[PYTHON MATRIX-SIG] More on Less Copying
Tue, 11 Mar 1997 19:53:06 +0100
> I don't know if his opinions have changed lately, but at the Livermore
> workshop, Guido expressed a definite willingness to consider += operators.
>From the archives...
> > How about providing assignment operators? Some time one has to
> > build a thing piece-meal and this sort of operators are very
> > handy. The semantics are clear:
> > <var> <op>= <expr> === <var> = <var> <op> <expr>
> > Example:
> > a = 'ba '
> > a *= 2 # a = 'ba ba'
> > a += 'black sheep' # a = 'ba ba black sheep'
> Agreed. Now that the parser can actually recognize two-character
> operators, adding these wouldn't be so hard (except that the grammar
> tables will grow again :-( ).
> > I would also like the capability of overloading standard operators
> > for predefined and user defined classes. Thus instead of
> > result.append(b)
> > I should be able to say
> > result += b
> > or better still,
> > result += [a,b,c]
> The latter should automatically work if we let x += y be syntactic
> sugar for x = x+y. Note that result = result + [x] has a different
> meaning than result.append(x), although in many cases it doesn't
> matter: result.append(x) modifies the existing object that result is
> bound to, while result = result+[x] creates a new list (the
> concatenation of result and [x]) and binds result to it, forgetting
> the object to which result was bound previously. If there was another
> reference to that object, e.g., through an assignment "z = result"
> earlier on, the value of z is unchanged by the second form, but
> modified by the first form. Confusing? Yes, but this is a lot better
> than allowing arbitrary pointers!
We're still waiting ;-)
Cheers /F (http://hem1.passagen.se/eff)
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