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Frank Mittelbach <[log in to unmask]>
Reply To:
Mailing list for the LaTeX3 project <[log in to unmask]>
Sat, 4 May 2013 09:39:33 +0200
text/plain (42 lines)
Am 30.04.2013 11:42, schrieb Lars Hellström:
> IMHO, the notion that "one cannot use \IfNoValueTF at the code level
> because that is a high level command" is utterly bizarre.

not utterly, no :-) but the phrasing is wrong.

> That many
> low-level features should not be exposed in a high-level context is one
> thing, but also doing the converse is usually a sign that one's design
> is flawed somewhere.

right, which I tried to discuss in my other mail

> When a sensible representation of a fundamental
> concept (missing value, boolean true, boolean false, etc.) can be
> exposed at the high level, then that representation should be used also
> at the low level to the extent possible.

yes, that is missing here.

> To me, it is intunitively correct that a \SplitArgument { 2 } { ; } on
> {bar} should yield two NoValues, since clearly two more pieces of data
> were expected but not provided. It also seems that you may want to
> provide some variant of \SplitArgument that supplies default values when
> nothing explicit is given. For \ang{<degree>;<minute>;<second>}, one
> would probably want 0 (i.e., fixed value like for classical \newcommand)
> as default. For \cline{<from>-<to>}, one would probably want the other
> value to be the default (a classical feature of \section and friends).
> So that might be two siblings of \SplitArgument.

This part here is now solely a discussion of what the UI should offer 
and I agree

  - there should be both a split interface that returns "no value" if 
the value is missing
  - and there should be one where defaults can be specified, just like 
they can be specified for single optional arguments