From: Bruce Horrocks via ntg-context <ntg-context@ntg.nl>
To: ntg-context mailing list <ntg-context@ntg.nl>
Cc: Bruce Horrocks <ntg@scorecrow.com>
Subject: Re: How to extend an existing macro to take optional parameters?
Date: Wed, 15 Mar 2023 01:27:44 +0000 [thread overview]
Message-ID: <02F5932D-E387-4C79-AC59-44304CB76311@scorecrow.com> (raw)
In-Reply-To: <7b7e83ac-0e4b-ac37-c1c2-b0e715de837a@freedom.nl>
> On 13 Mar 2023, at 21:39, Hans Hagen via ntg-context <ntg-context@ntg.nl> wrote:
>
> On 3/12/2023 2:24 PM, Bruce Horrocks via ntg-context wrote:
>> I have an existing macro that I'd like to extend.
>> The current definition is \define[3]\mycommand{...} which I'd like to extend to take an optional 4th parameter plus an optional setup parameter.
>> Thus I currently invoke it as:
>> \mycommand{aa}{bb}{cc}
>> and I'd like to be able to extend it so that any of the following can be used:
>> \mycommand{aa}{bb}{cc}
>> \mycommand{aa}{bb}{cc}{dd}
>> \mycommand{aa}{bb}{cc}{dd}[ee]
>> or
>> \mycommand[ee]{aa}{bb}{cc}{dd} % if this is more the ConTeXt way
>> where {dd} is the optional extra parameter and, if it is present, then [ee] can also be optionally added (because it controls how {dd} is printed).
>> If it helps, the actual body of the macro can easily be a call to Lua so it's fine if the function takes 5 params where 4 and 5 can be nil or empty strings.
>> I've trawled through syst-aux.mkiv but it only covers optional numbers of [ ] or { } but not combinations of both (which given the vast numbers of combinations is perhaps not surprising!). Have I missed something obvious that would help me?
> So, four optional with mandate {} plus a fallback to an optional []
>
> \starttext
>
> \tolerant\def\mycommand#=#=#=#=#:[#5]%
> {\ifparameter#1\or(1:#1)\fi
> \ifparameter#2\or(2:#2)\fi
> \ifparameter#3\or(3:#3)\fi
> \ifparameter#4\or(4:#4)\fi
> \ifparameter#5\or[5:#5]\fi}
>
> \startbuffer
> \mycommand{aa}{bb}{cc}
> \mycommand{aa}{bb}{cc}{dd}
> \mycommand{aa}{bb}{cc}{dd}[ee]
> \mycommand{aa}{bb}{cc}
> \mycommand{aa}{bb}{cc}{dd}
> \mycommand{aa}{bb}{cc}{dd}[ee]
> \stopbuffer
>
> \typebuffer
>
> \startlines \getbuffer \stoplines
>
> \stoptext
>
> I'm not saying that it's the best solution, you can add \protected in front of the \def if needed.
>
> Hans
Thanks Hans,
This works well. I'll try and add something to the Wiki but I don't understand how #: does what it does.
Regards,
—
Bruce Horrocks
Hampshire, UK
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prev parent reply other threads:[~2023-03-15 1:27 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-03-12 13:24 Bruce Horrocks via ntg-context
2023-03-13 21:39 ` Hans Hagen via ntg-context
2023-03-14 2:08 ` Alan Braslau via ntg-context
2023-03-15 1:32 ` Bruce Horrocks via ntg-context
2023-03-15 1:27 ` Bruce Horrocks via ntg-context [this message]
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