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
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