Jeremy,
Perhaps is[nul] ?
There were cases where stuffing a field with null or a single space rather
than delete a field, technically these should be different
- is[blank] = empty or one or more spaces
- is[nul] = empty or a zero length string
I recall the mention of a logical high values and low values but can't find
any references to them. I though they may be relevant to this.
Regards
Tony
On Wednesday, March 4, 2020 at 10:17:14 PM UTC+11, Jeremy Ruston wrote:
>
> So,
> One should be very cautious to use is[blank]!
>
>
> As Mark points out, the subtlety is that it checks for a zero length
> string, rather than checking for a missing result. I’m not sure “blank” was
> necessarily the best word to have chosen; we could always introduce an
> alias if there’s a clearer word for it.
>
> Best wishes
>
> Jeremy
>
>
> --Mohammad
>
> On Tuesday, March 3, 2020 at 7:00:37 PM UTC+3:30, Mark S. wrote:
>>
>> isblank operates on the output of the new *split* operator, which might
>> be "mytitle" "" "someothertitle" "" etc.
>>
>> So there has to be a "" to determine if it is blank.
>>
>> Most filter operators do not produce "". If something is "", it puts out
>> NO output -- not even ""
>>
>> The operator getindex[xx] produces NO output, and so there is nothing to
>> evaluate. You get the same result whether you don't use is[blank] .
>>
>> So the upshot is, that is[blank] is mostly useful in the context of the
>> split and splitreg operators.
>>
>> On Tuesday, March 3, 2020 at 6:05:18 AM UTC-8, Mohammad wrote:
>>>
>>>
>>> - In tiddlywiki.com create a new tiddler titled as *dataTid *and
>>> set its type as application/json with below contents
>>>
>>> {
>>> "xx": "",
>>> "yy": "hello"
>>> }
>>>
>>>
>>>
>>> - in another tiddler issue the below command
>>>
>>> <$list filter="[[dataTid]getindex[xx]is[blank]]" emptyMessage="the index
>>> is NOT blank">
>>> The index is BLANK
>>> </$list>
>>>
>>> You get the wrong result. Why is[blank] does not detect the blank value
>>> of xx?
>>>
>>>
>>> --Mohammad
>>>
>>
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