PEP 318 - Function Modifier Syntax

[Beni Cherniavsky]

Duncan Booth wrote on 2003-06-09:

> You need to say what order the modifiers are applied when there is
> more than one. Specifically is it left to right, or right to left?
>
> I wonder what the implementation of this should be. Should the
> bytecode that is produced implement a loop over the modifiers
> directly, or should there be a new builtin that takes the function
> and the modifiers as arguments and the bytecode simply has to call
> the function and assign its result to the name? The second of these
> sounds as though it ought to be simpler to implement.
>
In the latter case you don't need new builtins at all.  Just
compile::

    def spam() [foo, bar]:
        pass

exactly as::

    def spam():
        pass
    spam = foo(spam)
    spam = bar(spam)

The limitation for avoiding a loop is that the individual expressions
of the items should be known when compiling.  You can always allow the
generic case with a loop and consider this purely an optimization.

I wrote the last lines this way rather than::

    spam = bar(foo(spam))

to emphasize the order.  IMO since they are written at the end of the
line, the only sensible order is applying them left-to-right.  This is
like postfix (reverse polish) notation: the outermost application is
written last.

-- 
Beni Cherniavsky <cben at users.sf.net>