That was my point... `foo` doesn’t have a `T: Numeric` version, therefore when
it calls `isNumeric` the compiler has to call the version that always return
false. `bar` is overloaded with both a `T` and a `T: Numeric` version, so there
the compiler can call the most appropriate version of `isNumeric`.
- Dave Sweeris
> On Oct 5, 2017, at 01:49, Alex Blewitt <alb...@apple.com> wrote:
>
> I think one of your 'foo' or 'bar' is missing a <T:Numeric>, as otherwise the
> functions are identical ...
>
> Alex
>
>> On 5 Oct 2017, at 09:23, David Sweeris via swift-users
>> <swift-users@swift.org> wrote:
>>
>>
>> On Oct 4, 2017, at 18:30, Kevin Lundberg via swift-users
>> <swift-users@swift.org> wrote:
>>
>>> Can you do something like this?
>>>
>>> func isNumber<T: Numeric>(_ value: T) -> Bool { return true }
>>>
>>> func isNumber<T>(_ value: T) -> Bool { return false }
>>>
>>> I don't recall whether or not swift will pick the right version of the
>>> function here, or whether this can even compile (mac isnt open at the
>>> moment), but if you can overload functions in this way then it might be
>>> much nicer than checking for lots of concrete types.
>>>
>>
>> It’ll compile, but you’ll get the wrong answer if it’s called from another
>> generic function that isn’t similarly overloaded for `T` vs `T: Numeric`.
>> I’m not at my computer right now, but IIRC, this is correct:
>>
>> func foo<T> (_ value:T) -> Bool {
>> return isNumber(value)
>> }
>> func bar<T> (_ value:T) -> Bool {
>> return isNumber(value)
>> }
>> func bar<T: Numeric> (_ value:T) -> Bool {
>> return isNumber(value)
>> }
>> isNumber(0) //true
>> isNumber(“”) //false
>> foo(0) //false
>> foo(“”) //false
>> bar(0) //true
>> bar(“”) //false
>>
>> - Dave Sweeris
>> _______________________________________________
>> swift-users mailing list
>> swift-users@swift.org
>> https://lists.swift.org/mailman/listinfo/swift-users
>
_______________________________________________
swift-users mailing list
swift-users@swift.org
https://lists.swift.org/mailman/listinfo/swift-users
