On Thu, Oct 13, 2016 at 8:36 AM, <d...@veryhaha.com> wrote:
>
> On Thursday, October 13, 2016 at 11:24:50 PM UTC+8, Jesper Louis Andersen
> wrote:
>>
>> The rule is that a short variable declaration requires that at least one
>> non-blank variable is new (the specification even says so) Consider
>>
>> _, y := 4,5
>>
>> where one variable, y, is new. In
>>
>> _ := 6
>>
>> or
>>
>> _, _ := 5, 7
>>
>> this rule is violated, since there are no non-blank variables (and thus
>> vacuously nothing new).
>>
>> I think the reason this is a rule is because it may detect some spurious
>> errors by forcing the programmer to write code in a certain style, but I may
>> be wrong.
>
>
>
> What spurious errors?
The error of thinking that because you are using := you are getting a
new variable.
The handling of := is a bit tricky, perhaps too tricky. It used to
always declare new variables, and give an error if there was already a
variable of the same name in the same scope. But that was too painful
to use with the err variable, because of the common use of
n, err := F()
So := was changed to permit reusing a variable if it already existed
in the same scope with the same name and (inferred) type.
Ian
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