why cannot assign to function call
castironpi at gmail.com
Sat Jan 10 12:30:55 CET 2009
On Jan 9, 9:30 am, Joe Strout <j... at strout.net> wrote:
> Aaron Brady wrote:
> > Possible compromise. You can think of functions as mutation-only.
> > You pass the object, and it gets a new (additional) name. The old
> > name doesn't go in. </compromise>
> That's correct. The reference itself is passed in, not the variable (or
> expression) that held or generated the reference in the calling code.
This is very odd, and I see it quite a bit.
Me: "You pass the object."
Joe: "That's correct. You pass the reference."
What was wrong with my original?
> This is true. (Technically, instead of variable, we should say "LValue"
> here -- there are things slightly more complex than simple variables
> that can serve as the left-hand side of an assignment. So replace
> "variable" with "lvalue" above if you prefer.)
This is a point worth making. I want to penny-pinch every term in an
introductory text, though, so, it's a tough call.
> M2: If 'fun()' returned a reference, you might be able to mutate the
> object that refers to.
> m2: You can sometimes mutate the object it refers to.
> C2: 'fun()' returns a reference.
This is horrendous.
A question: Are you Joe and you Mark certain that the simplest
possible introductory explanation makes use of the term 'reference'?
Perhaps we can have a contest for shortest/simplest/best description
of Python's data/variable/argument model.
Lastly, I don't see any reason why we couldn't make both explanations
available. 'For those coming from Java/etc....; for those coming from
C++/etc.....' They would both get read.
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