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Re: Lexical scoping like a fox

by adrianh (Chancellor)
on Nov 19, 2002 at 14:41 UTC ( #214130=note: print w/ replies, xml ) Need Help??


in reply to Lexical scoping like a fox

The way that you have used the term "lexical scope" when talking about local doesn't match the common definition of the term. For example see lexical scope and dynamic scope in FOLDOC.

Lexical scope is a compile-time construct relating to a region of the source code. With the commonly accepted definitions things like this:

With that said, what local does do is change the value of an existing package global for the length of a given lexical scope. Once that scope is exits, the package global returns to its former value e.g

and

If you've managed to succesfully understand and take in the tutorial up to this point you can see that local changes the value of $foo for the length of the lexical scope, and that it reverts to its original value once the scope exits.

use "lexical scope" incorrectly. local affects dynamic scoping - and is completely orthogonal to lexical scope. Almost the essence of local is that it can affect a variable outside of it's lexical scope :-)

In your example:

sub foo { # begin lexical scope local $x = "in the lexical scope of foo()"; print "\$x in foo() is: ", (defined $x ? $x : "undefined"), $/; bar(); } # end lexical scope sub bar { print "\$x in bar() is: ", (defined $x ? $x : "undefined"), $/; }

bar() is outside foo()'s lexical scope - demonstrating that local affects code outside the lexical scope it exists in.

Apart from that, nice intro :-)


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Re: Re: Lexical scoping like a fox
by broquaint (Abbot) on Nov 19, 2002 at 15:57 UTC
    local affects dynamic scoping - and is completely orthogonal to lexical scope. Almost the essence of local is that it can affect a variable outside of it's lexical scope
    Indeed. Thank you muchly for pointing this out, will update the tutorial accordingly along with the other updates mentioned above.
    HTH

    _________
    broquaint

      A good effort bro. Needs more monkeys and I'd like to see some footnotes that mention obscure Japanese rhythm-action games. ;-)

        A very good, understandable tutorial certainly worth my reading time.

        But I totally reject any reference to Japanese rythym-action games as a pernicious influence. Although it does need more monkeys. Or have we already typed enough?

        xenchu


        The Needs of the World and my Talents run parallel to infinity.

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