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From: Harald Oehlmann <wortkarg3@yahoo.com>
Newsgroups: comp.lang.tcl
Subject: Re: support for built-in -opt style options for proc
Date: Tue, 25 Jun 2024 09:01:20 +0200
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Am 25.06.2024 um 08:14 schrieb Christian Gollwitzer:
> Am 24.06.24 um 10:11 schrieb Mark Summerfield:
>> I want to create a couple of procs with these usages:
>>
>> dialog::prepare ?-parent .? ?-modal true? window
>>
> Here is another very simple argument parser: Use "dict merge".
> 
> proc someprocwithargs {args} {
>      set defaults {-parent . -modal false}
>      set options [dict merge $defaults $args]
>      if {[dict size $options] != [dict size $defaults]} {
>          return -code error "Unknown option"
>      }
>      # now use the stuff in options
> }
> 
> To extend by a mandatory argument is left as an exercise to the reader, 
> you basically take off the last element from "args". It is advisable to 
> do it this way, i.e. to make the mandatory argument positional, either 
> in the beginning - then you can simple stuff it before "args" - or at 
> the end. This way, an option can not be confused with a positional 
> argument, and no "--" stuff is needed.
> 
> There have also been LOTS of advanced implementations in pure Tcl around 
> the discussion of TIP 457 
> https://core.tcl-lang.org/tips/doc/trunk/tip/457.md
> 
>      Christian
> 

Great solution, Christian, I appreciate. I use that often, but the "dict 
size" trick is great.

dialog::prepare ?-parent .? ?-modal true? window

What magic Christian writes about "to the reader", withoput error checking:

set window [lindex $args end]
set args [lrange $args 0 end-1]

Thanks,
Harald