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Re: Add nested-function support in a language the based on a stack-machine

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On 2018-03-01, Kaz Kylheku <217-679-0842@kylheku.com> wrote:
> John:
> [A display is an array of pointers to the frames of the enclosing
> scopes.  You can access any variable in an enclosing frame by
> indirecting through the frame's entry in the current display and then
> indexing.  This is for languges like Algol and Pascal, not Lisp.  I

This is absolutely relevant to Lisp dialects with lexical scoping,
like Common Lisp and Scheme (or anything worth its salt, really).
There are no first-class functions without lexical scoping.

Structure and Interpretation of Computer Programs (SICP) discusses
something similar to displays in "5.5.6 Lexical Addressing":

https://mitpress.mit.edu/sicp/full-text/book/book-Z-H-35.html#%_sec_5.5.6

"We can exploit this fact by inventing a new kind of variable-lookup
operation, lexical-address-lookup, that takes as arguments an
environment and a lexical address that consists of two numbers: a frame
number, which specifies how many frames to pass over, and a displacement
number, which specifies how many variables to pass over in that frame.
Lexical-address-lookup will produce the value of the variable stored at
that lexical address relative to the current environment."

The focus of that section is eliminating the run-time search which
actually finds a name by symbol matching, with numeric indexing.
However, if we can "pass over" the frames by indexing through a vector
of them, then we have a display. We can also directly index into the
frame by also representing it as a vector, so we don't have to
"pass over" n-1 variables to get to the n-th one.

[I was thinking of closures when I said not Lisp.  I suppose you could
use displays and garbage collect them but I haven't really thought
about the implications. -John]

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Add nested-function support in a language the based on a stack-machine dror.openu@gmail.com - 2018-02-12 11:25 -0800
  Re: Add nested-function support in a language the based on a stack-machine dror.openu@gmail.com - 2018-02-12 14:16 -0800
    Re: Add nested-function support in a language the based on a stack-machine Hans-Peter Diettrich <DrDiettrich1@netscape.net> - 2018-02-13 12:10 +0100
  Re: Add nested-function support in a language the based on a stack-machine Louis Krupp <lkrupp@nospam.pssw.com.invalid> - 2018-02-13 00:42 -0700
    Re: Add nested-function support in a language the based on a stack-machine Kaz Kylheku <217-679-0842@kylheku.com> - 2018-02-14 00:59 +0000
      Re: Add nested-function support in a language the based on a stack-machine George Neuner <gneuner2@comcast.net> - 2018-02-13 22:04 -0500
        Re: Add nested-function support in a language the based on a stack-machine Kaz Kylheku <217-679-0842@kylheku.com> - 2018-02-14 18:06 +0000
          Re: Add nested-function support in a language the based on a stack-machine George Neuner <gneuner2@comcast.net> - 2018-02-15 11:41 -0500
            Re: Add nested-function support in a language the based on a stack-machine Kaz Kylheku <217-679-0842@kylheku.com> - 2018-02-17 16:13 +0000
              Re: Add nested-function support in a language the based on a stack-machine anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2018-02-17 16:39 +0000
                Re: Add nested-function support in a language the based on a stack-machine George Neuner <gneuner2@comcast.net> - 2018-03-01 13:48 -0500
                Re: Add nested-function support in a language the based on a stack-machine Kaz Kylheku <217-679-0842@kylheku.com> - 2018-03-01 19:26 +0000
                Re: Add nested-function support in a language the based on a stack-machine Kaz Kylheku <217-679-0842@kylheku.com> - 2018-03-02 00:38 +0000
                Re: Add nested-function support in a language the based on a stack-machine George Neuner <gneuner2@comcast.net> - 2018-03-02 02:48 -0500
                Re: Add nested-function support in a language the based on a stack-machine rpw3@rpw3.org (Rob Warnock) - 2018-03-03 16:00 +0000
                Re: Add nested-function support in a language the based on a stack-machine anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2018-03-02 09:30 +0000
                Re: Add nested-function support in a language the based on a stack-machine anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2018-03-05 15:01 +0000
                Re: Add nested-function support in a language the based on a stack-machine George Neuner <gneuner2@comcast.net> - 2018-03-05 15:51 -0500
                Re: Add nested-function support in a language the based on a stack-machine George Neuner <gneuner2@comcast.net> - 2018-03-05 14:39 -0500
                Re: Add nested-function support in a language the based on a stack-machine John Levine <johnl@taugh.com> - 2018-03-06 04:31 +0000
                Re: Add nested-function support in a language the based on a stack-machine Kaz Kylheku <217-679-0842@kylheku.com> - 2018-03-06 18:17 +0000
                Re: Add nested-function support in a language the based on a stack-machine Kaz Kylheku <157-073-9834@kylheku.com> - 2018-03-11 03:19 +0000
                Re: Add nested-function support in a language the based on a stack-machine Tomasz Kowaltowski <tk@ic.unicamp.br> - 2018-03-06 12:10 -0300
                Re: Add nested-function support in a language the based on a stack-machine bartc <bc@freeuk.com> - 2018-03-06 19:02 +0000
                Re: Add nested-function support in a language the based on a stack-machine antispam@math.uni.wroc.pl - 2018-04-29 16:29 +0000
              Re: Add nested-function support in a language the based on a stack-machine George Neuner <gneuner2@comcast.net> - 2018-03-01 13:49 -0500
    Re: Add nested-function support in a language the based on a stack-machine George Neuner <gneuner2@comcast.net> - 2018-02-13 22:37 -0500
  Re: Add nested-function support in a language the based on a stack-machine George Neuner <gneuner2@comcast.net> - 2018-02-13 23:27 -0500
  Re: Add nested-function support in a language the based on a stack-machine Shoefoot <shoefoot@gmail.com> - 2018-02-14 12:27 -0800

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