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- Subject: Re: Lexical scope definition
- From: Edgar Toernig <froese@...>
- Date: Fri, 31 Aug 2001 04:24:40 +0200
"John D. Ramsdell" wrote:
> "Jonathan Branam" <firstname.lastname@example.org> writes:
> > http://ase.isu.edu/ase01_07/ase01_07/bookcase/ref_sh/foldoc/14/62.htm
> > lexical scope
> > <programming> (Or "static scope") In a lexically scoped language, the scope
> > of an identifier is fixed at compile-time to be the smallest block
> > (begin/end or function/procedure body) containing the identifier's
> > declaration. This means that an identifier declared in some block is only
> > accessible within that block and from procedures declared within it.
> > Opposite of dynamic scope. See activation record.
> Thank you for finding many references that support my notion of
> lexical scoping. Thank you also for finding the particular definition
> I was looking for. Notice that by this definition, Lua is not
> statically scoped.
First, this definition makes no distinction between lexical and static
Then, this definition takes more constraints on the lexical scope then
most other definitions - it makes the "most closely nested" rule a
requirement. It excludes all languages that do not use this rule.
What are these languages? Neither dynamic nor lexical or static. Not
scoped at all?!?
Further: It says "...only accessible within that block and from procedures
within it." Maybe it would be better to say "visible" than "accessible".
And in Lua variables are visible from nested functions - only the access
to them is forbidden.
And last: this is from "The Free On-Line Dictionary of Computing" compiled
by hundreds of contributors. It's hardly a normative reference; especially
this entry has more the nature of a glossary entry. I guess, if I would
made a more formal chapter about lexical scoping it would be added. ;-)
 the wording is a little bit vague anyway: it would not allow nested
blocks to access a variable. Lua would not even have blocks because
they are not made with "begin/end". ;-) And functions are not allowed
either, only procedures...