn’t cast from double to decimal anyway. Just use decimal throughout.

Fair enough, this is mostly what i do but since the runtime has been forgiving, i'll need to triple check that. I label all pure money fields as decimal, but am less confident for the ProductQuantity kind of fields. I typically use int for whole numbers but wouldn't be surprised if i used float occasionnally for quantities accepting decimals.

Yeah, while I do agree this change in behavior could be a major footgun for a few people, the vast majority of use cases for decimal should be unaffected. Decimal is usually used for business applications to the exclusion of double/float, not alongside them (the only doubles I've seen in my company's applications are just storing Lat/Long values for addresses, everything else uses decimal values).

Hell, on the rare occasion I've needed to use a decimal literal in code, I just use a decimal literal: don't do (decimal)0.1, just use 0.1m.

Exactly. If you want an actual decimal literal you should always write it as 1.2345m rather than converting it with the (decimal) prefix. The compiler refuses to accept a plain 1.2345 assigned to a decimal type so it’s not such a footgun as it may appear to some; though it might offer a better DX if the type of the literal was inferred from the thing you are trying to assign it to, that would no doubt have unintended consequences.

0.1 is not representable in binary floating point. The old behavior was adding magic that shouldn't be there.

Did they deprecate it, then?

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