Thanks, my question is about this line in your expanded plus function:
res := aInt + bInt // type: myInt
It's not clear to me why *aInt + bInt* results in a type myInt. I thought
that the plus operator would return an int, not a myInt.
On Sunday, February 18, 2018 at 3:00:00 AM UTC-5, Krzysztof Kowalczyk wrote:
>
> 2 things:
>
> 1. plus() returns interface{}.
>
> "%T" prints underlying dynamic type of interface{} value, but static type
> of returned value of plus is interface{}
>
> You can assign any type to interface{} without a cast by definition (see
> e.g.
> https://www.programming-books.io/essential/go/a-90100072-empty-interface)
>
> What it means is this is valid in Go:
>
> var v interface{}
> v = 5 // no cast needed
> v = "foo" // no cast needed
>
> interface{} is Go's version of dynamic type. It wraps any type as a tuple
> (type, value).
>
> 2. Let's expand plus() function:
>
> func plus(a, b interface{}) interface{} {
> aInt := a.(myInt) // type: myInt
> bInt := b.(myInt) // type: myInt
> res := aInt + bInt // type: myInt
> var ires interface{} = res; // no cast needed, see above
> return ires
> }
>
> Hope this clarifies the typing.
>
> Aside: if you come from C++, aliasing interface{} as any might feel
> comfortable, but that's not a good Go style.
>
>
> On Saturday, February 17, 2018 at 9:03:58 PM UTC-8, Bill Wood wrote:
>>
>> HI, Go newbie here... not sure if this is a dumb question or not :)
>>
>> I have a simple program:
>>
>> package main
>>
>> import "fmt"
>>
>> type any interface{}
>> type myInt int
>>
>> func plus(a, b any) any { return a.(myInt) + b.(myInt) }
>>
>> func main() {
>> s := plus(myInt(3), myInt(2))
>> fmt.Printf("%v, %T\n", s, s)
>> }
>>
>>
>> Output:
>>
>> 5, main.myInt
>>
>>
>> Why does func plus return a myInt? Why isn't a cast needed, ie:
>>
>> func plus(a, b any) any { return myInt(a.(myInt) + b.(myInt)) }
>>
>>
>> Thanks!
>>
>
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