[Zope-dev] local/set

[Evan Simpson]

"Phillip J. Eby" wrote:

> Let me throw out a counter-proposal, however.  Suppose that the
> _()/_.namespace() functions were changed to return writable namespace
> objects?

I confess to having already done this for my own use since v1.10.2

Your point about untrusted-call safety is well-taken, and now that I think about
it I have an alternate proposal :-)

If only lexically enclosed code is allowed to alter Let variables, why even
bother with non-writable variables?  Allow Set to operate on the enclosing Let
namespace, without limit.  Heck, allow it to introduce new names, if it wants to.

Thus:

<dtml-let x="1+1" firstname=" 'fred' ">
  ...
  <dtml-set firstname=" 'mary' " weight="135">
  ...
  <dtml-set qty="5" price="1.50" extprice="qty * price">
  ...
</dtml-let>

Note that this makes nested Let superfluous, and <dtml-let ...> is essentially
shorthand for <dtml-let><dtml-set ...>

Now if every DTML object had a default empty local namespace, we could do away
with Let entirely and just use Set.

> Then, your example could be written as:
>
> <dtml-let x="1+1" person="_(firstname='fred',weight=180)">
>  <dtml-var x>, <dtml-var "person.firstname">, <dtml-var "person.weight">
>  <dtml-call "person.set('weight',185)">
>  <dtml-var weight>

This diverges here, since 'weight' is *only* an attribute of 'person', not a full
member of the namespace.  Of course, to complete the insanity of my new proposal,
we could keep the colon notation as a compact way of defining/altering this sort
of sub-namespace 8->

> Last, but not least, I should probably note that my enthusiasm at the
> simplicity and elegance of these solutions from a programming standpoint is
> matched only by my misgivings about how much harder they may be to teach
> someone how to use than local/set.  But I guess I'll withhold judgment on
> that until I've had to do it.  :)

Ditto.

Cheers,

Evan @ 4-am