Hi Nikolay,
On Tue, Jan 9, 2018 at 12:58 PM, Nikolay Aleksandrovich Pavlov
<zyx....@gmail.com> wrote:
> 2018-01-09 18:59 GMT+03:00 Yegappan Lakshmanan <yegapp...@gmail.com>:
>> Hi Nikolay,
>>
>> On Mon, Jan 8, 2018 at 11:41 PM, Nikolay Aleksandrovich Pavlov
>> <zyx....@gmail.com> wrote:
>>> 2018-01-08 9:23 GMT+03:00 Yegappan Lakshmanan <yegapp...@gmail.com>:
>>>> Hi,
>>>>
>>>> Which value you can use as the default value for a job
>>>> type variable? I see that there is a test_null_job() function
>>>> that returns a null job value (but it is supposed to be used
>>>> only for testing). But I don't see any other way to initialize
>>>> a variable to a null job value. Am I missing something?
>>>
>>> There is no such a thing as “abstract default value” in VimL, no
>>> matter the type; to define something like this language would need to
>>> have either constructions in which case return values of those
>>> constructors called without arguments may be named “default value for
>>> the type” (e.g. `list()` in Python returning empty list without
>>> arguments) or be typed without support for uninitialized variables
>>> (probably, only in part of the language) in which case whatever they
>>> are initialized to when not explicitly initialized define “default
>>> value for the type” (e.g. in C99 with `*tv = (typval_T) { .v_type =
>>> VAR_STRING }` everything, but `v_type` in `tv` becomes zero; another
>>> example is LabVIEW with “use default if unwired” terminals defaulting
>>> to false/empty array/etc). All other defaults come from code authors,
>>> for what you need to describe a task.
>>>
>>> So describe a task.
>>>
>>
>> I am creating a plugin that runs a command asynchronously.
>> This plugin supports only one asynchronous command at a time.
>> If the async command is already running, the plugin will stop the
>> current job and start a new job.
>>
>> I am using a variable to keep track of the current job. During the
>> plugin startup or when the job exits, I need to set this variable
>> to an empty or a sane value. Before starting a new job, I need to
>> compare this variable against some default value to check whether
>> a job is already running or not. As a workaround I am currently using
>> another variable to keep track of whether the job is running or not.
>>
>> We can use the following default values for other variable types:
>> Sting: "", Number: 0, List: [], Dict: {}. I am looking for some thing
>> similar for the Job variable.
>
> They are by no means default values, these are *empty* values, nothing
> more (see `:h empty()`, this applies to number too)
>
How do we assign an empty value to a variable of Job type?
>
> And VimL is not typed, you *don’t* need what you are asking for:
> just initialize variable to zero and check with `if var is 0`, this will yield
> false if `var` happens to have type other then Number or value other
> then zero.
>
Yes. I can use "is" to check whether var is set to 0. But this looks like
a workaround. I was looking for a way to initialize the variable to
an empty Job value. I will go with the "is" check for now.
Thanks,
Yegappan
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