[Pythonmac-SIG] [ann] appscript 0.4.0 released

[has]

Michael Hudson wrote:

>  >>1) override the bitwise operators
>  >
>  >     items.test((its.size > 12) & (its.color == [0,0,0])) # items whose
>>      size > 12 and color = {0,0,0}
>
>This kind of thing is I'm not a big fan of operator overloading, in
>general.

Heh, I'm not a big fan of operators; know what you mean though. 
Reason I'm trying it here is that a conventional method call-based 
approach soon becomes unreadable when constructing an expression of 
any complexity; for example:

    items.test(its.size.greaterthan(12).AND(its.color.equals([0,0,0])))

versus:

    items.test(its.size > 12 and its.color == [0,0,0])



>  > and not:
>>
>  >     ref.test(its.size > 12 & its.color == [0,0,0])
>>
>>  which'll cause an error when Python tries to evaluate '12 & its.color'
>>  instead of '<object> & <object>'.
>
>Huh?

Python's evaluation order is to do the bitwise AND before the 
comparison tests, so it sees:

    its.size > 12 & its.color == [0,0,0]

as:

    its.size > (12 & its.color) == [0,0,0]

instead of:

    (its.size > 12) & (its.color == [0,0,0])

which is what I want it to do.


>  >     ref.test(
>>            (its.size > 12) & (its.color == [0,0,0])
>>      )
>>
>>      ref.test(
>>            (its.size > 12).AND(its.color == [0,0,0])
>>      )
>>
>  >     ref.test(
>>            AND(its.size > 12, its.color == [0,0,0])
>  >     )
>>
>
>I think I prefer something like 3), but admittedly, I haven't used
>that style for anything much...

Worth playing around with to see what feels best to you. e.g. The 
third form should work quite well for users when there's only a 
single logical test involved, but may not work so well for more 
complex expressions, eg:

      (its.size > 12 and its.color == [0,0,0]) or (its.length > 0 and 
its.characters[1] != 'X')   # ideal (true infix)

      OR(AND(its.size > 12, its.color == [0,0,0]), AND(its.length > 0, 
its.characters[1] != 'X'))   # pseudo-prefix

      (its.size > 12).AND(its.color == [0,0,0]).OR(its.length > 
0).AND(its.characters[1] != 'X')   # pseudo-infix


(Ech. Decisions, decisions... But hey; I'm just the bloke wot writes 
it, youse all are the ones what gotta use it.;)

Thanks,

has
-- 
http://freespace.virgin.net/hamish.sanderson/