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Groups > comp.lang.forth > #41004
| From | "Alex McDonald" <blog@rivadpm.com> |
|---|---|
| Newsgroups | comp.lang.forth |
| Subject | Re: RfD: Quotations |
| Date | 2015-07-31 10:53 +0100 |
| Organization | A noiseless patient Spider |
| Message-ID | <mpfggi$9m4$1@dont-email.me> (permalink) |
| References | (7 earlier) <mpbo6b$bkf$1@newsreader4.netcologne.de> <mpcm2n$gnf$1@dont-email.me> <mpcsv0$1hu$1@newsreader4.netcologne.de> <mpcto9$bkg$1@dont-email.me> <mpd3la$6fk$1@newsreader4.netcologne.de> |
on 30/07/2015 13:00:46, Bernd Linsel wrote:
> Am 30.07.2015 um 12:21 schrieb Alex McDonald:> on 30/07/2015 11:06:25,
> Bernd Linsel wrote: >> For every child in the call chain of a
> function, the local variables >> of the functions above (invoked
> before) seem to be global, as all >> children are accessing the same
> instance of that >> parent's/grandparent's/grand-... local variable.
> >> (Presuming dynamic scoping or nested definitions, like quotations)
> >
> > Dynamic scoping? That's not what you said.
>
> Normally, scope (symbol visibilty) and extent (variable lifetime) in
> Forth don't impose great problems, because nested definitions are not
> allowed. However, when quotations that can be invoked outside the
> creating word's runtime, it must be considered.
>
> Shortly outlined and drastically reduced:
> - Static scope: Nested definitions have access to outer definitions'
> loca ls.
> - Dynamic scope: Nested *invocations* have access to earlier invoked
> functions' locals.
> - Global Forth variables have infinite extent (their value stays valid
> as long as the dictionary is not cleared). - Local Forth variables
> have static extent (their value is valid from their
> definition/initialization until the containing word returns).
>
> Quotations in Forth suddenly introduce nested definitions.
> And if a quotation (q) has somehow access to the locals of the word it
> was defined in (p, for parent), you have a mix of static and dynamic
> scoping:
>
> Static, because q's definition is nested in p's definition. As long as
> you call q from within p, q can just access p's locals stack frame.
>
> But if p returns q (respectively an xt for q) and exits, then q is
> invoked later, p's locals stack frame ceased to exist. Any reference
> to p's locals is invalid. But in q's "history" there has been the
> invocation of p that created q. So now you have a kind of dynamic
> scoping -- iff there is a mechanism that keeps the locals of p alive
> in order to let q access them even after p returned.
> This is not straightforward dynamic scoping after the schoolbook, but
> in
>
> the same category.
This is normally called a closure, hence my confusion.
>
> > <quote>
> > To approximate this behaviour, I suggest making accessed parent's
> loca ls
> > static copies, or if you prefer, globals with special scope, just
> > visible withing the quotation.
> > </quote>
> >
> > and
> >
> > <quote>
> > - parent's locals become 'static locals' when accessed within the
> > quotation, mainly because of the effect of being able to store state
> > (what admittedly may equally be achieved by using globals). >
> </quote> >
> > Can you provide an example or two?
> >
> > On reading agan the post that these come from, I would also like an
> > example of the issues you raise there, since I don't understand it
> > either.
> >
> > <quote>
> > The suggested RfD lacks the possibility for a simple way to pass
> value s
> > into the quotation at creation time (if the parameter stack is used
> as
>
> > compilation stack, as ISO 94 and 200x suggest / allow), and the
> > possibility to create aggregating quotations without a global
> variable
>
> > accessible and visible to the "outer world".
> > </quote>
> >
> > Thanks.
> >
>
> #1 passing values into a quotation
>
> The best example is currying, e.g. reducing the arity of a function by
> providing some (but not all) arguments to it, creating another
> "specialized" function:
>
>: f ( x y -- z )
> dup * \ x y²
> swap * \ y² x²
> +
> ;
>
>: curry { xt1 x -- xt2 }
> [: x swap xt1 execute :] ( y -- z )
> ;
>
>
> # 3 4 f . \ => 25 ok
> # defer f3 \ => ok
> # ' f 3 curry is f3 \ => ok ( f3 is the same as 3 ? f )
> 4 f3 . \ => 25 ok ( 4 f3 is the same as 3 4 f )
>
>
> #2 storing state within a quotation
>
>: begin-sum ( -- xt )
> 0 { sum } \ create local state variable for the sum
> [: sum + dup to sum :] ( n -- sum )
> ;
>
> # defer sum-add \ => ok
> # begin-sum is sum-add \ => ok
> # 3 sum-add . \ => 3 ok
> # 2 sum-add . \ => 5 ok
> # 1 sum-add drop \ => ok ( sum=6 )
> # 4 sum-add drop \ => ok ( sum=10 )
> # 3 sum-add . \ => 13 ok
>
> and...
>
> # begin-sum is sum-add \ => ok ( new instance, sum=0 )
> # : test
> # 10 0 do
> # i sum-add drop
> # loop
> # 0 sum-add ; \ => ok
> # test . \ => 45 ok
>
>
> #3 passing value into the quotation's definition
>
>: begin-sum-with-start { sum -- xt } \ initial value not null but
> provided by caller
> [: sum + dup to sum :] ( n -- sum )
> ;
>
> # 8 begin-sum-with-start is sum-add
> # 1 sum-add drop
> # 2 sum-add drop
> # 3 sum-add . \ => 14 ok
>
>
>
> Got the point?
I understand what you are illustrating; I don't understand your point. #1
Currying for example (modified from
http://rosettacode.org/wiki/Currying#Forth)
: curry { x xt1 -- xt2 }
:noname x postpone literal xt1 compile, postpone ; ;
5 ' + curry constant plus5
5 plus5 execute .
7 plus5 execute .
This doesn't require quotations.
#2 and #3 can use a global value or variable, and #3 additionally suffers
from a compilation problem I describe to you here
https://groups.google.com/forum/message/raw?
msg=comp.lang.forth/BMSyAsqtrB8/4cOA74DrCAAJ
>
> --
> Best regards,
> Bernd
>
>
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RfD: Quotations "Alex McDonald" <blog@rivadpm.com> - 2015-07-28 21:22 +0100
Re: RfD: Quotations anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-07-29 07:35 +0000
Re: RfD: Quotations "Alex McDonald" <blog@rivadpm.com> - 2015-07-29 14:20 +0100
Re: RfD: Quotations Ron Aaron <rambamist@gmail.com> - 2015-07-29 13:44 +0300
Re: RfD: Quotations "Alex McDonald" <blog@rivadpm.com> - 2015-07-29 13:42 +0100
Re: RfD: Quotations Raimond Dragomir <raimond.dragomir@gmail.com> - 2015-07-29 05:35 -0700
Re: RfD: Quotations anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-07-29 13:34 +0000
Re: RfD: Quotations Raimond Dragomir <raimond.dragomir@gmail.com> - 2015-07-29 07:35 -0700
Re: RfD: Quotations anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-07-29 15:05 +0000
Re: RfD: Quotations "Alex McDonald" <blog@rivadpm.com> - 2015-07-29 16:19 +0100
Re: RfD: Quotations Gerry Jackson <gerry@jackson9000.fsnet.co.uk> - 2015-07-29 21:48 +0100
Re: RfD: Quotations mhx@iae.nl - 2015-07-29 11:13 -0700
Re: RfD: Quotations anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-07-30 13:04 +0000
Re: RfD: Quotations "Alex McDonald" <blog@rivadpm.com> - 2015-07-29 15:07 +0100
Re: RfD: Quotations Raimond Dragomir <raimond.dragomir@gmail.com> - 2015-07-29 07:44 -0700
Re: RfD: Quotations anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-07-29 15:12 +0000
Re: RfD: Quotations "Alex McDonald" <blog@rivadpm.com> - 2015-07-29 16:18 +0100
Re: RfD: Quotations Bernd Linsel <bl1@gmx.com> - 2015-07-29 18:37 +0200
Re: RfD: Quotations "Alex McDonald" <blog@rivadpm.com> - 2015-07-29 17:55 +0100
Re: RfD: Quotations "Elizabeth D. Rather" <erather@forth.com> - 2015-07-29 19:51 -0500
Re: RfD: Quotations Bernd Linsel <bl1@gmx.com> - 2015-07-30 03:31 +0200
Re: RfD: Quotations hughaguilar96@gmail.com - 2015-07-29 19:30 -0700
Re: RfD: Quotations Raimond Dragomir <raimond.dragomir@gmail.com> - 2015-07-29 21:19 -0700
Re: RfD: Quotations Raimond Dragomir <raimond.dragomir@gmail.com> - 2015-07-29 21:37 -0700
Re: RfD: Quotations anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-07-30 11:45 +0000
Re: RfD: Quotations Raimond Dragomir <raimond.dragomir@gmail.com> - 2015-07-30 08:07 -0700
Re: RfD: Quotations anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-07-31 10:54 +0000
Re: RfD: Quotations "Alex McDonald" <blog@rivadpm.com> - 2015-07-31 12:48 +0100
Re: RfD: Quotations Raimond Dragomir <raimond.dragomir@gmail.com> - 2015-07-31 05:40 -0700
Re: RfD: Quotations "Alex McDonald" <blog@rivadpm.com> - 2015-07-31 14:46 +0100
Re: RfD: Quotations "Alex McDonald" <blog@rivadpm.com> - 2015-07-31 14:50 +0100
Re: RfD: Quotations anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-07-31 14:46 +0000
Re: RfD: Quotations hughaguilar96@gmail.com - 2015-07-31 13:16 -0700
Re: RfD: Quotations "Alex McDonald" <blog@rivadpm.com> - 2015-07-31 21:49 +0100
Re: RfD: Quotations hughaguilar96@gmail.com - 2015-07-29 22:42 -0700
Re: RfD: Quotations "Elizabeth D. Rather" <erather@forth.com> - 2015-07-30 08:46 -0500
Re: RfD: Quotations Raimond Dragomir <raimond.dragomir@gmail.com> - 2015-07-29 21:40 -0700
Re: RfD: Quotations "Alex McDonald" <blog@rivadpm.com> - 2015-07-30 10:01 +0100
Re: RfD: Quotations Bernd Linsel <bl1@gmx.com> - 2015-07-30 12:00 +0200
Re: RfD: Quotations "Alex McDonald" <blog@rivadpm.com> - 2015-07-30 11:10 +0100
Re: RfD: Quotations Coos Haak <chforth@hccnet.nl> - 2015-07-30 16:35 +0200
Re: RfD: Quotations anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-07-29 16:53 +0000
Re: RfD: Quotations Bernd Linsel <bl1@gmx.com> - 2015-07-29 19:03 +0200
Re: RfD: Quotations "Alex McDonald" <blog@rivadpm.com> - 2015-07-29 18:24 +0100
Re: RfD: Quotations Bernd Linsel <bl1@gmx.com> - 2015-07-30 01:38 +0200
Re: RfD: Quotations "Alex McDonald" <blog@rivadpm.com> - 2015-07-30 09:10 +0100
Re: RfD: Quotations Bernd Linsel <bl1@gmx.com> - 2015-07-30 12:06 +0200
Re: RfD: Quotations "Alex McDonald" <blog@rivadpm.com> - 2015-07-30 11:21 +0100
Re: RfD: Quotations Bernd Linsel <bl1@gmx.com> - 2015-07-30 14:00 +0200
Re: RfD: Quotations franck.bensusan@gmail.com - 2015-07-30 06:59 -0700
Re: RfD: Quotations "Alex McDonald" <blog@rivadpm.com> - 2015-07-31 10:53 +0100
Re: RfD: Quotations Paul Rubin <no.email@nospam.invalid> - 2015-07-29 10:35 -0700
Re: RfD: Quotations Bernd Linsel <bl1@gmx.com> - 2015-07-30 01:45 +0200
Re: RfD: Quotations Bernd Linsel <bl1@gmx.com> - 2015-07-30 03:17 +0200
Re: RfD: Quotations hughaguilar96@gmail.com - 2015-07-29 19:21 -0700
Re: RfD: Quotations Paul Rubin <no.email@nospam.invalid> - 2015-07-29 23:04 -0700
Re: RfD: Quotations Bernd Linsel <bl1@gmx.com> - 2015-07-30 12:38 +0200
Re: RfD: Quotations "Alex McDonald" <blog@rivadpm.com> - 2015-07-30 12:09 +0100
Re: RfD: Quotations Bernd Linsel <bl1@gmx.com> - 2015-07-30 13:26 +0200
Re: RfD: Quotations "Alex McDonald" <blog@rivadpm.com> - 2015-07-31 09:47 +0100
Re: RfD: Quotations Raimond Dragomir <raimond.dragomir@gmail.com> - 2015-07-31 02:51 -0700
Re: RfD: Quotations "Alex McDonald" <blog@rivadpm.com> - 2015-07-31 11:21 +0100
Re: RfD: Quotations "Alex McDonald" <blog@rivadpm.com> - 2015-07-30 09:11 +0100
Re: RfD: Quotations Paul Rubin <no.email@nospam.invalid> - 2015-07-29 11:36 -0700
Re: RfD: Quotations Paul Rubin <no.email@nospam.invalid> - 2015-07-29 11:37 -0700
Re: RfD: Quotations anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-07-30 13:07 +0000
Re: RfD: Quotations Bernd Linsel <bl1@gmx.com> - 2015-07-30 16:25 +0200
Re: RfD: Quotations mhx@iae.nl - 2015-07-29 11:16 -0700
Re: RfD: Quotations "Alex McDonald" <blog@rivadpm.com> - 2015-07-29 20:27 +0100
Re: RfD: Quotations Gerry Jackson <gerry@jackson9000.fsnet.co.uk> - 2015-07-29 21:57 +0100
Re: RfD: Quotations "Alex McDonald" <blog@rivadpm.com> - 2015-07-29 22:48 +0100
Re: RfD: Quotations Gerry Jackson <gerry@jackson9000.fsnet.co.uk> - 2015-07-31 12:34 +0100
Re: RfD: Quotations "Alex McDonald" <blog@rivadpm.com> - 2015-07-31 13:00 +0100
Re: RfD: Quotations anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-07-31 14:31 +0000
Re: RfD: Quotations mhx@iae.nl - 2015-07-31 11:32 -0700
Re: RfD: Quotations mhx@iae.nl - 2015-07-29 21:42 -0700
Re: RfD: Quotations "Alex McDonald" <blog@rivadpm.com> - 2015-07-30 09:57 +0100
Re: RfD: Quotations hughaguilar96@gmail.com - 2015-07-29 17:21 -0700
Re: RfD: Quotations "Alex McDonald" <blog@rivadpm.com> - 2015-07-30 09:56 +0100
Re: RfD: Quotations franck.bensusan@gmail.com - 2015-07-30 04:15 -0700
Re: RfD: Quotations "Alex McDonald" <blog@rivadpm.com> - 2015-07-30 12:30 +0100
Re: RfD: Quotations franck.bensusan@gmail.com - 2015-07-30 05:04 -0700
Re: RfD: Quotations hughaguilar96@gmail.com - 2015-07-30 13:07 -0700
Re: RfD: Quotations hughaguilar96@gmail.com - 2015-07-29 16:52 -0700
Re: RfD: Quotations "Alex McDonald" <blog@rivadpm.com> - 2015-07-30 09:53 +0100
Re: RfD: Quotations Bernd Paysan <bernd.paysan@gmx.de> - 2015-07-30 21:45 +0200
Re: RfD: Quotations hughaguilar96@gmail.com - 2015-07-30 13:25 -0700
Re: RfD: Quotations Julian Fondren <ayrnieu@gmail.com> - 2015-07-30 15:11 -0700
Re: RfD: Quotations "Alex McDonald" <blog@rivadpm.com> - 2015-07-31 09:11 +0100
Re: RfD: Quotations Gerry Jackson <gerry@jackson9000.fsnet.co.uk> - 2015-07-31 12:04 +0100
Re: RfD: Quotations "Alex McDonald" <blog@rivadpm.com> - 2015-07-30 22:51 +0100
Re: RfD: Quotations hughaguilar96@gmail.com - 2015-07-30 22:38 -0700
Re: RfD: Quotations "Rod Pemberton" <boo@fasdfrewar.cdm> - 2015-07-31 02:10 -0400
Re: RfD: Quotations "Alex McDonald" <blog@rivadpm.com> - 2015-07-31 09:01 +0100
Re: RfD: Quotations hughaguilar96@gmail.com - 2015-08-01 14:59 -0700
Re: RfD: Quotations "Alex McDonald" <blog@rivadpm.com> - 2015-08-01 23:36 +0100
Re: RfD: Quotations Bernd Paysan <bernd.paysan@gmx.de> - 2015-08-02 01:19 +0200
Re: RfD: Quotations hughaguilar96@gmail.com - 2015-08-01 18:27 -0700
Re: RfD: Quotations hughaguilar96@gmail.com - 2015-08-09 14:34 -0700
Re: RfD: Quotations anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-07-31 08:52 +0000
Re: RfD: Quotations "Alex McDonald" <blog@rivadpm.com> - 2015-07-31 11:57 +0100
Re: RfD: Quotations Gerry Jackson <gerry@jackson9000.fsnet.co.uk> - 2015-07-31 21:42 +0100
Re: RfD: Quotations "Alex McDonald" <blog@rivadpm.com> - 2015-07-31 22:25 +0100
Re: RfD: Quotations Gerry Jackson <gerry@jackson9000.fsnet.co.uk> - 2015-07-31 23:39 +0100
Re: RfD: Quotations Gerry Jackson <gerry@jackson9000.fsnet.co.uk> - 2015-08-01 10:59 +0100
Re: RfD: Quotations anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-08-01 14:18 +0000
Re: RfD: Quotations Bernd Paysan <bernd.paysan@gmx.de> - 2015-08-01 22:10 +0200
Re: RfD: Quotations anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-08-02 05:36 +0000
Re: RfD: Quotations Gerry Jackson <gerry@jackson9000.fsnet.co.uk> - 2015-08-03 16:40 +0100
Re: RfD: Quotations "Alex McDonald" <blog@rivadpm.com> - 2015-08-03 18:02 +0100
Re: RfD: Quotations Gerry Jackson <gerry@jackson9000.fsnet.co.uk> - 2015-08-03 20:22 +0100
Re: RfD: Quotations Coos Haak <chforth@hccnet.nl> - 2015-08-04 02:10 +0200
Re: RfD: Quotations Gerry Jackson <gerry@jackson9000.fsnet.co.uk> - 2015-08-04 08:49 +0100
Re: RfD: Quotations hughaguilar96@gmail.com - 2015-08-01 15:15 -0700
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