On Thursday, September 29, 2016 at 12:56:57 PM UTC+8, Micky wrote:
>
> The reason is directly stated in the Go language spec:
>
> "If the type assertion holds, the value of the expression is the value
> stored in x and its type is T. If the type assertion is false, a run-time
> panic <https://golang.org/ref/spec#Run_time_panics> occurs."
>
> Here "hold" means if it succeeds.
>
>
I know of the syntax in spec.
I just want to understand what is the deep reason for the syntax
inconsistency between map index and type assert.
>
> On Thu, Sep 29, 2016 at 9:53 AM, T L <tapi...@gmail.com <javascript:>>
> wrote:
>
>>
>>
>> On Thursday, September 29, 2016 at 12:32:48 PM UTC+8, Henrik Johansson
>> wrote:
>>>
>>> This is just how type assertion works.
>>> If you don't use the dual return it panics if the actual type is
>>> different from the one you try to assert.
>>>
>>
>> but what is the underlining reason for the inconsistency between map
>> index and type assert?
>>
>>
>>>
>>> On Thu, Sep 29, 2016, 05:26 T L <tapi...@gmail.com> wrote:
>>>
>>>> package main
>>>>
>>>> func main() {
>>>> var m = map[string]int{}
>>>> _, _ = m["abc"] // ok
>>>> _ = m["abc"] // ok
>>>>
>>>> var i interface{} = 789
>>>> _, _ = i.(bool) // ok
>>>> _ = i.(bool) // panic: interface conversion: interface is int, not
>>>> bool
>>>> }
>>>>
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>
>
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