what's so difficult about namespace?

[Xah Lee]

Xah Lee wrote:
> i cannot fathom what could possibly be difficult of
> introducing or implementing a namespace mechanism into a language.

Joshua Cranmer wrote:
>> Namespaces go to the very core of a language, name resolution.
>> Retroactively adding such a feature is extremely difficult because there
>> is a strong chance of accidentally breaking existing code.

Xah Lee wrote:
> > could you give some technical detail on this?
>
> > i don't know compiler so am probably being foolish here... but i
> > suppose ultimately name resolution and storage at heart is something
> > like a hashtable...  namely,
>
> > put ‹identifier 1› table
> > put ‹identifier 2› table
>
> > and lookup is just
>
> > retrieve ‹identifier› table
>
> > and now suppose we introduced namespace, so i imagine the compiler
> > simply just concat namespace component befor put, and split before
> > retrieve?

Steve Holden wrote:
> And therein lies the danger of imagination.

> Typically the namespace components are looked up one by one, so for
>
>    this.that.theother
>
> first "this" will be looked up and (hopefully) yield an object with a
> namespace, which will then be searched for "that", yielding another
> object with a namespace in which "theother" can be looked up. That's
> certainly how it works in Python:

yes, but Steve, what is your point?

The question is, what is the technical difficulty, if any, of
introducing namespace into a existing language.

You pointed out that identifier lookup at least from the perspective
of language user is somewhat like a tree walking processing. However,
that does not answer the main question.

  Xah
∑ http://xahlee.org/

☄