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Groups > comp.lang.forth > #30380

Re: Quotations revisited

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Anton Ertl wrote:

> For now I am happy if many systems implement plain quotations.  If
> some implementor actually does a generally working implementation of
> downward funargs, we can see whether they are useful enough to justify
> their implementation cost.

They'll probably have the impact that you can't do nested functions 
(downward funargs) which outlive their skope.  Downward funargs require some 
sort of trampoline or a similar dynamic structure, and you wouldn't 
implement that on the heap, but inside the corresponding locals frame.  This 
is destroyed when the creating function exits; the quotation isn't.

A case for quotations used in that way is when you want callbacks in an 
asynchronous network protocol.

Variable last-time
: sync-time ( destination -- ) ticks last-time ! req-ticks
  [: ticks last-time @ - 2/ + set-time ;] is reply-ticks ;

You want this sort of stuff be written close together, as it has a logical 
flow, but it's outliving sync-time.

What you can have is quotations and closures share the same syntax.  Both 
can outlive their environment, and the difference is just that the closure 
can access the locals:

: sync-time ( destination -- )  ticks { last-time } req-ticks
  [: ticks last-time - 2/ + set-time ;] is reply-ticks ;

would work with closures.  It for sure would not work with downward funargs, 
unless you add a "wait-for-reply" synchronization inside the function.

-- 
Bernd Paysan
"If you want it done right, you have to do it yourself"
http://bernd-paysan.de/

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Re: Quotations revisited Mark Wills <markwills1970@gmail.com> - 2014-05-13 01:00 -0700
  Re: Quotations revisited Howerd <howerdo@yahoo.co.uk> - 2014-05-13 01:50 -0700
  Re: Quotations revisited Andrew Haley <andrew29@littlepinkcloud.invalid> - 2014-05-13 03:51 -0500
    Re: Quotations revisited Mark Wills <markwills1970@gmail.com> - 2014-05-13 02:25 -0700
      Re: Quotations revisited Andrew Haley <andrew29@littlepinkcloud.invalid> - 2014-05-13 05:08 -0500
        Re: Quotations revisited "Elizabeth D. Rather" <erather@forth.com> - 2014-05-13 07:46 -1000
        Re: Quotations revisited Paul Rubin <no.email@nospam.invalid> - 2014-05-13 11:03 -0700
          Re: Quotations revisited "Elizabeth D. Rather" <erather@forth.com> - 2014-05-13 08:12 -1000
          Re: Quotations revisited Andrew Haley <andrew29@littlepinkcloud.invalid> - 2014-05-13 13:22 -0500
  Re: Quotations revisited stephenXXX@mpeforth.com (Stephen Pelc) - 2014-05-13 09:15 +0000
    Re: Quotations revisited Mark Wills <markwills1970@gmail.com> - 2014-05-13 02:39 -0700
      Re: Quotations revisited Andrew Haley <andrew29@littlepinkcloud.invalid> - 2014-05-13 05:10 -0500
      Re: Quotations revisited stephenXXX@mpeforth.com (Stephen Pelc) - 2014-05-13 11:47 +0000
      Re: Quotations revisited Laurent Laborde <kerdezixe@gmail.com> - 2014-05-13 19:13 -0700
      Re: Quotations revisited Paul Rubin <no.email@nospam.invalid> - 2014-05-13 19:48 -0700
  Re: Quotations revisited Alexander Skobelev <al.skobelev@gmail.com> - 2014-05-13 03:43 -0700
    Re: Quotations revisited anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2014-05-13 12:35 +0000
      Re: Quotations revisited "Alex McDonald" <blog@rivadpm.com> - 2014-05-13 23:56 +0100
        Re: Quotations revisited anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2014-05-14 14:15 +0000
          Re: Quotations revisited "Alex McDonald" <blog@rivadpm.com> - 2014-05-14 20:48 -0400
            Re: Quotations revisited anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2014-05-15 14:16 +0000
      Re: Quotations revisited Alexander Skobelev <al.skobelev@gmail.com> - 2014-05-13 23:30 -0700
        Re: Quotations revisited Paul Rubin <no.email@nospam.invalid> - 2014-05-14 00:32 -0700
          Re: Quotations revisited Alexander Skobelev <al.skobelev@gmail.com> - 2014-05-14 02:02 -0700
            Re: Quotations revisited Paul Rubin <no.email@nospam.invalid> - 2014-05-14 08:02 -0700
              Re: Quotations revisited anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2014-05-14 15:10 +0000
          Re: Quotations revisited Mark Wills <markwills1970@gmail.com> - 2014-05-14 02:09 -0700
            Re: Quotations revisited Mark Wills <markwills1970@gmail.com> - 2014-05-14 02:14 -0700
              Re: Quotations revisited Mark Wills <markwills1970@gmail.com> - 2014-05-14 02:15 -0700
                Re: Quotations revisited Paul Rubin <no.email@nospam.invalid> - 2014-05-14 08:22 -0700
            Re: Quotations revisited Coos Haak <chforth@hccnet.nl> - 2014-05-14 12:04 +0200
        Re: Quotations revisited Andrew Haley <andrew29@littlepinkcloud.invalid> - 2014-05-14 04:11 -0500
        Re: Quotations revisited anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2014-05-14 14:25 +0000
          Re: Quotations revisited Bernd Paysan <bernd.paysan@gmx.de> - 2014-05-14 20:04 +0200
            Re: Quotations revisited anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2014-05-15 13:50 +0000
              Re: Quotations revisited Bernd Paysan <bernd.paysan@gmx.de> - 2014-05-15 16:24 +0200
                Re: Quotations revisited anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2014-05-15 14:40 +0000
                Re: Quotations revisited Mark Wills <markwills1970@gmail.com> - 2014-05-15 10:18 -0700
          Re: Quotations revisited Alexander Skobelev <al.skobelev@gmail.com> - 2014-05-14 21:57 -0700

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