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Re: xparse and space skipping

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Mon, 16 May 2011 14:49:20 +0200

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 My take would be as follows: 1. As several has observed: for compatibility with LaTeX2e, spaces should normally be skipped. This allows for formatting such as     \foo{apa}         [bepa]         {cepa} 2. Sometimes, an existing command is redefined so that an optional argument is added at the end. In such cases, it may be preferable to make that argument such that it does not skip spaces, for compatibility with existing documents written under the assumption that spaces would not be skipped at that point. In other words, if     \bar{apa} cepa used to have a space, and \bar for some reason in a package needs to be extended to support \bar{apa}[bepa], then \bar{apa} cepa should still have that space. Therefore, the solution should be to provide both, but let the space-nonskipping variants come with a big warning in the xparse documentation, detailing why they are usually inappropriate. In particular, such documentation should suggest the argument order    \bar[bepa]{apa} as preferable to    \bar{apa}[bepa] since package authors are otherwise likely to pick one at random, never even considering the syntactical implications. I also think the spacious formatting     \foo{apa}         {bepa}         {cepa} needs to be mentioned in the documentation, because I'm sure there are plenty of LaTeX users out there who don't know this is normally possible, and therefore would be inclined to assume thight formatting if ever defining commands. That 2e package definitions are likely to say things like \def\bar{%     ...     \foo{apa}%         {bepa}%         {cepa}%     ... } certainly supports the mistaken impression that spaces are not allowed between arguments. Lars Hellström