Re: Force a value:pair assignment to be string?

Ingy dot Net wrote:
> On 17/04/07 17:40 -0400, Clark C. Evans wrote:
>   
>> Kenneth,
>>
>> short answer:
>>   You should be able quote those Y/N items to force them 
>>   to be a string.
>>
>> long answer:
>>   You might be able to configure your parser to not "implicitly
>>   type" Y/N as a boolean value.  
>>
>> longest answer: >
>>   You've hit the #1 usability prooblem with YAML, it's called "implicit
>>   type resolution" and different implementations are doing it
>>   differently.  
>>   
>>   The original goal was to make it easy to type in integers and have
>>   them show up as integers w/o littering your text with "!!int".
>>   Unfortuntely, where that line should be drawn is a bit hard.
>>
>>   In the next pass of YAML, I am going to recommend that all parsers
>>   _only_ do implicit typing on:
>>   
>>     (a) symbolic values, such as <<, which can be used to 
>>         augment the YAML syntax /w very nice hooks
>>         
>>     (b) numbers, "true" "false" and "null", following
>>         the JSON standard (for compatibility)
>>
>>   At least, this should, IMHO, be the default.  I think Ingy begs
>>   to differ and believes the default should be *all strings* with
>>   no implicit typing.  What ever we come up with, getting there 
>>   is sure to be unpleasent; but probably far less unpleasant than
>>   the current state of affairs.
>>     
>
> I disagree but in specifics, not in spirit. The "Parser" should not do typing
> of any form. It reports for each scalar, a char-string value, and whether the
> scalar was plain or not.
>
> A yaml "Load" operation consists of at least 3 steps, "parse", "compose",
> "construct". According to the spec, introduction of node "tag" (aka "type")
> happens in the composer.
>
> Whatever...
>
> Your point is that we got too cute with the default implicit types. String,
> Integer and Number are fine as a default.
>
> I would reccomend that all implementations support a everything is string mode. 
>   

I would ask, what is simplest and most consistent.  And also, how did 
the conversation start?

The conversation started because these two elements (is that the right 
word?) give different results:

item:
  prop_1st: value    # yields the string "value"
  prop_2nd: Y         # yields a numeric 1!  Newbie says huh??

What options are available?

1) Tweak default behavior.  Pro: Might satisfy this case.  Con: Might 
break older files, or require them to be version-stamped.  Con: Will 
just be an invitation to more tweaking and nobody will ever be happy.  
Con: will create a list of incompatible versions with incomprehensible 
variations (this is the end-result of taking this road).  Think HTML 3, 
html 3 for ie, html 4, html 4 for ie, html 4 for mozilla pre 6, mozilla 
6, etc etc etc.

2) Support for header directives for the possible options.  Possible 
directives:

none: follow behavior from before directives became available, so my Y 
above becomes a 1

"booltrue: Y, 1, Yes, YES", some kind of explicit list of values that 
will be treated as boolean true.  If my Y is not listed it wont be 
treated as a boolean.

boolfalse: same as booltrue, list of false values

date: xx-xx-xxxx,  anything that fits the picture is treated as a date.

numdigits: Treat any string composed only of numerals as a number

...others as they come to mind.  Those are off the top of my head, a 
real effort would have to be made to seek the list of directives that 
served all purposes without overlap or missing possibilities.

3) Declaring types for named properties. In the above example I would 
declare in the header that "prop_2nd" is a string.

4) Type-casting at the definition, which I believe is supported now with 
"tags".

If Ken were calling the shots, option 1 would be thrown out, option 4 is 
already supported, so supporting options 2 and 3 would produce the 
general solution, and then it becomes a matter of programmer preference 
and then you wait for best practices to emerge through community use of 
the various approaches.



-- 
Kenneth Downs
Secure Data Software, Inc.
www.secdat.com    www.andromeda-project.org
631-379-7200   Fax: 631-689-0527

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