[Python-Dev] ANN: PEP 335: Overloadable Boolean Operators

[Kevin Jacobs]

exarkun at divmod.com wrote:

>On Tue, 14 Sep 2004 08:04:45 -0400, Kevin Jacobs <jacobs at theopalgroup.com> wrote:
>  
>
>>Phillip J. Eby wrote:
>>    
>>
>>>For these reasons, I'd feel more comfortable with either a literal 
>>>syntax (to address algebra, SQL, etc.) or some type of special infix 
>>>notation to allow new operators to be defined in Python, so that it 
>>>isn't necessary to use prefix or method notation to perform operations 
>>>like these.  Neither of these solutions burdens applications that 
>>>don't need the feature(s).
>>>      
>>>
>>Both of your alternatives are being used in some form and
>>neither is really satisfactory.  Literal representations require
>>complex parsers, when the Python parser is really what is
>>desired.
>>    
>>
>  Python's parser is already available, through the compiler module.  The example given earlier, query("x and y or z"), is relatively straightforward to implement as a set of AST manipulations.
>  
>

While strictly true, your suggestion still requires two
distinct parsers (although one implementation) and
two distinct parsing contexts (one embedded in a literal
string). 

The use cases I care about involve minimizing the difference
between evaluating regular Python expressions and
ADT instances -- plus the ability to mix constructs from both
in a seamless way.  If Python didn't support any over-loadable
ADT methods, then this wouldn't be an issue.  However,
the problem is that virtually all ADT methods _are_ defined
_except_ logical conjunction and disjunction.  Thus, I am
more concerned with correcting this oversight than I am with
a fraction of a percent in slowdown in real applications.
(or at least micro-benchmarks are _not_ representative
of any real world situations I've ever cared about)

-Kevin