(re-adding the list)
On Mon, Sep 10, 2012 at 5:20 PM, Tobie Langel <[email protected]> wrote:
> Yes, sorry for being unclear. What I meant to say was that I would
> expect EXPR1 and EXPR2 to have been evaluated within the lexical scope
> of f() at the time of function declaration, in source order, so:
That is how it works in Python, and it's astonishing when the
default-expression produces something mutable:
def getNames(target=[]):
target.append('kaitlin')
return target
getNames() # returns ['kaitlin']
getNames() # returns the same list, which now contains
['kaitlin', 'kaitlin']
It also means that later arguments' default-expressions can't use
earlier arguments' values, because at the time the default-expression
is evaluated, those arguments don't have values yet.
C++ evaluates the default-expression each time the value is needed.
This seems more sensible to me and it's what has been specified (and
implemented in SM) for ES6.
> var FOO = 2;
>
> function f(y = FOO + 3) {
> return y;
> }
>
> f();
>>>> 5
> FOO = 45;
>>>> 45
> f();
>>>> 5
This example doesn't bring up any scoping issues, though. It only
brings up timing issues. I think those are pretty well settled.
-j
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