implicitVars [Was: Re: Best Practices in Rev development]

[Alex Tweedly]

J. Landman Gay wrote:
> Richard Gaskin wrote:
>
>> So given the freedom of not using explicitVars while fleshing out 
>> algorithms, is it really a valuable thing and I'm just lazy?
>>
>
> For the record, I don't like explicitVars because:
<snip - some good reasons omitted>


In particular, I agree with J's comment about the bloating of scripts 
with extra lines that make it harder to see the wood for the trees. But 
I do want to retain the benefits that I see in detecting typos and 
similar errors.

So here is an initial proposal for something I'm thinking of as 
"implicitVars". Don't focus on the part where I'm lazy and describe it 
in implementation terms - focus on the intended 'experience' for the 
end-user (i.e. scripter).

When implicitVars is enabled, the script parser does the same task of 
detecting undeclared variables as it currently does for explicitVars. 
However, when such an undeclared variable is found, the parser checks 
the list of 'implicitly' declared variables for the current handler.

If the variable is in this set of 'implicit' variables, then there is 
naturally no error. If the variable is not in the 'implicit' set of 
variables, then an error dialog is presented to the user; the user can 
choose to respond by either

    - adding this variable to the list  (i.e. the implicit list)

or

    - exiting to the script editor (e.g. to declare it, or to fix a 
typo, or ....)


Each handler therefore must have stored with it a set of implicitly 
declared variables; this list of variable names does *not* appear in the 
script itself. (Maybe it is stored as a custom property of the 
script/handler, or something like that - therefore it could be viewed, 
and even modified by the user - or by the script editor or add-ons to 
the editor).


This gives the advantage of a short, clean, easy-to-read script while 
preserving the advantage of error detection. The need to respond to such 
a dialog once per local variable would be (at least for me) a small 
price to pay - and is certainly much lighter a burden than the need to 
add a declaration for each.


-- 

Alex Tweedly      mailto:alex at tweedly.net      www.tweedly.net