Why? Zero is the additive identity. It's only bad if you want to denote a value that contains zeros that doesn't support addition, but that's only bad because of a misconception that Zero should mean "a default value" when we have Default for that. For reference, the Zero trait lives in std::num, which should be a good indication that this is a property of numeric types.
AdditiveIdentity is the only reasonable alternative, but that's a mouthful of a name and I think changing the name to this would be more confusing. Someone who needs a numeric zero isn't going to go looking for AdditiveIdentity, they're going to look for Zero. -Kevin On Apr 9, 2014, at 6:29 AM, Liigo Zhuang <[email protected]> wrote: > Zero is a bad name here, it should be renamed or removed > > 2014年4月9日 上午1:20于 "Kevin Ballard" <[email protected]>写道： > On Apr 7, 2014, at 1:02 AM, Tommi Tissari <[email protected]> wrote: > >> On 07 Apr 2014, at 08:44, Nicholas Radford <[email protected]> wrote: >> >>> I think the original question was, why does the zero trait require the add >>> trait. >>> >> If that was the original question, then my answer would be that >> std::num::Zero requires the Add trait because of the way it is specified: >> "Defines an additive identity element for Self". Then the question becomes: >> "why is Zero specified like that?", and I would answer: because then you can >> use it in generic algorithms which require their argument(s) to have an >> additional identity. > > If you want a zero value for a type that doesn't support addition, > std::default::Default may be a good choice to use. Semantically, that > actually returns the "default value" for a type instead of the "zero value", > but in a type without addition, how do you define "zero value"? > > -Kevin > > _______________________________________________ > Rust-dev mailing list > [email protected] > https://mail.mozilla.org/listinfo/rust-dev >
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