Groups > comp.sys.acorn.programmer > #914

Re: BBC BASIC, EVAL and PROC

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Date	Mon, 24 Oct 2011 10:07:24 +0100
From	Gavin Wraith <gavin@wra1th.plus.com>
Newsgroups	comp.sys.acorn.programmer
Subject	Re: BBC BASIC, EVAL and PROC
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In message <mpro.ltj5ao09mmcog01il.news@stevefryatt.org.uk>
          Steve Fryatt <news@stevefryatt.org.uk> wrote:

>  You can't call procedures that don't exist, 

Excuse the peripheral relevance. RiscLua does not have a CASE statement
but you can fake one with

 CASE = \(list_of_procs,defaultproc) => \(code,...) 
        local action = list_of_procs[code]
        if action then
           => action(...)
        else
           => defaultproc(...)
        end end end

which copes nicely with procedures with indeterminate
numbers of parameters and undefined procedures. Thus, for example

 wimp_case = CASE (event_handlers, do_nothing)
 
 repeat
  reason_code = sys ("Wimp_Poll",mask,message_block)
  result = wimp_case (reason_code,message_block, user_parameters)
 until exit(result)

shows how the CASE structure can be lifted out of the polling
loop. Incidentally, the "..." is the Lua syntax for an indeterminate 
number of parameters, not metasyntax.

-- 
Gavin Wraith (gavin@wra1th.plus.com)
Home page: http://www.wra1th.plus.com/

Thread

BBC BASIC, EVAL and PROC Michael <michaelremerton@gmail.com> - 2011-10-22 11:15 -0700
  Re: BBC BASIC, EVAL and PROC Steve Fryatt <news@stevefryatt.org.uk> - 2011-10-22 20:20 +0100
    Re: BBC BASIC, EVAL and PROC Michael <michaelremerton@gmail.com> - 2011-10-22 12:54 -0700
      Re: BBC BASIC, EVAL and PROC Steve Fryatt <news@stevefryatt.org.uk> - 2011-10-23 18:44 +0100
        Re: BBC BASIC, EVAL and PROC Michael <michaelremerton@gmail.com> - 2011-10-23 12:45 -0700
        Re: BBC BASIC, EVAL and PROC Gavin Wraith <gavin@wra1th.plus.com> - 2011-10-24 10:07 +0100
    Re: BBC BASIC, EVAL and PROC jgh@arcade.demon.co.uk (Jonathan Graham Harston) - 2011-10-23 19:13 +0100
      Re: BBC BASIC, EVAL and PROC Michael <michaelremerton@gmail.com> - 2011-10-23 12:50 -0700
      Re: BBC BASIC, EVAL and PROC Steve Fryatt <news@stevefryatt.org.uk> - 2011-10-23 22:00 +0100
      Re: BBC BASIC, EVAL and PROC Martin <News03@avisoft.f9.co.uk> - 2011-10-24 18:23 +0100
    Re: BBC BASIC, EVAL and PROC Steve Drain <steve@kappa.me.uk> - 2011-10-24 13:34 +0100
    Re: BBC BASIC, EVAL and PROC Rick Murray <heyrickmail-usenet@yahoo.co.uk> - 2011-10-25 07:34 +0200
      Re: BBC BASIC, EVAL and PROC Nick Roberts <tigger@orpheusinternet.co.uk> - 2011-10-25 18:14 +0100
        Re: BBC BASIC, EVAL and PROC Rick Murray <heyrickmail-usenet@yahoo.co.uk> - 2011-10-26 06:32 +0200
          Re: BBC BASIC, EVAL and PROC druck <news@druck.org.uk> - 2011-10-26 10:51 +0100
            Re: BBC BASIC, EVAL and PROC Rick Murray <heyrickmail-usenet@yahoo.co.uk> - 2011-10-26 19:15 +0200
        Re: BBC BASIC, EVAL and PROC "Ste (news)" <steve@revi11.plus.com> - 2011-10-26 15:09 +0100
          Re: BBC BASIC, EVAL and PROC "John Williams (News)" <UCEbin@tiscali.co.uk> - 2011-10-26 16:36 +0200
            Re: BBC BASIC, EVAL and PROC Rick Murray <heyrickmail-usenet@yahoo.co.uk> - 2011-10-26 19:18 +0200
          Re: BBC BASIC, EVAL and PROC Nick Roberts <tigger@orpheusinternet.co.uk> - 2011-10-26 17:26 +0100
            Re: BBC BASIC, EVAL and PROC "Ste (news)" <steve@revi11.plus.com> - 2011-10-26 21:07 +0100
  Re: BBC BASIC, EVAL and PROC Gerph <gerph@gerph.org> - 2011-10-25 03:28 -0700
    Re: BBC BASIC, EVAL and PROC Ron <beeb@woosh.co.nz> - 2011-10-27 11:52 +1300
      Re: BBC BASIC, EVAL and PROC Theo Markettos <theom+news@chiark.greenend.org.uk> - 2011-10-27 12:00 +0100
        Re: BBC BASIC, EVAL and PROC Ron <beeb@woosh.co.nz> - 2011-10-28 01:38 +1300
          Re: BBC BASIC, EVAL and PROC Theo Markettos <theom+news@chiark.greenend.org.uk> - 2011-10-27 14:02 +0100
        Re: BBC BASIC, EVAL and PROC Rick Murray <heyrickmail-usenet@yahoo.co.uk> - 2011-10-27 18:24 +0200
    Re: BBC BASIC, EVAL and PROC Rick Murray <heyrickmail-usenet@yahoo.co.uk> - 2011-10-27 07:42 +0200
    Re: BBC BASIC, EVAL and PROC Steve Drain <steve@kappa.me.uk> - 2011-11-03 13:57 +0000
      Re: BBC BASIC, EVAL and PROC Tony van der Hoff <news1106@vanderhoff.org> - 2011-11-03 15:28 +0100
        Re: BBC BASIC, EVAL and PROC Steve Drain <steve@kappa.me.uk> - 2011-11-03 16:00 +0000
      Re: BBC BASIC, EVAL and PROC Gerph <gerph@gerph.org> - 2011-11-04 16:22 -0700
        Re: BBC BASIC, EVAL and PROC Steve Drain <steve@kappa.me.uk> - 2011-11-05 14:51 +0000
          Re: BBC BASIC, EVAL and PROC Steve Drain <steve@kappa.me.uk> - 2011-11-06 13:25 +0000
            Re: BBC BASIC, EVAL and PROC Rick Murray <heyrickmail-usenet@yahoo.co.uk> - 2011-11-06 19:35 +0100
              Re: BBC BASIC, EVAL and PROC Alan Adams <alan@adamshome.org.uk> - 2011-11-06 18:53 +0000
            Re: BBC BASIC, EVAL and PROC Gavin Wraith <gavin@wra1th.plus.com> - 2011-11-07 14:09 +0000

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