On Mon, Feb 26, 2024 at 7:25 PM Brien Colwell <xcolw...@gmail.com> wrote:
> Interesting. That seems to break the comparable spec.
>
> >> Pointer types are comparable. Two pointer values are equal if they
> point to the same variable or if both have value nil. Pointers to distinct
> zero-size variables may or may not be equal.
>
How do you think this is broken? Note that there are two distinct variables
involved (a and b). Pointers to distinct variables are allowed to be equal,
or not to be equal.
> >> it would be valid for `==` on pointers to zero-sized types to always
> evaluate to `true`,
>
> This would be more straightforward behavior.
>
>
>
> On Feb 26, 2024, at 9:24 AM, tapi...@gmail.com <tapir....@gmail.com>
> wrote:
>
> package main
>
> var a, b [0]int
> var p, q = &a, &b
>
> func main() {
> if (p == q) {
> p, q = &a, &b
> println(p == q) // false
> }
> }
>
> On Thursday, February 22, 2024 at 6:55:49 PM UTC+8 Brien Colwell wrote:
>
>> I'm confused by this output. It appears that the interface of two
>> different pointers to an empty struct are equal. In all other cases,
>> interface equality seems to be the pointer equality. What's going on in the
>> empty struct case?
>>
>> ```
>> package main
>>
>> import "fmt"
>>
>> type Foo struct {
>> }
>>
>> func (self *Foo) Hello() {
>> }
>>
>> type FooWithValue struct {
>> A int
>> }
>>
>> func (self *FooWithValue) Hello() {
>> }
>>
>> type Bar interface {
>> Hello()
>> }
>>
>> func main() {
>> a := &Foo{}
>> b := &Foo{}
>> fmt.Printf("%t\n", *a == *b)
>> fmt.Printf("%t\n", a == b)
>> fmt.Printf("%t\n", Bar(a) == Bar(b))
>>
>> c := &FooWithValue{A: 1}
>> d := &FooWithValue{A: 1}
>> fmt.Printf("%t\n", *c == *d)
>> fmt.Printf("%t\n", c == d)
>> fmt.Printf("%t\n", Bar(c) == Bar(d))
>> }
>> ```
>>
>> Prints (emphasis added on the strange case):
>>
>> ```
>> true
>> false
>> **true**
>> true
>> false
>> false
>> ```
>>
>>
>>
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