[stringtemplate-interest] null vs missing vs empty vs nonexistent

[Graham Wideman]

At 10/15/2009 01:56 PM, Terence Parr wrote:
>was thinking about that but figured it'd confuse. we have <if(!foo)foo  
>is missing<endif> anyway.

...though ! appears to have two problems for detecting the missing case: it doesn't distinguish between FALSE and null (and missing if missing is legal here), and docs I think probably aren't clear on whether the missing case is legal and treated like null, or should cause error.

Generally I think if you establish missing as a concept distinct from null, then to minimizing confusion means that everywhere those concepts arise they should get distinct treatment (eg: parallel options in render).

This of course runs into trouble applying boolean operators to what is now becoming a 4-value situation: true-val/false-val/null/missing --> true/false/maybe-error.

:-(

No time as good as a new version to take a stand though!

(BTW, are you really saying there are also empty and nonexistant cases?)

Graham


>Ter
>On Oct 15, 2009, at 1:53 PM, Graham Wideman wrote:
>
>> If you're worried about whether the missing case should or should  
>> not be treated like null, might you consider a missing="something"  
>> option to parallel null="something"?
>>
>> -- Graham
>>
>> At 10/15/2009 12:25 PM, you wrote:
>>> Ok, we have an important choice to make. Thanks to Bill Venners were
>>> bringing this up last year. It's important enough and long enough  
>>> that
>>> I added to my blog:
>>>
>>> http://tinyurl.com/parrt-on-null-attributes
>>>
>>> Here is my summary from the bottom of the page:
>>
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