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Groups > comp.lang.forth > #19497

Re: Parallax Propeller

From Paul Rubin <no.email@nospam.invalid>
Newsgroups comp.lang.forth
Subject Re: Parallax Propeller
Date 2013-02-06 00:29 -0800
Organization Nightsong/Fort GNOX
Message-ID <7xfw193kwk.fsf@ruckus.brouhaha.com> (permalink)
References (8 earlier) <a4032a5a-73c6-485e-8ffa-2ec01da40f51@po6g2000pbb.googlegroups.com> <keqoub$in2$1@speranza.aioe.org> <T5GdnUAcdsK9h4zMnZ2dnUVZ_oGdnZ2d@supernews.com> <7xy5f2vcyx.fsf@ruckus.brouhaha.com> <y42dnQvJTLuM4ozMnZ2dnUVZ_tudnZ2d@supernews.com>

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Andrew Haley <andrew29@littlepinkcloud.invalid> writes:
> Sure, but what's your point?  C++ does this, even though it's up to
> you to free the closure.

Here is an idiomatic use of a closure in Python, to make a simple
on-screen GUI keyboard:

    import Tkinter as T
    def press(key): print 'you pressed', key
    T.Tk()
    def make_keyboard():
        for i,cs in enumerate(['qwertyuiop','asdfghjkl;','zxcvbnm,./']):
            for j,c in enumerate(cs):
                T.Button(text=c,command=lambda k=c: press(k)) \
                   .grid(row=i,column=j)
    make_keyboard()
    T.mainloop()

The closure is the callback expression 

   lambda k=k: press(k)

which is a bit ugly because of Python's weird scoping rules, but the
point is that it creates a callable object that wraps the value of k,
and passes that into the bowels of the GUI framework, which squirrels it
away and calls it through some inscrutable mechanism (maybe in another
thread, etc.) when the user presses buttons.  It would be useless if
the closure didn't persist after the make_keyboard call returned.

Python style note: these days it's also possible and maybe nicer to use
functools.partial(press, k).

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Thread

Parallax Propeller Peter Jakacki <peterjakacki@gmail.com> - 2013-01-13 06:37 +0000
  Re: Parallax Propeller MK <mk@nospam.co.uk> - 2013-01-13 10:26 +0000
    Re: Parallax Propeller Peter Jakacki <peterjakacki@gmail.com> - 2013-01-13 12:22 +0000
      Re: Parallax Propeller Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-01-13 07:24 -0600
        Re: Parallax Propeller Peter Jakacki <peterjakacki@gmail.com> - 2013-01-13 13:55 +0000
          Re: Parallax Propeller mhx@iae.nl (Marcel Hendrix) - 2013-01-13 17:13 +0200
            Re: Parallax Propeller Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-01-16 06:23 -0600
              Re: Parallax Propeller Peter Jakacki <peterjakacki@gmail.com> - 2013-01-16 15:01 +0000
                Re: Parallax Propeller Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-01-16 09:12 -0600
                Re: Parallax Propeller Peter Jakacki <peterjakacki@gmail.com> - 2013-01-16 15:36 +0000
                Re: Parallax Propeller Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-01-16 10:59 -0600
                Re: Parallax Propeller Peter Jakacki <peterjakacki@gmail.com> - 2013-01-16 23:38 +0000
                Re: Parallax Propeller Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-01-17 04:04 -0600
                Re: Parallax Propeller Mark Wills <forthfreak@gmail.com> - 2013-01-17 04:52 -0800
                Re: Parallax Propeller Hugh Aguilar <hughaguilar96@yahoo.com> - 2013-01-24 22:48 -0800
                Re: Parallax Propeller Mark Wills <forthfreak@gmail.com> - 2013-01-24 23:10 -0800
                Re: Parallax Propeller Hugh Aguilar <hughaguilar96@yahoo.com> - 2013-01-28 17:42 -0800
                Re: Parallax Propeller "Rod Pemberton" <do_not_have@notemailnotz.cnm> - 2013-02-05 06:05 -0500
                Re: Parallax Propeller Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-02-05 08:41 -0600
                Re: Parallax Propeller Paul Rubin <no.email@nospam.invalid> - 2013-02-05 10:21 -0800
                Re: Parallax Propeller Bernd Paysan <bernd.paysan@gmx.de> - 2013-02-05 21:37 +0100
                Re: Parallax Propeller "Elizabeth D. Rather" <erather@forth.com> - 2013-02-05 10:44 -1000
                Re: Parallax Propeller Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-02-05 15:52 -0600
                Re: Parallax Propeller Paul Rubin <no.email@nospam.invalid> - 2013-02-06 00:29 -0800
                Re: Parallax Propeller Paul Rubin <no.email@nospam.invalid> - 2013-02-06 00:31 -0800
                Re: Parallax Propeller Bernd Paysan <bernd.paysan@gmx.de> - 2013-02-06 19:46 +0100
                Re: Parallax Propeller Paul Rubin <no.email@nospam.invalid> - 2013-02-09 00:11 -0800
                Re: Parallax Propeller anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-02-09 10:25 +0000
                Re: Parallax Propeller Hugh Aguilar <hughaguilar96@yahoo.com> - 2013-02-06 18:26 -0800
                Re: Parallax Propeller Hugh Aguilar <hughaguilar96@yahoo.com> - 2013-02-05 15:07 -0800
                Re: Parallax Propeller Hugh Aguilar <hughaguilar96@yahoo.com> - 2013-02-05 15:49 -0800
                Re: Parallax Propeller "Rod Pemberton" <do_not_have@notemailnotz.cnm> - 2013-02-05 06:04 -0500
                Re: Parallax Propeller Hugh Aguilar <hughaguilar96@yahoo.com> - 2013-02-05 15:21 -0800
                Re: Parallax Propeller rickman <gnuarm@gmail.com> - 2013-01-16 18:09 -0500
          Re: Parallax Propeller Ben Bradley <ben_u_bradley@etcmail.com> - 2013-01-18 21:07 -0500
            Re: Parallax Propeller "Paul E. Bennett" <Paul_E.Bennett@topmail.co.uk> - 2013-01-19 10:06 +0000
              Re: Parallax Propeller Arlet Ottens <usenet+5@c-scape.nl> - 2013-01-19 13:04 +0100
              Re: Parallax Propeller "A. K." <akk@nospam.org> - 2013-01-19 13:22 +0100
                Re: Parallax Propeller Bernd Paysan <bernd.paysan@gmx.de> - 2013-01-19 13:38 +0100
              Re: Parallax Propeller David Brown <david.brown@removethis.hesbynett.no> - 2013-01-19 17:12 +0100
                Re: Parallax Propeller albert@spenarnc.xs4all.nl (Albert van der Horst) - 2013-01-19 16:45 +0000
                Re: Parallax Propeller David Brown <david.brown@removethis.hesbynett.no> - 2013-01-20 17:49 +0100
                Re: Parallax Propeller upsidedown@downunder.com - 2013-01-19 20:54 +0200
                Re: Parallax Propeller Paul Rubin <no.email@nospam.invalid> - 2013-01-19 11:04 -0800
                Re: Parallax Propeller upsidedown@downunder.com - 2013-01-19 23:05 +0200
                Re: Parallax Propeller Mark Wills <markrobertwills@yahoo.co.uk> - 2013-01-20 01:05 -0800
                Re: Parallax Propeller Arlet Ottens <usenet+5@c-scape.nl> - 2013-01-20 12:11 +0100
                Re: Parallax Propeller upsidedown@downunder.com - 2013-01-20 13:53 +0200
                Re: Parallax Propeller upsidedown@downunder.com - 2013-01-20 13:26 +0200
                Re: Parallax Propeller Les Cargill <lcargill99@comcast.com> - 2013-01-19 14:23 -0600
                Re: Parallax Propeller Les Cargill <lcargill99@comcast.com> - 2013-01-19 14:18 -0600
                Re: Parallax Propeller David Brown <david.brown@removethis.hesbynett.no> - 2013-01-20 20:32 +0100
                Re: Parallax Propeller Les Cargill <lcargill99@comcast.com> - 2013-01-20 18:08 -0600
                Re: Parallax Propeller Walter Banks <walter@bytecraft.com> - 2013-01-20 17:12 -0500
                Re: Parallax Propeller Mel Wilson <mwilson@the-wire.com> - 2013-01-20 19:19 -0500
                Re: Parallax Propeller Walter Banks <walter@bytecraft.com> - 2013-01-20 21:12 -0500
                Re: Parallax Propeller David Brown <david@westcontrol.removethisbit.com> - 2013-01-21 09:01 +0100
                Re: Parallax Propeller Walter Banks <walter@bytecraft.com> - 2013-01-21 21:11 -0500
                Re: Parallax Propeller upsidedown@downunder.com - 2013-01-22 09:39 +0200
                Re: Parallax Propeller Mel Wilson <mwilson@the-wire.com> - 2013-01-22 10:14 -0500
              Re: Parallax Propeller Waldek Hebisch <hebisch@math.uni.wroc.pl> - 2013-01-20 02:03 +0000
            Re: Parallax Propeller George Neuner <gneuner2@comcast.net> - 2013-01-19 12:29 -0500
              Re: Parallax Propeller rickman <gnuarm@gmail.com> - 2013-01-23 12:29 -0500
                Re: Parallax Propeller Mark Wills <markrobertwills@yahoo.co.uk> - 2013-01-24 14:03 -0800
                Re: Parallax Propeller Hugh Aguilar <hughaguilar96@yahoo.com> - 2013-01-24 22:55 -0800
                Re: Parallax Propeller Mark Wills <forthfreak@gmail.com> - 2013-01-24 23:03 -0800
                Re: Parallax Propeller Coos Haak <chforth@hccnet.nl> - 2013-01-25 20:02 +0100
                Re: Parallax Propeller Hugh Aguilar <hughaguilar96@yahoo.com> - 2013-01-28 17:13 -0800
                Re: Parallax Propeller David Brown <david@westcontrol.removethisbit.com> - 2013-01-29 09:15 +0100
                Re: Parallax Propeller Anders.Montonen@kapsi.spam.stop.fi.invalid - 2013-01-30 12:19 +0000
                Re: Parallax Propeller David Brown <david.brown@removethis.hesbynett.no> - 2013-01-30 21:18 +0100
                Re: Parallax Propeller Mark Wills <forthfreak@gmail.com> - 2013-01-30 22:57 -0800
                Re: Parallax Propeller Alex McDonald <blog@rivadpm.com> - 2013-01-31 10:38 -0800
                Re: Parallax Propeller Mark Wills <forthfreak@gmail.com> - 2013-01-31 12:34 -0800
            Re: Parallax Propeller Paul Rubin <no.email@nospam.invalid> - 2013-01-19 10:42 -0800
              Re: Parallax Propeller bob@bob.com - 2013-01-19 19:56 -0600
                Re: Parallax Propeller rickman <gnuarm@gmail.com> - 2013-01-23 12:40 -0500
                Re: Parallax Propeller None <vandys@vsta.org> - 2013-01-24 23:26 +0000
                Re: Parallax Propeller Walter Banks <walter@bytecraft.com> - 2013-01-25 11:49 -0500
                Re: Parallax Propeller rickman <gnuarm@gmail.com> - 2013-01-25 09:25 -0500
                Re: Parallax Propeller None <vandys@vsta.org> - 2013-01-25 21:57 +0000
                Re: Parallax Propeller rickman <gnuarm@gmail.com> - 2013-01-26 18:07 -0500
                Re: Parallax Propeller Mark Wills <markrobertwills@yahoo.co.uk> - 2013-01-27 00:50 -0800
                Re: Parallax Propeller Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-01-27 03:30 -0600
                Re: Parallax Propeller Dombo <dombo@disposable.invalid> - 2013-01-27 12:58 +0100
                Re: Parallax Propeller rickman <gnuarm@gmail.com> - 2013-01-28 21:38 -0500
                Re: Parallax Propeller None <vandys@vsta.org> - 2013-01-27 03:09 +0000
                Re: Parallax Propeller rickman <gnuarm@gmail.com> - 2013-01-28 21:51 -0500
                Re: Parallax Propeller None <vandys@vsta.org> - 2013-01-30 02:10 +0000
                Re: Parallax Propeller rickman <gnuarm@gmail.com> - 2013-01-30 18:32 -0500
            Re: Parallax Propeller David Schultz <abuse@127.0.0.1> - 2013-01-20 11:21 -0600
      Re: Parallax Propeller albert@spenarnc.xs4all.nl (Albert van der Horst) - 2013-01-13 16:24 +0000
      Re: Parallax Propeller David Brown <david@westcontrol.removethisbit.com> - 2013-01-14 10:51 +0100
        Re: Parallax Propeller Peter Jakacki <peterjakacki@gmail.com> - 2013-01-16 06:06 +0000
          Re: Parallax Propeller David Brown <david@westcontrol.removethisbit.com> - 2013-01-16 13:43 +0100
            Re: Parallax Propeller Peter Jakacki <peterjakacki@gmail.com> - 2013-01-16 15:27 +0000
      Re: Parallax Propeller Rafael Deliano <rafael_deliano@arcor.de> - 2013-01-15 21:10 +0100
        Re: Parallax Propeller Peter Jakacki <peterjakacki@gmail.com> - 2013-01-16 06:26 +0000
      Re: Parallax Propeller gavino_himself <visploveslisp@gmail.com> - 2013-01-22 06:26 -0800
    Re: Parallax Propeller Peter Jakacki <peterjakacki@gmail.com> - 2013-01-13 12:44 +0000

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